medical_entomology__and_vector_control_ppt[1].ppt

Mekelle university
College of health sciences
School of public health
Department of environmental health science
Course Name : Medical Entomology and Vector Control
Target group: Environmental Health Science
1
st
Year post basic Students
Instructor: Mr. Tsegaluel Abay (BSc,MSc.)

2024 G.C
1

Chapter one
Introduction
Existing problem associated with vectors
•Bites and allergic effects
•This refer briefly to pests that do not transmit pathogens,
•because in some places they are more important and more difficult to control than
vectors,
•Innumerable infestations of biting insects must have occurred without being
reported because inhabitants become desensitized.
• Chironomidae are a pest in scattered places in India, Africa and North America,
and
•on the Nile many people are admitted to hospital with asthma attributed to these
flies.
•The notorious outbreaks of Simulium griseicolle bring many human activities to a
halt.

Transmission of disease
•There is Transmission dynamics of vectors
•In Tahiti an experimental combination of drug therapy and partial mosquito
control have stopped filariasis transmission (WHO Expert Committee on Filariasis,
1962).
•It is hoped that where Simulium damnosum is difficult to control,
•But partial measures may lead to reduction of the serious symptoms of
onchocerciasis.
•however, and it is desirable eventually to stop transmission altogether.
•The number of flies necessary to maintain transmission may vary from place to
place as in the case of plague fleas on rats.
•Season of transmission.
•It is sometimes possible to restrict control measures to a limited transmission
season.
•In Ghana, Marr & Lewis have found little transmission at a time when larviciding
is difficult because the rivers flow intermittently

•Associated pests
• It is sometimes necessary to consider more than one pest at a time,
•An occasional hazard is schistosome infection of people who control mosquitos
and black flies.
•It is sometimes possible to control more than one vector by use of a single
pesticide.
•Thus, a certain molluscicide can kill mosquito larvae (Gretillat, 1962), and
•Residual insecticides for anophelines have been known to affect triatomid vectors
of Chagas' disease (Symes et al., 1962), sandflies, culicine vectors of filariasis,
Aedes aegypti, Xenopsylla cheopis and other pests.
• Information is required, however, about the effect of antimalarial spraying, and
cessation of spraying, on other diseases.

•Secondary vectors
•Secondary vectors of malaria are now attracting attention, and Simulium exiguum
may prove to be a secondary vector of onchocerciasis.
•Spread of vectors and disease.
•Vectors may spread, with disastrous results, as in the case of Anopheles gambiae
in Brazil and Egypt.
•Kala-azar evidently spread to eastern Kenya in recent decades and may extend to
other areas where suitable sandflies now exist without the disease.
•If yellow fever virus reached eastern Asia it would find vectors in the shape of
Aedes aegypti and A. albopictus. So Onchocerciasis may spread into areas now
thinly populated.
•Many people must have carried this long-living parasite from Africa to various
countries,
•in some of which blackflies can transmit other filariae Gambian sleeping sickness
might spread into healthy districts where Glossina tachinoides occurs

CONTROL
In considering measures against any arthropod pest
• it is necessary to decide whether control is practicable or
•whether it is better to remove people from danger,
•to protect them with drugs or repellents, or to destroy the animal reservoir of a
disease.
•If control is feasible it is occasionally advisable to consider the possibility of
eradication.
•Control can be achieved
by modifying the environment,
by applied biological control,
by insecticides,
by sterilizing males or various other new methods, or
 by integrated control

•Public health importance of vectors
•Malaria, yellow fever, typhus fever, epidemic typhus, malaria, onchocerciasis,
leishmaniasis, rabies and schistosomiasis
•are all communicable diseases that are prevalent in Ethiopia.
•All of these are transmitted by vectors.
•Three-quarters of the country is an area of malaria transmission and two-thirds
of the Ethiopian population is at risk from malaria.
•Malaria is the number one illness and cause of human deaths in

kolla
areas of
Ethiopia.
•A number of diarrhoeal diseases (acute watery diarrhoea, dysentery, typhoid
fever)
•can also be transmitted by vectors and are commonly observed among children
in areas where sanitation is very poor.
•Diarrhoea alone kills many children before they get to their fifth year

•Vector-borne diseases
not only cause illness
,
•they also act as a barrier to development.
•Irrigation and dam workers will not be productive if they get malaria or
schistosomiasis (bilharzia or snail fever).
•A person with malaria will need healthcare and will lose productive days at work.
•Some diseases like onchocerciasis (river blindness) have a devastating health
impact.
•If onchocerciasis is left untreated the person could go blind.
•Additionally, vectors like rats destroy food and household materials and weevils
damage cereals.
•The public health importance of vectors can be summarized as follows:
•They cause illness that could be fatal or restrict working capacity.
•They damage food and household goods.
•They are a barrier to development.

Definitions of Terms
Entomology
•Applied Science that study insects (Entomon = Insecta) and other species belonging
to Phylum Arthropoda and its control
Medical Entomology
•A study of the arthropods of medical importance or
•Study of vector, vector borne diseases and abnormalities caused by insects and
their control
•Arthropods: “arthro” means jointed and “poda” means legs
VectorVector
Vector are mostly insects which carry and transmit disease agents from patient to
healthy person; or from disease sources to uninfected food or drinks
9

Vector
Arthropods/other invertebrates which
transmit infection through inoculation of
M/O
s by biting, or
depositing infective materials in the skin,
food or other objects.
10

Modes/ways of diseases transmission
1. Direct contact:
Arthropods are directly transmit diseases from man to man
through close physical contact
Ex. Pediculosis, Scabies
2. Mechanical transmission:
The disease agent is just mechanically carried by the
Arthropod
Ex. Typhoid, Cholera, Dysentery etc. by houseflies
11

2. Biological: When the disease causing organism multiplies
or undergoes changes in the vector.
1. Propagative: Multiplication/increase in number
Plague in fleas, yellow fever in mosquitoes
2. Cyclo –developmental: Cyclical change
 Filariasis
3. Cyclo- propagative: Cyclical changes & multiplication
Malaria
4. Transovarian/ hereditary: Disease transmitted to the
generation by infection of the egg; Tick- borne RF
12

Factors that affect vector effectiveness in diseases
transmission:
1.Receptivity: Ability to support the pathogen to develop
2.Specificity: Exclusive to a specific vertebrate host
3.Longevity: Live a sufficient period of time
4.Frequency of feeding: Nature of vector- host contact
frequency.
5.Mobility: Superior mobility aids in the rapid
dissemination of pathogens over a wide area.
6.Number: Large number increases the chance of feeding
& infecting the host.
7.Physiological & behavioral plasticity: Ability to develop
resistant mechanism by physiological & behavioral
means.
13

14
ARTHROPODS
Compared to the number of species of mammals, protozoa and helminthes, insect
species outnumbers them all
Chapter Two
The arthropods

•Abundance:
•The phylum Arthropoda are dominant (about 78% of all known species of animals)
•Over a million species have been identified.
•They live on land, in the sea and air,
•Major Characteristics
1. Arthropoda means jointed foot. Members of this phylum have jointed
appendages.
These appendages may be modified in a number of ways to form antennae,
mouthparts, and reproductive organs.
2. Arthropods are bilaterally symmetrical
3. They are triploblastic
• arthropods possess a much reduced coelom. However,
•there are larger cavities around the alimentary canal but these are not true coelomic
cavities.
•They are filled by blood and are called hemoeoeles.
15

4. Arthropods have a hardened exoskeleton made of chitin that may
be further stiffened by calcium carbonate (CaC03)
•The exoskeleton is non-expandable and as an individual grows, it
must shed the exoskeleton and replace it with a new larger
exoskeleton. This process is called molting
5. They have segmented bodies, like the annelids.
•Some species show various patterns of segment fusing to form
integrated units. An example is the fusion of the head and thorax to
form the cephalothorax of crayfish.
6. Many have diverse and specialized mouth parts.
7. Arthropods have a well developed ventral nervous system
8. Most possess a dorsal circulatory system
16

Distinctive characteristics of Arthropod
CharacteristicsInsecta ArachnidaCrustacea
1Body division Head, thorax &
abdomen
Cephalo
thorax &
abdomen
Cephalo
thorax &
abdomen
2Legs 3 pairs 4 pairs 5 pairs
3Antennae 1 pair None 2 pairs
4Wings 1 or 2 pairs, None None
5Adult Habitat Terrestrial TerrestrialAquatic
17

Morphology of class insects***
•Introduction
•Morphology: the study of form and function
•Insects are arthropods:
•"jointed feet" Insecta: from insectum; to cut into
• General characteristics of arthropods:
•Segmented bodies Paired,
•segmented appendages
•Bilateral Symmetry
•Exoskeleton
•Dorsal heart and open circulatory system
•Ventral nerve cord
18

•The body is comprised of 3 distinct body regions
•head, thorax, and abdomen
•The thorax of adults bears 3 pairs of legs and 2 pairs of wings
•The "breathing" system is comprised of air tubes or trachea
•A look at the outside of an insect:
•The exoskeleton is comprised of sclerites:
•hardened plates Tergites: Dorsal plates
•Sternites: Ventral plates
•Pleuron: Lateral area, often membranous
19

20

•Sclerites of Head
•Vertex: Summit of the head between compound eyes.
•Frons: Facial area below the vertex and above clypeus.
•Clypeus: Cranial area below the frons to which labrum is attached.
•Gena: Lateral cranial area behind the compound eyes.
•Occiput : Cranial area between occipital an post occipital suture
The integument (body covering)
•is comprised of multiple layers
•The cuticle is the entire outermost layer
•it also lines the air tubes (tracheae, etc.), salivary glands, foregut, and hindgut
21

22
•Strength and resilience (not hardness) are provided by chitin, a nitrogen-
containing polymer common to the arthropods + Caco3

Functions of Head
•Food ingestion
•Sensory perception
•Coordination of bodily activities
•Protection of the coordinating centers
•TYPES OF INSECT HEADS
•Based on the inclination of long axis of the head and orientation of mouth parts there are three types of
insect heads.
•HYPOGNATHOUS (Hypo - below; gnathous - jaw) also called orthopteroid
• The long axis of the head is vertical.
•It is at right angles to the long axis of the body.
•Mouth parts are ventrally placed and project downwards.
23

•PROGNATHOUS (Pro- infront ; gnathous - jaw), also called coleopteroid
•The long axis of the head is horizontal.
•It is in line with the long axis of the body.
•Mouth parts are directed foreward. Eg: groung beetles.
•OPISTHOGNATHOUS (Opistho - behind ; gnathous - jaw) also called hemipteroid
•Head is deflexed.
•Mouth parts are directed backwards and held in between the fore legs. Eg: Stink bug

24

Mouth part of insects and their function
•The mandibulate model :
•Labrum. A plate-like sclerite located before the rest of feeding
structures, protecting them.
•Its size varies among species and it helps to contain the food.
The posterior surface is known as epipharynx.
•Mandibles. A pair of jaws for crushing or grinding the food.
They operate from side to side.
•Maxillae. A pair of appendages which are divided in three parts:
• cardo, which articulates with the head;
•stipes, which supports a sensory palp;
•galea and lacinia, which act as fork and spoon to manipulate the
food.
25

•Hypopharynx
•A little process located behind mandibles and
between maxillae
• helps mix food and saliva.
•Labium. Unlike mandibles and maxillae, the two
original have fused together along the middle.
•The labium is also subdivided in two parts:
•I. Post-mentum, pieces which articulate with the
head;
•II. Pre-mentum, distal pieces which support a pair of
sensory palps and divide apically forming two lobes:
glossae and paraglossae.
26

Method Description Examples
Piercing-sucking Used to penetrate solid tissue and then suck up
liquid food
Cicadas, aphids, sucking lice, stable
flies, mosquitoes
Sponging Used to sponge and suck liquids House fly, blow fly
Chewing Used for biting and grinding solid foodsDragonflies, termites, beetles, ants,
cockroaches, grasshoppers, crickets,
caterpillars
Siphoning Used to suck liquids Bees
27

•STRUCTURE OF INSECT ANTENNAE
•Antennae function almost exclusively in sensory perception.
•information detected by insect antennae includes:
• motion and orientation,
•odor, sound, humidity, and a variety of chemical cues.
•Antennae vary greatly among insects, but all follow a basic plan:
•segments 1 and 2 are termed the scape and pedicel, respectively.
•The remaining antennal segments (flagellomeres) are jointly called the
flagellum
28

•The filament have several segments (pseudo-segments
lacking independent musculature)
A. Setaceous: hair-like
B. And f. Filiform: thread-like
C. Moniliform: bead-like
D. Serrate: sawtoothed
E. Pectinate: comb-like
G. Capitate: headlike (less enlarged at the tip would be
clavate -- clublike)
H. Geniculate: elbowed
I. Lamellate: plate -like
J. Plumose: plumed or feather-like 29

•Eyes of insects
•Compound eyes:
•Individual units are facets or ommatidia.
•in dragonflies 28,000 ommatidia comprise a single compound eye
•Oellus (Ocelli), or simple eyes:
•Very small,
•Usually with a single lens
30

•LEGS AND THEIR MODIFICATION
•The fore-legs are located on the prothorax, the mid-legs on the mesothorax, and
the hind legs on the metathorax.
•Each leg has six major components,
• Coxa (plural coxae),
•Trochanter,
•Femur (plural femora), and tibia (plural tibiae), may has extension spines
•Tarsus (plural tarsi), … appears to be divided into one to five "pseudosegments" called
tarsomeres
•Pretarsus: refers to the terminal segment of the tarsus and any other structures attached
to it
31

•Legs may be modified for specific purposes:
•Jumping: saltatorial -- Eg. grasshoppers, fleas
•Running (or walking): cursorial – Eg. ground beetles, cockroaches
•Clinging: scansorial – Eg. lice, sheep keds
•Grasping (holding prey): raptorial -- Eg. mantids, giant water bugs
•Digging:
fossorial -- Eg. cicada nymphs, mole crickets
•Swimming:
natatorial -- Eg. water scavenger beetle, backswimmer
32

33
•Thorax
•Second and middle tagma which is three segmented
•namely prothorax, mesothorax and metathorax.
•Meso and metathorax with wing are called as Pterothorax.
•Thorax is made up of three scleritic plates namely,
•Dorsal body plate (Tergum or Nota,
•Ventral body plate (Sterna) and
•lateral plate (Pleura).

•The insect abdomen … …
•is comprised of 6 to 10 segments.
•Terminal structures include:
•Cerci: Paired sensory projections from the terminal abdominal segment
•Ovipositor: Egg-laying apparatus (may be modified for other purposes)
•Aedeagus: Male copulatory organ, analogous to the penis in vertebrates
•(Homologous = structures with similar evolutionary origin but different function,
such as the different forms of mandibles in insects.
•Analogous = structures with similar functions but different evolutionary origins,
such as the wings in birds versus insects.)
34

•Inside the insect:
• Digestive System: A tube that extends from the mouth to the anus;
•there are 3 sections:
•Foregut: Pharynx (throat)
Esophagus (gullet)
Crop (storage)
Proventriculus (may be muscled, gizzard-like)
•Midgut:
Gastric caecae (blind sacs) (food storage and enzymes)
Ventriculus (most digestion, absorption here)
•Hindgut: Anterior intestine (excretory organs empty in)
Rectum (reabsorption of water)
Anus
35

•Digestion: Some insects use external digestion in addition that which occurs
internally ...Eg. Leafhoppers inject saliva into plant tissues
House flies regurgitate salivary enzymes onto the surface of food
Diving beetles inject prey with salivary juices
•Most digestive action is in the midgut;
•Gastric caecae are rich in enzymes.
•Enzyme diversity varies with the range of foods that different insects eat ...
•More proteolytic enzymes in blood feeders,
•Cellulase in wood-boring beetles, etc 36

•Fig. Digestive system in insects
37

Growth (Metamorphosis)
•Is- a change in shape and form that some animals, like insects,
undergo during development.
•Although this phenomenon is not restricted to insects, they illustrate
this biological principle better than any other animal group.
•An example of metamorphosis in mosquito. ..
•Eggs are layed in water and hatch into
•Larvae that are commonly called wigglers that transform into Pupae
•Pupae that mature and change to form young
•Young adults that leave the water to become adult mosquitoes
38

A. No metamorphosis
1. These insects have no metamorphosis at all.
2. The young hatch from the egg as the same form as the adult and merely grow larger.
3.Stages of development are EGG ADULT
B. Incomplete metamorphosis
•Some insects like dragonflies, mayflies, and stone flies have a distinctive stage between the egg
and adult called a naiad.
•The naiad bears no resemblance to the adult.
•Eggs are laid in water and hatch into aquatic naiads.
•Naiads grow by successive molts and after the last molt emerge form the water as adults.
•Stages of development are EGG – NAIAD - ADULT
39

C. Gradual metamorphosis
•For insects with this type of metamorphosis the stage between the
egg and adult is called a nymph.
•The nymph usually resembles the adult in general body features,
but it usually lacks wings and genital appendages, (contrast this
with the naiad not resembling the adult)
•Insects with this type of metamorphosis include the grasshopper
and true bugs
•Stages of development are EGG NYMPH ADULT
40

D. Complete metamorphosis
•Many insects undergo complete metamorphosis during their
development.
•The mosquito was our earlier example and it represents a complete
metamorphosis.
•Stages of development are EGG LARVAE PUPAE ADULT
•Each stage is very distinctive and usually very unlike any other stage.
•Perhaps the best example of insects that have complete
metamorphosis are the butterflies.
41

Classification of Phylum Arthropoda
oThe animals included in phylum Arthropoda have different views.
oSo there is no absolute system of classification for this phylum.
oonly three subphyla namely

43

Sub Phylum I: Trilobita (Gr. tri=three, lobos=lobes)
•This subphylum includes extinct arthropods which were abundant
during Paleozoic era.
•These fossil trilobites were exclusively marine bottom dwellers
•Their body can be divided into head, thorax and pygidium(excretion).
•A pair of longitudinal axial furrows divided the body into median axial
lobe and two lateral pleural lobes
•Head was distinct with one pair of antennae and compound eyes.
•All the post-antennal appendages were biramous and unspecialized.
•Examples: Triarthus, Dalmanites

Sub Phylum II: Chelicerata (Gr. chele=claw, keros=horn)
•This subphylum can be divided into two cephalothorax and abdomen.
•The abdomen is further divided into anterior mesosoma and the
posterior metasome.
•Cephalothorax has six pairs of appendages of which the first pair is
chelicerae
•Antennae are absent.
•Subphylum Chelicerata is further divided into the following two classes,
•Class I: Xiphosura (Gr. xiphos=sword, oura=tail)
•Class II: Arachnida (Gr. Arachne =spider)

•Class I: Xiphosura (Gr. xiphos=sword, oura=tail)
•This class included horseshoe crabs. All the genera of this class are
extinct except some endangered.
•Animals of this class are marine in nature
•Cephalothorax bears one pair of chelicerae, four pairs of walking legs
and one pair of pusher legs.
•Mesosomal appendages are modified into a genital operculum and
five pairs of book gills
•They have median Ocilla and lateral compound eyes
•Excretory organs are coxal glands
•Development is indirect and includes trilobite larva.
•Examples: Limulus

Class II: Arachnida (Gr. Arachne =spider)
•The class Arachnids includes a diverse group of arthropods:
spiders, scorpions, ticks, mites, harvestmen, and their cousins.
•Scientists describe over 100,000 species of arachnids
•The first pair of appendages are the chelicerae, also known as the fangs.
•The chelicerae are found in front of the mouthparts and look like modified
pincers.
•The second pair is the pedipalps, which function as sensory organs in
spiders and as pincers in scorpions.
•The remaining four pairs are the walking legs

•Most arachnids are carnivorous, typically preying on insects,
•They are terrestrial, living on land.
•Their mouthparts often have narrow openings,
 which restricts them to eating liquefied prey.
•Arachnids provide an important service, keeping insect populations
under control( acts as biological control)
•Adult arachnids have four pairs of legs, which attach to the
cephalothorax. In immature stages,
•The arachnid may not have four pairs of legs (such as in mites).
•Arachnids lack both wings and antennae.
•Arachnids have simple eyes, called

ocelli. Most arachnids can detect
light or its absence, but don't see detailed images.

•Cephalothorax has one pair or preoral chelicerae, one pair of postoral
pedipalps and four pairs of winged legs.
•The spiders bear fangs with poisonous glands on each chelicera
•Abdominal appendages are modified into book lungs, spinnerets in
spiders, pectin in scorpions etc.
•Excretory glands are coxal glands and Malphigian tubules
•Examples: Palamnaeus, Aranea

•Subphylum III: Mandibulata (L. mandibula=mandible, ata=bearing)
•Mandibles are the first pair of mouth parts
•The first pair of appendages are antennae
•This subphylum is further divided into the following four classes
Class I: Crustaceae (L. Crusta =shell)
•This class includes prawns, crabs, lobsters, crab fishes etc.
•They are mostly marine water dwellers. Few also exist as freshwater
forms.
•Few of these animals are terrestrial but they are not well adapted
• In most of the species the head and thorax fuse to form cephalothorax.

•Cephalic appendages are five pairs namely First antennae, Second
antennae, Mandibles, First maxillae, Second maxillae
•Thoracic appendages are biramous
•Respiration takes place with the help of gills or general body surface in
small forms
•Excretion is through green glands
•Sensory organs include statocysts, compound eyes and antennae
•Most crustaceans have separate sexes, so they reproduce sexually using
eggs and sperm
•Development is direct or indirect involving several larval stages,

Class II: Chilopoda (Gr. chelios =lips, podos=foot)
•This class includes centipedes.
•These animals are terrestrial and carnivorous.
•The body of these animals is divisible into head and trunk.
•They are trignathic with mandibles, first maxillae and second maxillae
•Each segment of the trunk bears one pair of clawed edges.
•Appendages of the first trunk segment bears poisonous claws
•Respiration is through trachea
•Excretory organs are Malphigian tubules
•Centipedes are ophisthogoneate ( mouth is bent to underneath of thorax)
•Examples: Scolopendra, Scutigera

Class III: Diplopoda (Gr. diplos =double, podos=foot)
•This class includes millipedes
•They are terrestrial and detritivorous
•The body is divisible into head and trunk.
•2 pairs of legs per body segment, although some juveniles may posses
only 1 pair per segment
•Simple eyes if present,
•1 pair of antennae
•Chewing mouthparts
•They are assertive with mandibles

•Most of the trunk segments are diplosegments, formed by the fusion of
two segments during development
•Each diplosegments, formed by the fusion of two pairs of legs and two
pairs of spiracles
•Respiratory organs are tracheae
•Excretory organs are Malphigian tubules
•Examples: Spirobolus, Julus

Class IV: Hexopoda (Gr. Hex =six, podos=foot)
•This class is also known as Insecta as it includes insects
•These insects are present in all habitats except the marine habitat.
•The body of the insects is divided into head, thorax and abdomen.
•Thorax bears three pairs of joined legs hence the name Hexapod.
•Respiratory organs are tracheae
•Excretory organs are Malphigian tubules
•Insects are uricotelic. And this is a water conservation adaptation
•Endocrine System: Complex, with hormonal control of sexual reproduction,
development, growth, and communication

•Reproductive System: Dioecious. Gonads one to many. Fertilization
internal (by spermatophores). Oviparous.
•Development: Development may include larval form that is markedly
different from adult.
•Ecology: Mainly terrestrial, a few have returned to water

•Phylum Mollusca
•General features:
•They are commonly called soft bodied animals.
•They are mostly marine, few fresh water and also found in damp soil.
•It is the second largest phylum in the animal kingdom.
•Body is unsegmented (except Neoplina) and bilaterally symmetrical
(except few twisting forms like Pila).
•They have organ system grade
of body organization.
•Body is triploblastic and haemocoelomte.

•Body is divided into three distinct parts; foot for locomotion, head
bears sense organs and visceral mass (digestive and circulatory
organs).
•Body is covered by calcareous shell that may be external (e.g. Pila),
internal (e.g. slug, sea hare, sepia) and absent (e.g. sea lemon,
octopus).
•Glandular fold of the body is called mantle or pallium.
•Mantle cavity or pallial cavity is located between shell and visceral
mass.
•Oshphradium (olfactory organ) are present which that test the
chemical nature of ingoing water current.
•Eyes act as photoreceptors, located on the tip of the tentacles.
•Statocysts are the balancing organs. Tentacles are tactile organs

•The heart is myogenic and dorsally
•Blood is blue in color due to the presence of copper containing
respiratory pigment called Hemocyanin
Excretory system:
•They are ammonotelic.
•One or two pairs of sac like kidneys or organs are present.
•Gills are also excretory in function
•Sexes are generally separate, but some are hermaphrodite.
•Reproduction takes place sexually and development may be direct or
indirect

•Circulatory system is closed or open type
•Excretion takes place by paired metanephridia (kidney).
•Nervous system consists of many paired ganglia, connectives and nerves.
•Sense organs are eyes, tentacles, osphradium and statocyst

Chapter Three
Introduction to the family Culicidae (mosquitoes)
Occurrence
•Mosquitoes -have a world wide distribution.
•Mosquitoes are proven vectors of some of the most devastating human
diseases
•Cause impact on human public health of malaria, yellow fever, filariasis, and
several mosquito-borne diseases of arboviral etiology.
•Rift Valley fever and the equine encephalitis are important livestock diseases
transmitted by mosquitoes
63

• over 2,500 species of mosquitoes have been described worldwide
• 18 genera and subgenera,
•vectors of pathogenic agents are found in the genera Aedes, Culex, Anopheles, and
Mansonia.
•They belong to the class insecta, order diptera family Culicidae,
•which is divided in to three subfamilies toxorhychitnae, anophilinae, culicinae and
•37 genera, and about 3454 species of mosquitoes, of which about 100 are vectors of
human diseases.
•The Anophelinae and the culicinae are blood feeders.
•the toxorhynictinae, do not feed on blood and so we do not concern here.
64

•The most public health important genera are Anopheles, Culex, Aedes, Mansonia,
Hemagogus and Sabethes
External morphology
•Mosquetoes are most important groups of biting dipterans,
•which have:
long slender body
Long needle shaped piercing mouth parts.
Scales on the thorax, legs, abdomen, and wings.
Three pairs of long thin legs.
one pair of functional wing
65

•Mosquitoes are very small (3-6mm)
•have easily fragile physical appearance, and
•they can be sexed by examining their antennae (male-feathery, female-
short, invisible).
•They can be easily identified from other insects by -Mouth parts
•Mouth part is conspicuous and forwardly projected proboscis
•The presence of scales on their abdomen, legs and thorax
•The presence of fringe of scales at the posterior margin of wings.
66

67

Blood feeding and Gonotrophic Cycle
•Female mosquitoes are the one that bite and take a blood meal
•After emerging from pupa they mate shortly and
• Spermatozoa passes from the male to the spermatica of the female
•This sperm fertilize all the eggs that can be laid by the female through out her life
time
•Thus, only one mating and fertilization per female is required
•After mating it is a must for a mosquito to have a blood meal for the eggs to be
matured
•This is the normal procedure and is referred to as anautogenous development
•A few species, however; can develop the first batch of eggs without a blood-meal
•This process is called autogenous development
•After blood meal they have to take a rest for digestion and egg maturation
68

•The speed of digestion of the blood-meal depends on temperature
 In most tropical species takes only 2-3 days,
 In colder, temperate countries may take as long as 7-14 days
•Matured eggs are oviposited at the appropriate place
•Such a repeated process of blood feeding then egg maturation followed
by oviposition through out the females life time is called Gonotrophic
cycle.
69

Life cycle
•The mosquito has four distinct stages : egg, larva, pupa, and adult.
•The adult is an active flying insect,
•while the larvae and pupae are aquatic and occur only in water.
•Depending on the species eggs are laid either
on the surface of water or
are deposited on moist soil or
other objects that will often be flooded
Those species that lay eggs singly on the moist soil usually near the edge of
temporary pools of water are known as flood water mosquitoe
These eggs only hatch after they have been flooded by water.
Psorophora, Aedes, and Ochlerotatus mosquitoes are floodwater mosquitoes
70

•Those species that lay eggs on the surface of the water, (clumped in rafts or as single
floating eggs) are known as permanent water mosquitoes.
•Anopheles, Culiseta, and Culex are permanent water mosquitoes
•The females usually mate only once but produce eggs through out their life.
•to do so most female mosquitoes require a blood meal.
• Male do not suck blood but feed on plant juice
The Eggs
•Many species lay their eggs directly on the surface of water either singly having a boat
shape (Anopheles) or stuck together in rafts (culex) which allow the eggs to float on
the water surface.
•Aedes lay their eggs just above the water line or on wet mud
•These eggs hatch only when flooded with water.
•But The eggs of all mosquitos’ species are not aquatic.
•hatching is affected by many environmental factors especially by temperature.
71

•The Larvae
•Larvae of mosquitoes are active in feeding and in moving.
• They feed on yeast, bacteria, and small aquatic organisms
•They have a siphon located at the tip of the abdomen
•Through which air is taken in and come to the surface of water to breathe
•Anopheles larvae, which feed and breathe horizontally at the surface, have a
rudimentary siphon.
• Larvae of mansonai do not need to come to the surface to breath since they can
obtain air by inserting the siphon in to a water
• In warm climate larval period lasts about 4-7 days.
Pupae
• the fully grown larva changes in to a comma shaped pupa
•Pupae does not feed but spends most of its time at the water surface.
• Unlike most insect pupae it is able to move
72

73

Adult behavior
•The Knowledge of behaviour of mosquitoes governs the selection of
control methods.
•Anopheles are active between sunset and sunrise, usually they become
active at twilight.
•The resting position of adult anopheles is angled or perpendicular where
as culex and aedes rest horizontally with the resting surface.
Feeding Habits
•Female mosquitoes prefer to feed on animals and humans blood
•Mosquitoes are attracted by the body odors, carbon dioxide and heat
emitted from the animal or person
74

•Mosquitoes that bite person to obtain blood meal are called
Anthropophagic and
• those that prefer feeding on non human are called Zoophagic.
•The anthropophagic mosquito can be divided in to:
•endophagic- feed indoor
•exophagic-feed outdoor
•endophilic- rest in indoor
•exophilic- rest in outdoor
75

3.1 Anophelinae (Anopheles Mosquitoes)
External Morphology of Anopheles
•The main features distinguishing anopheles from other mosquitoes have
been given previously, but a brief summary is presented here.
•Most, but not all, Anopheles have spotted wings,
•The dark and pale scales are arranged in small blocks or areas on the veins
•Unlike culicinae the dorsal and ventral surfaces of the abdomen are about
as long as the proboscis and
• in males, but not females, they are enlarged (that is clubbed) apically
76

Life Cycle of Anopheles
•After mating and blood-feeding Anopheles lay some 50-200 eggs
•Those eggs are small brown or blackish boat-shaped eggs singly on the water surface
•There is a pair of conspicuous lateral air-filled chambers called the egg shaft ( help to float)
•Anopheles eggs cannot withstand desiccation and in tropical countries they hatch within 2-
3 days
•but in colder temperate hatching takes bout 2-3 weeks
•Anopheles larvae
•Have a dark brown or blackish sclerotized head,
•A roundish thorax with numerous simple and branched hairs
•A single pair of thoracic palmate hairs dorsally
•Thus, help to maintain the larvae in a horizontal position at the water surface
•lateral to the spiracles is a sclerotized structure bearing teeth resembling a comb and called
the pecten
77

•Have four sausage-shaped transparent anal papillae, which have an osmo-regulatory
function
•Anopheles larvae are filter-feeders
•Unless disturbed remain at the water surface feeding on bacteria, yeasts, protozoa
and other micro-organisms and
•Breath air through their spiracles
•When feeding, larvae rotate their heads 180
0
to sweep the under side of the water
surface.
•Breeding habitat
•Anopheles' larvae occur in less permanent habitats
•Raging from fresh and salt-water marshes, mangrove swamps, grassy ditches, rice
field’s, edges of streams and rivers to pounds and borrow pits
78

•They are also found in small and often temporary breeding places like
puddles, wells, discarded tins and some-times in water-storage pots.
•Some species like exposed sunlight waters whereas others prefer more
shaded breeding places.
•In general, Anopheles prefers clean and unpolluted waters and
•are absent from habitats that contain rotting plants or contaminated with
faeces.
•In tropical countries the larval period frequently lasts only about 7 days
•but in cooler climates the larval period may be about 2-4 weeks.
•In temperate areas some Anopheles as larvae may live many months
79

pupa
•In the comma-shaped pupa the head and thorax are combined to form the
cephalothorax
•cephalothorax has a pair of short trumpet-shaped dorsal breathing tubes
•Remain floating at the water surface with the aid of the pair of palmate hairs on
the cephalothorax
•The pupal period lasts 2-3 days in tropical countries
•sometimes as long as 1-2 weeks in cooler climates
80

Adult Behavior
•Most Anopheleses are crepuscular or nocturnal in their activities.
•Thus blood feeding and oviposition normally occur in the evenings, at night or in the
early mornings around sunrise
•in Africa species of the An. gambiae complex which contains probably the world most
efficient malaria vectors
•These bite mainly after 23.00 hours and mostly indoors (endophilic)
•The times of biting and whether adult mosquitoes are exophagic or endophagic may be
important in the epidemiology of disease.
•Both before and after blood-feeding some species will rest in houses (endophilic)
whereas others will rest outdoors (exophilic)
•Most Anopeles species are not exclusively exophagic or endophagic, exophilic or
endophilic
•exhibit mixture of these extremes of behavior
•few anopheles feed exclusively on either humans or non-humans
•most feed on both people and animals
81

Malaria: Introduction & Lifecycle of Plasmodium
Introduction
• Malaria is a mosquito-borne infectious disease caused by intracellular protozoan
parasite Plasmodium.
• Characterized by cycles of shaking, chills, fever, sweating and anaemia.
• Affects 500 million and kills more than 1 million people each year.
• Endemic in tropical and subtropical regions – Sub-Saharan Africa, Asia and Latin
America.
• In Ethiopia, about 1.5 – 2 million cases and 1000 malarial deaths are reported
annually (mostly from tribal, hilly and inaccessible areas).
82

83

• All forms are transmitted by the infective bite of female Anopheles
mosquitoes.
• Transmission through blood transfusion can also occur.
• Man develops disease after 10 to 14 days of being bitten by an infective
mosquito
84

85

•Lifecycle of Plasmodium
• 2 stages
1) Sexual phase in the mosquito
2) Asexual phase in humans
a) Exoerthrocytic (Pre-erythrocytic) shizogony
b) Erythrocytic shizogony
• The infectious stage of malaria - Sporozoite (found in the salivary glands of
female mosquitoes).
86

Life cycle in humans
• Mosquito takes a blood meal → Sporozoites released into human’s blood →
infect liver cells
• EXO-ERYTHROCYTIC STAGE :
Parasites inside heparocyte → Shizont (containing thousands of
merozoites) → infected hepatocytes release about 30,000 Merozoites
(asexual, haploid forms) → quickly infect red cells.
•* [P. vivax and P. ovale form latent Hypnozoites in hepatocytes, which cause
relapses of malaria long after initial infection]
87

•ERYTHROCYTIC STAGE :
• Within the red cells the parasites grow in a membrane-bound digestive vacuole,
hydrolyzing haemoglobin through secreted enzymes.
• A) Continuation of asexual reproduction –
Most of the parasites develop into Trophozoites → Schizont → multiple
chromatin in schizonts develop into Merozoites → Red cell lysis & merozoites
infect other red cells.
•B) Production of gametocytes –
Some parasites develop into sexual forms called Gametocytes → infect the
mosquito. 88

89

90

3.2 Culicinae
A. Culex Mosquitoes
Distribution
•They are world-wide, but absent in extreme northern temperate zones
Eggs
•The eggs are usually brown, long and cylindrical,
•laid upright on the water surface to form an egg raft( 300 eggs)
•adhesion is due to surface forces holding the eggs together.
• Eggs of a few other mosquitoes, including those of the genus Coquillettidia, are also
deposited their eggs in rafts
•Larvae of culex Mosqueto
•The siphon is often long and narrow
•There is always more than one pair of sub ventral tufts of hairs on the siphon, none of
which is near its base
91

•These hair tufts may consist of very few short and simple hairs if carefully
examined under a microscope.
Adults
•Frequently, but not always, the thorax, legs and wing veins are covered
with somber-colored, often brown, scales.
• The abdomen is covered with brown or blackish scales,
•In some whitish scales may occur on most segments.
• Adults are recognized more by their lack of ornamentation
•The tip of the abdomen of females is blunt.
•The claws of all tarsi are simple and those of the hind tarsi are very small.
•all tarsi have a pair of small fleshy pluvial
92

Biology
•Eggs are laid in a great variety of aquatic habitats.
•Most culex species breed in ground collections of water such as pools,
puddles, ditches, borrow pits and rice fields.
•Some lay eggs in man made container-habitats such as tin cans, water
receptacles, bottles and storage tanks.
•Only a few species breed in tree-holes and even fewer in leaf axils.
•The most important species, culex quinquefasciatus which is a filariasis
vector, breeds
 in waters polluted with organic debris such as rotting vegetation,
household refuse and excreta.
93

•Larvae commonly found septic tanks and in village pots, (polluted and unfit for
drinking).
• It is associated with urbanization, and towns with poor and inadequate drainage and
sanitation.
•Under these conditions its population increases rapidly. Culex tritaeniorhynchus is an
important vector of Japanese encephalitis
•Culex quinquefasciatus, and many other culex species, bite humans and other hosts at
night.
•This culex quinquefasciatus commonly rests indoors both before and after feeding,
•but they also shelter in outdoor resting places
94

1. Annoyance pest :
A mosquito bite may induce local
dermatitis or even systematic
reaction in sensitive persons.
2. Disease Carrier:
Often a carrier of diseases, such
as Filariasis , encephalitis, yellow
fever, dengue fever, dog
heartworm, West Nile virus, and
many others.
The females, who drink blood, can
carry disease from one animal to
another as they feed

B. Aedes Mosquitoes
Distributions
•It has world-wide distribution; their range extends well into Northern and Arctic
areas
• they can be vicious biters and serious pests to people and livestock
•Biology
• Adult and larvae Aedes species breed in marshes and ground pools, including
snow-melt pools in Arctic and sub arctic areas,
•other tropical species, are found in natural or man made container-habitats
•Larvae of Ae. Polynesiensis occur in man made and natural containers,
•larvae of Ae. Pseudoscutellaris are found in tree-holes and bamboo stumps.
•Both of these species are important vectors of diurnal sub perioldic bancroftian
filariasis.
•Aedes togoi, a vector of nocturnal periodic bancroftian and burgian filariasis,
breeds principally in rock-pools containing fresh or brackish water.
96

•The life cycle of Aeds Mosquitoes from eggs to adults can be rapid( 7 days)
•But in Temperate zones usually takes 10-12 days to several week
•Adults of most Aedes species bite mainly during the day or early evening.
•Most biting occurs out of doors and adults usually rest out of doors before and after
feeding.
Eggs
•Eggs are usually black, ovoid in shape and are always laid singly.
•The eggshell has a distinctive mosaic pattern.
•Eggs are laid on damp substrates just beyond the water line,
•such as on damp mud and leaf litter of pools,
•on the damp walls of clay pots, rock-pools and tree-holes.
97

•Aedes eggs can withstand desiccation, can remain dry, but viable, for
many months.
•When flooded, some eggs may hatch within a few minutes, others of the
same batch may require prolonged immersion in water,
•Thus hatching may be spread over several days or weeks
•Even when eggs are soaked for long periods some may fail to hatch
•because they require several soakings followed by short periods of
desiccation before hatching can be induced.
•Even if environmental conditions are favorable, eggs may be in a state of
diapauses and will not hatch until this resting period is terminated.
•Various stimuli including reduction in the oxygen content of water,
changes in day length, and temperature may be required to break
diapauses in Aedes eggs.
98

•Many Aedes species breed in small container- habitats (tree-holes, plant axils, etc)
which are susceptible to drying out,
•Thus, the ability of eggs to withstand desiccation is clearly advantageous.
•Desiccation and the ability of Aedes eggs to hatch in installments can create problems
with controlling the immature stages
Larvae
•Aedes larvae species usually have a short barrel-shaped siphon, and
•There is only one pair of sub ventral tufts which never arise from less than one-quarter
of the distance from the base of the siphon
•Additional characters are at least three pairs of setae in the ventral brush,
•The antennae are not greatly flattened and there are no enormous setae on the thorax
99

•These characters should separate Aedes larvae from most of the culicine genera,
•but not unfortunately from larvae of South American Haemagogus. In central and South
America,
•Aedes larvae distinguished from Haemagogus, by possessing speculate antennae
Adults
•Many, but not all, Aedes adults have conspicuous patterns on the thorax formed by black,
white or silvery scales in some species yellow.
• Scales are present. The legs often have black and white rings
•Scales on the wing veins of Aedes mosquitoes are narrow, and
•are usually more or less all black, except may be at the base of the wing.
•The abdomen is covered with black and white scales forming distinctive patterns, and in the
female it is pointed at the tip.
100

The name comes from the Greek
aēdēs meaning "unpleasant" or
"odious",
 So called because of the diseases
this type of mosquito transmits,
including dengue fever dengue fever and yellow
fever. In Polynesia, the species
Aedes polynesiensis is responsible
for the transmission of human
lymphatic filariasisfilariasis

C. Haemagogus Mosquitoes
Distribution
•Haemagogus is found only in Central and South America
Eggs
•The eggs are black and ovoid and laid singly in tree-holes and other natural container-
habitats, occasionally in human-made ones.
•There is no simple method of distainguishing eggs of Haemagogus from those of Aedes
or psorophora mosquitoes.
Larvae
•Larvae have a single sub-ventral tuft arising, as in Aedes larvae, not less than a quarter
of the distance from the base of the siphon.
•They resemble Aedes larvae but differ by the following characters:
antennae short and either without, or with only very few,
a ventral brush arising from a sclerotized boss.
In some species the comb teeth are at the edge of a sclerotized plate,
 in Aedes this plate is absent.
102

Adults
•Adults are very colorful
•They can easily be recognized by the presence of broad, flat and bright
metallic blue, red, green or golden colored scales, covering the dorsal part
of the thorax.
•Like Sabethes mosquitoes they have exceptionally large anterior pronotal
thoracic lobes behind the head.
•Haemagogus adults are rather similar to Sabethes in other respects,
Biology
•Eggs can withstand desiccation.
•Larvae occur mostly in tree-holes and bamboo stumps,
•but also in rock-pools, split coconut shells and sometimes in assorted
domestic containers.
•They are basically forest mosquitoes
103

•Adults bite during the day, but mostly in the tree tops where they feed on
monkeys.
•they may also descend to the forest floor to bite humans and other hosts.
•Haemagogus spegazzinii, Hg. Equines, Hg. Leucocelaenus (this species was
previously placed in the genus Aedes), Hg. Janthinomys and Hg. apricornii
are all involved in yellow fever transmission in forest areas
104

D. Mansonia Mosquitoes
Distribution
•This is principally a genus of wet tropical areas, but a few species occur in
temperate regions.
Eggs
•Eggs are dark brown-black and cylindrical,
•have a tube-like extension apically which is darker than the rest or the egg.
•Eggs are laid in sticky compact masses, which are glued to the undersurfaces of
floating vegetation.
Larvae
•Mansonia larvae have specialized siphons adapted for piercing aquatic plants
•to obtain air The siphon tends to be conical with the apical part darker
•The siphon has teeth and curved hairs which enable the larva to attach to plants
and insert its siphon.
•Pupae also breathe through plants, by inserting their modified respiratory
trumpets into plants??
105

Adults
•Typically adults have the legs, pulps, wings
•Body covered with a mixture of dark (usually brown) and pale (usually
white or creamy) scales giving the mosquito a rather dusty appearance.
•The speckled pattern of dark and pale scales
•The scales on the wing veins gives the wings the appearance of sprinkled
with salt
•the scales on the wings are very broad and often asymmetrical
• In other mosquitoes these scales are longer and narrower.
106

Biology
•Eggs are glued to plants and hatch within a few days
•They are unable to withstand desiccation
•All larval habitats have aquatic vegetation,
•Larvae occur in armament collections or waters, such as swamps,
marshes, ……
•Adults usually bite during the night,
•but a few species are day-biters.
•After feeding most Mansonia rest out of doors, but a few species rest
indoors.
107

E. Sabethes Mosquitoes
Distribution
•Sabethes mosquitoes are found only in central and South America.
Eggs
•Little is known about the eggs of Sabethes species,
•but it appears that they are laid singly,
•have no prominent surface features such as bosses or sculpturing
•are incapable of withstanding desiccation.
•The eggs of sabethes chloropterus, involved in the sylvatic cycle of yellow
fever, and
• are rhomboid in shape. thus readily identified from other culicine eggs.
108

Larvae
•The siphon has many hairs placed ventrally, laterally or dorsally,
•and is relatively slender and moderately long.
•Sabethes larvae can usually be distinguished by having only one Pair of setae in the
ventral brush,
•the comb teeth arranged in a single row, or at most with 3-4 detached teeth, and by
the absence of a pectin.
Adults
•The dorsal surface of the thorax is blue, green and red scales.
• The anterior pronotal lobes are very large.
•Adults of many species have one or more pairs of tarsi with conspicuous paddles
composed of narrow scales.
• Species, which lack these paddles, resemble those of Haemagogus and a specialist is
required to identify them.
•.
•
109

Biology
•Larvae occur in tree-holes and bamboo stumps
•Few species are found in leaf axils of bromeliads and other plants.
•They are forest mosquitoes. They bite during the day, mainly in the
tree canopy,
•but like Haemagogus adults, may descend to bite humans and other
hosts.
•Sabethes chloropterus has been implicated as a sylvan vector of yellow
fever
110

F. Psorophora Mosquitoes
•The species under the genera psorophora are of minor medical importance
• Psorophora mosquitoes are found only in the Americas, from Canada to South
America.
•They are similar in many respects to Aedes species.
•For example, their eggs look like those of Aedes and they can withstand
desiccation,
•a specialist is required to distinguish the larvae and adults of the two genera.
• Breeding places are mainly flooded pastures and sometimes rice fields
•larvae of several species are predators.
•They can be vectors of a few arboviruses, such as Venezuelan equine
encephalomyelitis,
•their main importance is as vicious biters
• some pest species can be very large
111

112

113

Chapter Four
simuliidae (Black flies)
114
Figure 1.Black fly
larvae

Black flies ( simuliidaea)
•Black ﬂies belong to the family Simuliidae and distributed worldwide
•There are more than 2000 species in 25 genera. However,
•only three genera, Simulium, Prosimulium and Austrosimulium commonly bite
people.
•Medically, Simulium is by far the most important genus as it contains many
vectors.
•In Africa, species in the S. damnosum complex and the S.neavei group, and
•in Central and South America, species in the S.ochraceum, S. metallicum and S.
exiguum complexes,
 transmit the parasitic nematode Onchocerca volvulus, which causes human
onchocerciasis (river blindness).
115

•commonly called "buffalo gnats“,
•because of their humped back appearance.
•dark in color
•appear in a variety of neutral shades from light gray to black.
•They belong to the order Diptera (Flies) and the family Simuliidae.
Onchocerciasis was first reported in southwestern Ethiopia in 1939 by Italian
investigators.
Transmitted by the bites of black flies found near the fast-flowing rivers.
•Endemic areas extend from the northwest to southwest of the country that
borders the Sudan

External morphology of black fly
•Adult black ﬂies are quite small, (1.5–4mm long), relatively stout bodied
•when viewed from the side, have a rather humped thorax.
•As their name indicates they are usually black in color
•but some species have contrasting patterns of white, silvery or yellowish hairs on their bodies
and legs,
•while others may be predominantly orange or bright yellow.
•Black ﬂies have a pair of large compound eyes, which in females are separated on the top of the
head ( a condition known as dichoptic)
•whereas in males the two eyes touch each other and occupy most of the head (a condition
known as holoptic).
•In males, but not females, the lenses of the eyes are larger on the upper half than on the lower
half
117

•The antennae are short, stout, cylindrical and distinctly segmented (usually 11
segments) and lack long hairs.
•The mouthparts are short and relatively inconspicuous,
•Only females bite human to suck blood
•The mouthparts, being short and broad, do not penetrate deeply into the host’s
tissues.
•Teeth on the labrum stretch the skin, while the rasp-like action of the maxillae and
mandibles cuts through the skin and ruptures.
•The small pool of blood produced is then sucked up by the ﬂy.
•This method of feeding is ideally suited for picking up the microﬁlariae of
Onchocerciasis volvulus,
•which occur in human skin, not blood.
118

•The thorax is covered dorsally with very ﬁne and oppressed hair
•Each tarsus has a pair of claws, which are un-toothed (i.e. simple) in mammal-
feeders.
•Wings are characteristically short and broad and lack both scales and prominent
hairs.
•wing is membranous and has indistinct venation
•The wings are colorless or almost so, and when at rest are closed over the body
like the blades of a closed pair of scissors.
•The abdomen is short and squat, covered with inconspicuous closely oppressed
ﬁne hairs.
•In neither sex are the genitalia very conspicuous.
•Black ﬂies are easily sexed by looking to see whether their eyes are dichoptic
(females) or holoptic (males).
119

Life cycle of black fly
• Eggs are about 0.1–0.4mm long, brown or black, and
•Eggs are more or less triangular in shape but have rounded corners and smooth
unsculptured shells
•are covered with a sticky substance. Eggs are always laid in ﬂowing water,
•but the type of larval habitat differs greatly according to species.
•Habitats trickles of water, slow-ﬂowing streams, lake outlets and water ﬂowing
from dams to fast-ﬂowing rivers and rapids.
•Some species prefer low land streams and rivers whereas others are found in
mountain
•Females lay 150–800 eggs in sticky masses or strings on partially immersed
objects such as rocks, stones and vegetation to.
•Larvae are sedentary for long periods on submerged vegetation, rocks, stones and
other debris.

•Attachment is achieved by the posterior hook-circlet
•tightly gripping a small silken pad which has been produced by the larva’s very
large salivary glands and which is ﬁrmly glued to the substrate.
•Larvae can nevertheless move about.
•Larvae normally orientate themselves to lie parallel to the ﬂow of water with their
heads downstream.
•They are mainly ﬁlter-feeders, ingesting, with the aid of large feeding brushes,
suspended particles of food in water
•Depending on species and temperature, larval development may be as short as 6–
12 days, some species several months,
•Mature larvae has a blackish mark termed a gill spot (respiratory organ of the
future pupa) on each side of the thorax

•These larvae spin, with the silk produced by their salivary glands, a protective
slipper-shaped brownish cocoon.
•After weaving the cocoon the enclosed larva pupates
•The pupa has a pair of thin-walled respiratory gills, which are usually prominent
and may be ﬁlamentous or broad.
•In both tropical and non-tropical countries the pupal period lasts only 2–6 days
and is unusual on temperature.
•On reaching the water surface the adults immediately take ﬂight.
•The empty pupal cases, with gill ﬁlaments still attached, remain enclosed in their
cocoons
•After the adults have emerged and provide a means of identifying simuliid species
that have successfully emerged.
•A few African and Asian black ﬂy species have a very unusual aquatic association

Adult behavior of black flies
• Both male and female black ﬂies feed on plant juices and naturally occurring sugary substances,
• but only females take blood-meals.
•Biting occurs out of doors during the day.
•Many species, including S. damnosum in Africa, have bimodal biting patterns
•When feeding on animals, adults crawl down the fur of mammals,
•Many species of black ﬂy feed almost exclusively on birds (ornithophagic),
•others on non-human mammalian hosts (zoophagic),
•while several species also bite people (anthropophagic).

•After feeding, blood-engorged females shelter in vegetation, on trees and in other
natural outdoor resting places until the blood-meal is completely digested.
•In the tropics this takes 2–3 days, while in non-tropical areas it may take 3–8 days
or longer,
•the speed of digestion depending mainly on temperature.
•A few species can lay eggs without a blood-meal ….. Autogenous
•Females of some species may ﬂy considerable distances (15–30 km) from their
emergence sites to obtain blood-meals.
•Adults of S. damnosum move 60–100 km from their larval habitats, and
•Affects control programmes, because areas freed from black ﬂies can be reinvaded
from distant larval habitats.

Medical importance of black flies
I.Annoyance
• In both tropical and non-tropical regions black ﬂies cause very serious biting
problems.
•severity of the reaction is localized swelling and inﬂammation frequently occurs,
•However, it is as disease vectors that black ﬂies are most important medically.
II. Onchocerciasis (river blindness)
•is a non-fatal disease,
•Pathogenic ﬁlarial parasite Onchocerca volvulus.
•There are no animal reservoir hosts, so the disease is not a zoonosis.
•Worldwide 37 million people are infected, of whom about 300 000 are blind
orpartially blind in 37 countries where the disease is endemic.
•About 99% of all cases occur in 30 countries in West Africa, Central Africa and
much of East Africa

•Black
ﬂies are the only vectors of human
onchocerciasis.
•Their habit during feeding of tearing and rasping the skin to rupture blood
ingestion of the skin-borne micro
ﬁlariae of
O. volvulus.
•Most micro
ﬁlariae ingested during feeding are destroyed or excreted,
•but some penetrate the stomach wall and migrate to the thoracic muscles.
•Here they develop into sausage-shaped stages (called L1 larvae), then molt to L2
stage larvae,
•a few of which molt again to become elongate and thinner L3 worms which pass
through the head and down the proboscis
•Upon feeding infective third-stage worms (about 660 μm in length) leave the
proboscis and penetrate the host’s skin
•The interval between the ingestion of micro
ﬁlariae and the time when infective
larvae (L3) are in the proboscis is about 6–12 days, depending on temperature

•African vectors of onchocerciasis Chromosomal studies show that
•……. the S. damnosum complex is composed of about 57 cytoforms,
•The S. damnosum species complex is widespread in tropical Africa, and
some of the species are the most important vectors of onchocerciasis
Control of black flies
•Some protection can be gained by using repellents such as DEET, or
•by wearing pyrethroid-impregnated or sprayed clothing.
•But apply insecticides to larval habitats effective
•These need be applied to only a few selected sites on water courses for some
15–30 minutes,
•Because as the insecticide is carried downstream it kills simuliid larvae
• Flow rates of the water and its depth are used to calculate the quantity of
insecticide to be released.

•In the past dosing rivers with DDT has given good control of S. damnosum in
Africa,
•but because of its accumulation in food chains DDT is no longer used.
•Nowadays insecticides such as temephos or Bacillus israelensis(Bti) are
often used.
•Treatment has to be regularly repeated, sometimes at intervals of 1–2
weeks, throughout the year to prevent re-colonization.
•application of larvicides is difficult (size of the rivers and inaccessible
watercourses)
•Under these conditions aerial applications from small aircraft or helicopters
may be appropriate.

Quiz 1 (5%)
Write your name and ID. No first!
1. Write any think that you know about black fly?
2. Describe Diapause condition in flies?
3. Explain is the difference between Autogenous and Anautogenous?
4. The most medically important genus of black fly vectors is ____?
A. Simulium B. Prosimulium C. Austrosimulium D. All
5. The expression for black ﬂy that exclusively feed on birds is _____ ?
A. Ornithophagic B. Zoophagic C. Anthropophagic D. all
6. in Africa, the disease onchocerciasis, that caused by Onchocerca volvulus, is transmitted by the
vector ____?
• S.ochraceum
• S. metallicum
• S. Neavei
• S. exiguum

Chapter Five
Phlebotominae (sand ﬂies)
•Within the subfamily Phlebotominae of the family Psychodidae
•there are more than 1000 species and subspecies of sand ﬂies,
•Three genera – Phlebotomus, Lutzomyia and Sergentomyia – suck blood from
vertebrates,
•the former two are important because they contain disease vectors
•Sergentomyia species mainly found in the Indian subregion, sub-Saharan Africa
and Asia.
•Although a few species bite people they are not vectors.
•Sand ﬂies are vectors of leishmaniasis and viruses responsible for sand ﬂy fever,
and in the Andesthe bacterium, Bartonella bacilliformis, causing bartonellosis
(Carrión’s disease).
•Adult ﬂies are often called sand ﬂies because of their colour.

External morphology of sand fly
•Adults of Phlebotomus and Lutzomyia are difﬁcult to distinguish,
•Adult phlebotomine sand ﬂies are readily recognized by their
• minute size (usually less than 5mm long),
• hairy appearance,
• relatively large black eyes and long and stilt-like legs.
• Phlebotomine sand ﬂies have the head, thorax, wings and abdomen densely
covered with long hairs.
•antennae are long and composed of small bead-like segments having short hairs;
•antennae are similar in both sexes.
•conspicuous and droop downwards.

•The mouthparts are short and inconspicuous and adapted for blood-sucking,
• but only females bite.
•At their base is a pair of ﬁve-segmented maxillary palps which are relatively
•Wings are lanceolate in outline and distinct from the wings of other biting ﬂies.
•The Phlebotominae can be distinguished their wings.
•wings are held at an angle of about 40 degrees over the body when the ﬂy is at rest
or blood-feeding,
•whereas in non-biting psychodid ﬂies they are held ﬂat across the body.
•Wing venation also differs in phlebotomine sand ﬂies,
•The abdomen is moderately long and in female rounded at the tip.
•In males it terminates in a prominent pair of genital claspers

•which give the end of the abdomen an upturned appearance.
•Identiﬁcation of adult phlebotomine sand ﬂies to species is difﬁcult
•usually necessitates the examination of internal structures,
•such as the ….. arrangement of the teeth on the cibarial armature,
• ……. the shape of the spermatheca in females, and
• ……… in males the structure of the external genitalia(terminalia).
Life cycle
•The minute eggs (0.3–0.4mm) are more or less ovoid in shape and
•usually brown or black, and
•careful examination under a microscope reveals that they are patterned,
•Some 30–70 eggs are laid singly at each oviposition.

•They are thought to be deposited in small cracks and holes in the ground,at the
base of termite mounds, in cracks in masonry, on stable ﬂoors, in poultry houses,
amongst leaf litter
•Eggs are not laid in water, they require a microhabitat with high humidity.
•They are unable to withstand desiccation and hatch after 4–20 days,
•hatching may be delayed in cooler weather.
•Larvae are mainly scavengers, feeding on organic matter such as fungi.
•Although Phlebotomus occur in semiarid areas, the actual larval habitats must
have a high degree of humidity.
•Larvae may be able to survive by migrating to drier areas if their breeding places
are temporarily ﬂooded.

•There are four larval instars.
•The mature larva (3–6mm ) and has a well-deﬁned black head
•the body is white or greyish and has 12 segments.
•Ventrally the abdominal segments have small pseudopods,
•First-instar larvae have two single bristles, not two pairs.
•Larval development is usually completed after 20–30 days,
•the duration depending on the species, temperature and availability of food.
•In temperate and arid regions sand ﬂies may enter diapausing
•The larval skin is not completely cast off but remains attached to the end of the
pupa.
•The presence of this skin aids in the recognition of the phlebotomine pupa.
•Adults emerge from the pupae after about 6–13 days

•The life cycle, from oviposition to adult emergence, is 30–60 days,
•but extends to several months in some species with diapausing larvae.
•Adult behavior
•Both sexes feed on plant juices and sugary secretions, but females in addition suck
blood from a variety of vertebrates
•Biting is crepuscular and nocturnal periods, but some time darkened rooms
•Are exophagic but also feed indoors (endophagic).
•A few species are autogenous
•Adults are weak ﬂiers and usually disperse 100 m from their larval habitats.

• Medical importance
A. Annoyance
•About 70 species are vectors of disease to humans,
•sand ﬂies may constitute a serious but usually localized biting nuisance.
•In the Americas up to 100 bites per night have been recorded.
B. Leishmaniasis
•Due to 30 distinct species, subspecies and strains of Leishmania parasites.
•Worldwide there are about 1–2 million cases a year, with about 12 million people
currently infected in 88 countries.
•The three main clinical forms are cutaneous, mucocutaneous and visceral
leishmaniasis.
•A fourth, less common form is diffuse cutaneous leishmaniasis,
•whilepost-kala-azar dermal leishmaniasis is caused by Leishmania donovani

•Cutaneous
leishmaniasis(CL)
–L. tropica
–L. major
–L. aethiopica
–L. panamensis
–L. guyanensis
–L. peruviana
138
Visceral
leishmaniasis(VL)
L. donovani
L. infantum
L. Chagasi
Mucocutaneous
leishmaniasis(MCL)
L. panamensis
L. guyanensis
L. Brazilliensis
Diffuse cutaneous
leishmaniasis(DCL)
•L. amzonensis
•L. aethiopica

•In Ethiopia
–Four species of Leishmania are found, namely,
▪L. aethiopica,
▪L. major
▪L. tropica
▪L. donovani
•The disease is widely spread in different area in Ethiopia:
• Gondar, Tigrai, Jimma, Diredawa, Lekempt, Harar, Arbaminch, Dessie.
139

•I. Cutaneous leishmaniasis (CL)
• areas of the Middle East to northwestern India and central Asia, in North Africa
and various areas in East, West and southern Africa.
•The principal parasites are Leishmania major,
•transmitted mainly by Phlebotomus papatasi, and
•Le.tropica, transmitted by P.sergenti.
•Leishmania major is usually zoonotic
•Le.tropica occurs in densely populated areas
•and humans appear to be the main reservoir hosts.
•CL is found mainly in forests from Mexico to northern Argentina, and
• is caused by Leishmania braziliensis, Le. amazonensis and Le. mexicana.
•Rodents and dogs appear to be reservoir hosts.

II. Mucocutaneous leishmaniasis (ML) (espundia)
• A severely disﬁguring disease found from Mexico to Argentina.
•mainly caused by Leishmania braziliensis.
•Dogs may be reservoir hosts.
•Lutzomyia wellcomei is an important vector.

•III. Diffuse cutaneous leishmaniasis (DCL)
•A form that causes wide spread cutaneous nodules or macules over the body.
•It is conﬁned to Venezuela and the Dominican Republic and the highlands of
Ethiopia and Kenya.
•In South America the parasite is Le. amazonensis, transmitted by Lutzomyia
ﬂaviscutellata, and
•spiny rats (Proechimys species) are reservoir hosts.
• In Ethiopia and Kenya the parasite is Le. aethiopica, transmitted by Phlebotomus
pedifer and P. longipes,
•Rock hyraxes (Procavia capensis) as reservoir hosts.

IV. Visceral leishmaniasis (VL)
•Often referred to as kala-azar.
•Caused by Leishmania donovani
•Donovaniin most areas of its distribution, Sudan, East Africa and Ethiopia.
•Vectors are Phlebotomu sargentipes and P.orientalis.
•Rodents, wild cats and genets (Genetta genetta) may be reservoir hosts.
•incubation period
•generally 2-6 months
•can range 10 days to years
•fever, malaise, weakness
•wasting despite good appetite
•spleeno- and hepatomegaly,
•enlarged lymph nodes

C. Bartonellosis
•Sometimes called Oroya fever or Carrión’s disease,
•Is encountered in arid mountainous areas of the Peru, but also in Ecuador and
Colombia.
•It is caused by the bacterium Bartonella bacilliformis and
•is transmitted in Peru by Lutzomyia verrucarum and L. peruensis, and by L.
colombiana in Colombia,
•Transmission is possibly only by contamination of the mouthparts.
• Apart from humans there are no other vertebrate reservoir hosts.

Prevention and control
•Most cases of CL heal without treatment, leaving the person immune to
further infection.
•In many parts of South-west Asia, infections were deliberately
encouraged on the buttocks of babies in order to immunize them
(avoiding disfiguring scars on the face or elsewhere).
•Prevent sand fly bites through the repellents and Insecticides.
•residual sprays applied to walls, screens, fences, etc.

Chapter Six
Muscidae (House Fly)
•There are some 18000 species of true
ﬂies
•(sometimes called calyptrate Diptera),
•Medically important species in the families, the Muscidae and Fanniidae,
•The Muscidae contains about 4200 species of
ﬂies in 190 genera.
•The medically most important are
•the common house
ﬂy (
Musca domestica),
•the greater house
ﬂy (
Muscina stabulans)and
•the stable
ﬂy (
Stomoxys calcitrans),
•The lesser or little house
ﬂy and the latrine ﬂy
(Fannia species)
•House
ﬂies can be vectors of helminths, faecal bacteria, protozoans and viruses,
•resulting in the spread of enteric diseases (e.g. dysenteries and typhoids).
•The stable
ﬂy is a biting pest.

•The family Fanniidae comprises about 280 species in four genera,
•Only genus Fannia, such as F. canicularis (lesser house
ﬂy) and F. scalaris (latrine
ﬂ
y), are of medical importance, and like house ﬂies
The common house
ﬂy
(Musca domestica)
•Bout 70 species of
ﬂies in the genus Musca.
•The most common is M.domestica, which is almost worldwide but is least common in Africa,
•where it is largely replaced by two subspecies (M. domestica curviforceps and M. domestica
calleva).
•Other important species are
•(1) the marketplace
ﬂy(Musca sorbens),… nuisance in Africa, Asia and the Paciﬁc,
•(2) the troublesome bush
ﬂy(M. vetustissima) of Australia and
•(3)the face
ﬂy(M. autumnalis),… worlde wide. The appearance and biology of these Musca
species are very similar. The morphology and biology of the house
ﬂy(M. domestica) are
described here.

•External morphology
•House
ﬂies are medium-sized non-metallic ﬂies about 6–9mm long,
•varying in colour from light to dark grey with some darker markings.
•They have four rather broad black longitudinal stripes on the dorsal surface of the
thorax
•The antennae( three segments) are masked in depressions on the front of the
face.
•Each antenna consists of, the distal and largest of which is cylindrical and has a
prominent hair, called an arista, which has hairs on both sides.
•Proboscis are specially adapted for sucking up
ﬂuid or semiﬂuid foods.
•When not in use they are partially withdrawn into the head capsule
•The proboscis ends in a pair of oval-shaped
ﬂeshy labella, having very ﬁne
channels called pseudo-tracheae through which
ﬂuids are sucked up.

•House
ﬂies feed on many types of substances, including almost all food of
humans, rotting vegetables carcasses, excreta and vomit
•– in fact almost any organic material.
•The method of feeding differs according to the physical state of the food.
•For example,
•for thin
ﬂuids, such as milk and beer
, the labella are placed in contact with food,
which is then sucked up through small openings in the pseudo-tracheae.
•When feeding on semisolids such as excreta, sputum and nasal discharges, the
labella are completely inverted and food is sucked up directly in to the food
channel.
•When
ﬂies feed on more
solid such as sugar lumps, dried blood, cheese and
cooked meats, the labella are everted and minute prestomal teeth surrounding
the food channel are exposed and scrape the solid food

•The
ﬂy then moistens small food particles with either
saliva or the regurgitated
contents of its crop so that food can be sucked up.
•This latter type of feeding is clearly conducive to the spread of a variety of
pathogens.
•All three pairs of legs end in paired claws and a pair of
ﬂeshy pad-like structures
called the pulvilli,
•which are supplied with glandular hairs.
•These sticky hairs enable the
ﬂy to adhere to very smooth surfaces, such as
windows.
•They are also responsible for the
ﬂy picking up pathogens when it visits excreta,
septic wounds,

•Life cycle
•Female Musca domestica lay their eggs on decomposing materials such as animal
manure, poultry dung, urine-contaminated bedding, carcasses,, household
garbage and waste foods from kitchens.
•75–150 eggs are deposited together, or in separate batches.
• A
ﬂy may lay eggs 5–10 times in her lifetime, sometimes up to 1000 eggs.
•The eggs are creamy-white, 1–1.2mm long, and distinctly concave dorsally, giving
them a banana shaped appearance
•They can hatch after only 10–16 hours, but this period is longer in cool weather.
•Hatching is accomplished by the strip of eggs hell between parallel ridges on the
dorsal concave surface lifting up,
• Eggs cannot withstand desiccation and die if they dry out.
•Neither can they tolerate extremes of temperatures, most dying after exposure to
temperatures below 15 °C or above 40 °C.

•Developmental time from egg to adult is about 49 days
•…….. at 16 °C, 25 days
•……….at 20 °C, 16 days
•……….at 25 °C, 10–12 days
•……….at 30 °C and 6–7 days
•Very occasionally at higher temperatures the period can be less than 7 days.
•Immature development ceases at temperatures below 12 °C, and 45 °C is lethal
to the eggs, larvae and puparia.
•The adult
ﬂy escapes from its puparial case by pushing off its anterior end and
crawling out, and after a short period it
ﬂies away.

Medical importance of House flies
•ﬂ
ies can transmit a large number of infections to humans as it visits faeces and
other unhygienic matter and people’s food.
•Pathogens can be transmitted by three possible routes:
(1) By
ﬂies’ contaminated feet, body hairs and mouthparts.
•Most pathogens, though, remain viable on the
ﬂy for less than 24 hours, and there
are usually insuf
ﬁcient numbers to cause a direct infection,
•except possibly with Shigella. However, if pathogens are
ﬁrst transferred to food
they may then multiply suf
ﬁciently to reach the level of an infective dose.
(2) By
ﬂies vomiting on food during feeding
,
which they do frequently.
(3) By defecation,
which often occurs on food.
•This is probably the most important method of transmission.

•More than 100 different pathogens have been recorded from house
ﬂies, and
•At least 65 of them can be transmitted to people.
•With the exception of Thelazia species (eye-worms), transmission is mechanical,
•House
ﬂies can transmit
viruses of polio, infectious hepatitis; rickettsiae of Q
fever (Coxiella burnetii);
•Bacteria such as anthrax, Campylobacter, cholera (Vibrio cholerae), Shigella and
Salmonella, Escherichia coli, Staphylococcus aureus;
•Protozoans including Entamoeba, Cryptosporidium and Giardia.
•In addition, house
ﬂies can carry eggs of a variety of helminths,
•for example Taenia, Ancyostoma, Dipylidium, Diphyllobothrium, Enterobius,
Trichuris and Ascaris.

•Eye-worms (Thelazia species) are rather rare infections of the eye and
•are transmitted biologically by Musca species.
•Fungal infections such as Microsporum canis, causing ‘tinea capitis’ in humans,
have also been found in
ﬂy excreta.
•house
ﬂies do not commonly rest on or near the eyes, they are unlikely to be
important vectors of trachoma (Chlamydia trachomatis).
•Adults of the market place
ﬂy(Musca sorbens) frequently settle on or around the
eyes and transmit trachoma.
•Trachoma endemic areas in their breeding sites, such as human faeces, should be
eradicated or at least greatly reduced.
•There is, however, no true intestinal myiasis in humans
•Seasonal increase of
ﬂy abundance associated with outbreaks of diarrhoeal
diseases

Control methods
•can be divided conveniently into three categories:
•(1) physical and mechanical control
•(2) environmental sanitation
•(3) insecticidal control
Physical and mechanical control
•Prevented from entering buildings by covering doors and openings with plastic
screening having a mesh size of 3–4 strands per centimetre
•Placing curtains of vertical, often colored, strips of plastic or beading in doorways
also helps to keep out
ﬂies.
•Restaurants, food stores and hospitals often mount ultraviolet light-traps on walls
to attract
ﬂie
s, which are then killed by an electric grid.
•Commercially available sticky tapes (‘
ﬂy-papers’), incorporating sugar as an
attractant, can be relatively effective, although unsightly, in catching
ﬂies.

Environmental sanitation
•This aims at reducing house
ﬂy populations by minimizing their larval habitats,
that is source reduction.
•For example,
•domestic refuse and garbage should be placed either in strong plastic bags or in
dustbins with tight-
ﬁtting lids.
•When possible there should also be regular refuse collections, preferably twice
a week in warm countries, to prevent eggs laid in the garbage developing into
adults.
•If household refuse cannot be collected it should be burnt or buried.
•Unhygienic rubbish dumps provide Ideal breeding places for house
ﬂies, and
should be removed.

Larvicides
•Insecticides can be directed against the larvae by spraying the insides of
dustbins, any breeding site
•Usually large volumes (0.5–5 litres/m2) are needed to penetrate the upper 10–
15cm of breeding sites to reach the larvae.
Spraying against adults
•Commercial aerosol spray cans or small hand sprayers can be used indoors to kill
adult
ﬂies.
•Suitable insecticides include organophosphates such as malathion or pyrethroids
such as permethrin.
•There must be care not to contaminate food with insecticides.
•Aerosol applications and space-spraying have virtually no residual effects:

Chapter Seven
Glossinidea (Tsetse flies)
•There are 31 species and subspecies of tsetse ﬂies,
•All tsetse ﬂies belong to the genus Glossina, the genus is the Glossinidae.
•tsetse ﬂies are restricted to sub-Saharan Africa, WestAfrica to Central and East
Africa,
•G. palpalis occurs only in the West African sub-region.
•Tsetse ﬂies are vectors of both human and animal African trypanosomiasis,
•the disease in humans being called sleeping sickness.
•The most important vectors are
•G. palpalis,
•G. tachinoides, G. fuscipes, G. pallidipes and
G. morsitans

•External morphology
•Adults are yellowish or brown-black robust ﬂies that are rather larger (6–14mm) than house
ﬂies.
•Some species have the abdominal segments uniformly coloured,
•Tsetse ﬂies are distinguished from other ﬂies by the combination of
•(1) a rigid forward projecting proboscis and
•(2) a closed cell between wing veins, looks like an upside-down hatchet (i.e. axe, cleaver or
chopper)
•At rest tsetse ﬂies also differ from most ﬂies in having the wings placed over the abdomen
like the closed blades of a pair of scissors
•The proboscis is long, and points forwards from the head.

•When a tsetse ﬂy feeds, saliva containing anticoagulants is pumped down into
the wound formed by the ﬂy.
•A long pair of palps occur dorsally, very close to the proboscis, and lie along
side it
•The ﬁrst two antennal segments are small and inconspicuous
•but the third is relatively large, cylindrical and somewhat banana-shaped.
•Antenna has arista with branched hairs on the upper surface

•Dorsally the thorax has dark brown stripes or patches.
•There are eight abdominal segments, which may be uniformly dark brown or
blackish, or have pale brown or yellowish transverse stripes.
•Because both sexes take blood-meals and can be disease vectors
•Tsetse ﬂies can be sexed by examining the tip of the abdomen.
•In males there is ventrally a prominent raised button-like structure called the
hypopygium,
•Which when unfolded reveals a pair of genital claspers.
•In female ﬂy there is no such button-like protuberance

•Life cycle
•Feeding and reproduction
•Both male and female tsetse ﬂies bite people, domesticated and wild mammals,
and sometimes reptiles and birds.
•Tsetse ﬂies blood-feed about every 2–3 days, in cool may be about every 10 days.
•Feeding is restricted to the daytime, and vision, as well as olfactory cues
emanating from host breath and urine,
•On pale-skinned people, tsetse ﬂies often bite through dark clothing such as
socks, trousers and shorts in preference to settling on the skin.
•During feeding blood sucked up the proboscis passes to the crop and later to the
mid-gut, where digestion proceeds.

•tsetse ﬂies do not lay egg, (larviparous).
•After females have mated and taken a blood-meal a single egg in one of the two
ovaries completes maturation.
•It passes oviduct into the uterus, where it is fertilized by sperm in spermathecae.
•The egg hatches within the uterus after about 3–4 days.
•The uterus has pair of branched secretory glands called milkglands.
•These glands provide the larva with all the food for growth and development.
•Regular blood-meals must be taken for a continuous and adequate provision of
nutrient ﬂuid from the milk gland

• If the ﬂy is unable to feed, the larva may fail to complete its development and as
a consequence be ‘aborted’.
•Larval development takes about 9 days, by which time the third- and ﬁnal-instar
larva is 5–7mm long.
•It is creamy white and composed of 12 visible segments,
•the last of which bears a pair of prominent dark protuberances called the
polypneustic lobes, which are respiratory structures.
•A female containing a fully developed larva appears large
•That show the ﬂy is obviously ‘pregnant’.

•Puparial period is comparatively long, usually 4–5weeks,
• but at high temperatures (30 °C) it may be completed within 3 weeks,
•After completion of puparial development the ﬂy emerges from the puparium,
•During larval development in the female the tsetse ﬂy feeds every 2–3 days.
•The ﬁrst larva is deposited about 16–20 days after the female has emerged from
the puparium;
•In the laboratory female tsetse ﬂies have produced up to 20 offspring,
•Breeding generally continues throughout the year, but in very humid conditions
reproduction may be diminished.
•Maximum population size is usually reached at the end of the rainy season.
•suitable larviposition sites may become restricted and localized.

•Medical importance
•All Glossina species are potential vectors of African trypanosomiasis to
humans.
•However, relatively few species of tsetse ﬂies are natural vectors because many
species rarely, if ever, feed on people.
•It is the behavior of adult tsetse ﬂies and the degree of ﬂy–human contact, and
•in the case of Rhodesian sleeping sickness also the degree of vector contact
with reservoir hosts of the trypanosomes, that establishes whether a tsetse ﬂy is
a vector

•Gambian sleeping sickness
•Gambian sleeping sickness (T. brucei gambiense) is the agent of the disease
•occurs from West Africa through Central Africa to parts of Sudan and
•south wards to Angola and the Democratic Republic of the Congo.
•Glossina palpalis and G. tachinoides are the most important vectors in West
Africa,
•while G. fuscipes is the vector in Central and East Africa.
•This disease is relatively chronic,

•Rhodesian sleeping sickness
•The causative agent of Rhodesian sleeping sickness, T. brucei rhodesiense,
causes a more virulent disease than T .brucei gambiense,
•Death occurring After just weeks or months.
•More or less restricted to Tanzania, Malawi, Zambia, Zimbabwe, Mozambique
and the northern areas ofLake Victoria in Kenya and Uganda.
•Around Lake Victoria, G. fuscipes is the main vector and cattle are important
reservoir hosts.
•This form of sleeping sickness is a zoonosis.

•Control
•Because the larva is retained by the female for almost all of its life, and the
puparium is buried in the soil, control of tsetse ﬂies is aimed at the adults.
•Insecticidal control
•Genetic control

Chapter Eight
Siphonaptera (Fleas)
•There are about 2500 species and subspecies of ﬂeas in about 220 genera,
•About 94% of species bite mammals, the remainder are parasitic on birds.
•Fleas occur almost worldwide, but many have a more restricted distribution;
•the genus Xenopsylla, which contains important plague vectors, is conﬁned to
the tropics and warmer parts of some temperate countries.
•Medically the most important ﬂeas are Xenopsylla species,
•such as X.cheopis, which is a vector of plague(Yersiniapestis) and
•ﬂea-borne murine typhus (Rickettsia typhi).

•Fleas in the genus Ctenocephalides may be intermediate hosts of cestodes
(Dipylidium caninum, Hymenolepis diminuta).
•Fleas may also be vectors of tularaemia (Francisella tularensis), and the
chigoe or jigger ﬂea (Tunga penetrans) ‘burrows’ into people’s feet.

•External morphology
•Adult ﬂeas are more or less oval in shape and relatively small (1–6 mm);
•They are compressed laterally and vary from light to dark brown
•Wings are absent,
•but there are three pairs of powerful legs,
•with the hind legs specialized for jumping.
•The legs, and much of the body, are covered with bristles and small spines.
•The head is approximately triangular, bears a pair of conspicuous eyes
•The mouth parts point downwards.

•In some species well-developed tooth like spines, ( comb or genal ctenidium) In
female ﬂeas the tip of the abdomen is more rounded than in males and is not
upturned as in males.
•abdominal segments are one or two distinct brownish spermathecae
•both sex take blood-meals and can be vectors.
•A sensory dome-shaped structure having setae, called the sensilium,
•It is present dorsally and aids ﬂeas in detecting vibrations and temperature
changes as well as in host detection

•Life cycle
•Both sexes take blood-meals and are important as disease vectors.
•female rodent ﬂea leaves the host and deposits her eggs in debris which
accumulates in the host’s dwelling place, such as rodent burrows.
•Eggs are very small (0.1–0.5 mm), oval, white or yellowish and lack any visible
pattern.
•Adults commonly live for 10 days to 6 weeks, but sometimes for 6–12 months or
even longer.
•During her lifetime a female may lay 300–1000 eggs,
•mostly in batches of 3–25 a day

•Eggs hatch after 2–5 days, but this depends on the species of ﬂea, temperature and humidity.
•A minute legless larva emerges from the egg
•It has a small brownish head with a pair of very small antennae,
•Each segment has a circle of setae near the posterior border.
•The last segment ends in a pair of ﬁnger-like ventral processes termed anal struts.
•struts and setae are unique to other insects of medical importance.
•Larvae are very active.
•They avoid light, and shelter in cracks and amongst debris on ﬂoors of houses
•larvae are found on people who wear dirt-laden clothes, and sometimes in beds.
•Larvae feed on almost any organic debris,

•Three larval instars, but in a few species there are only two instars (e.g. Tunga penetrans, ).
•The larval period is commonly 2–3 weeks, but varies according to species, and
•May be prolonged to 200 days or
•more by un favorable conditions such as limited food supply and low temperatures.
•Mature larvae are 4–10 mm long.
•Unlike adult ﬂeas, larvae die if relative humidity is either too low or too high.
•The life cycle from egg to adult emergence may be as short as2–3weeks
• but frequently the life cycle is considerably longer, taking many months
•Fleas avoid light and are usually found sheltering amongst the hairs or feathers of their hosts, or
•on people under their clothing or even in beds.

•During feeding ﬂeas eject faeces composed of semi-digested blood of the previous meal
•This mixture of partially digested and virtually undigested blood often marks clothing and bed
linen of people heavily infested with ﬂeas.
•Most ﬂeas will in fact bite other hosts in their immediate vicinity when their normal hosts are
absent or scarce.
•Although feeding on less acceptable hosts keeps ﬂeas alive, their fertility can be reduced.
•Fleas rapidly abandon dead hosts to ﬁnd new ones,
•behaviour which is of profound epidemiological importance in plague transmission.
•Some ﬂeas can withstand both considerable desiccation and prolonged periods of starvation

•for example
•six months or more, when no suitable hosts are present.
•However, cat and dog ﬂeas die with in 10 days away from their hosts.
•On a host, ﬂeas move by rapidly crawling,
•Where as off the host they jump more than crawling their search for new hosts.
•Some ﬂea species can jump about 20 cm vertically and 30 cm or more horizontally.
•Such remarkable acts are achieved through a rubber-like protein called resilin.
•This is very elastic and can become highly compressed; rapid expansion of the
compressed state gives the power for jumping

•Medical importance
•Flea nuisance
•Although vectors of disease, they may result in considerable discomfort and irritation.
•The most common nuisance ﬂea is the cat ﬂea (Ctenocephalides felis),
•Of lesser importance as apest is the dog ﬂea (Ctenocephalides canis) and
•more rarely the human ﬂea (Pulex irritans).
•People who become hypersensitive to ﬂea bites can suffer from dermatitis, and
•In halationof ﬂea faeces can cause allergies.
•Children under 10 years feel greater discomfort from ﬂea bites than older people.
•People attacked by ﬂeas frequently spend sleepless nights alternately scratching themselves and
trying to catch the ﬂeas.

•Plague
•There are three main types of plague, bubonic, septicemic and pneumonic,
•All caused by the bacterium Yersinia pestis.
•The most important is bubonic plague,
•Bubonic plague is a zoonosis, being primarily a disease of wild animals, especially rodents.
•The transmission cycle of plague between wild rodents is termed sylvatic, campestral, rural or
enzootic plague.
•Many different species of ﬂeas bite rodents and maintain plague transmission amongst them.
•When people such as fur trappers and hunters handle these wild animals there is the risk that
they will get bitten by rodent ﬂeas and become infected with plague.

•Murine typhus
•Also known as endemic typhus or Mexicantyphus,
•The agent is bacterium Rickettsia typhi, which is ingested by a ﬂea with its blood-meal.
•In the gut the rickettsiae multiply,
•Transmission occurs when infected faeces come into contact with delicate mucous membranes,
•Murine typhus is essentially a disease of rodents,
•Its spread among rats and other rodents by Xenopsylla species, especially X. cheopis,
• A few ecto-parasites which are not ﬂeas are vectors,
•such as the spined rat louse (Polyplax spinulosa) and
•possibly the cosmo-tropical rat mite (Ornithonyssus bacoti).

•Control of
ﬂeas
•Repellents such as DEET or permethrin-impregnated clothing may afford some
personal protection against ﬂeas.
•Insecticide resistance has been reported in cat ﬂeas, human ﬂeas and
•Xenopsylla species to one or more of the following categories of insecticides:
•organochlorines, organophosphates, carbamates, pyrethrins and pyrethroids.
•Nevertheless, insecticides remain the main tool for ﬂea control, although there
is increasing reliance on insect growth regulators (IGRs).

Chapter Nine
Anoplura (Sucking lice)
•Three types of blood-sucking lice occur on humans,
•the body louse (Pediculus humanus),
•the head louse (Pediculus capitis) and
•the pubic or crab louse (Pthirus pubis).
•Morphologically the body and head lice are virtually indistinguishable.
•All species of lice have a more or less worldwide distribution, more common in temperate
•Body lice are vectors of louse-bornetyphus (Rickettsia prowazekii),
• trench fever (Bartonella quintana) and
• louse-borne relapsing fever (Borrelia recurrentis).

•The body louse (Pediculus humanus)
• External morphology
•Adults are small, pale beige or greyish wingless insects,
•with a soft but rather leathery integument, and are ﬂattened dorso-ventrally
•Males measure about 2–3mm and females about 3–4mm.
•The head has a pair of small black eyes and a pair of short ﬁve-segmented antennae.
•The three thoracic segments are fused together and the legs are stout and well developed.
•The short thick tibia has apically a small spine on its inner side, and the short tarsus ends in a
curved claw
•Hairs of the host, or clothing, are gripped between this tibial spine and tarsal claw

•Mouthparts of the louse differ from blood-sucking insects
• in that they do not form a projecting proboscis,
•but consist of a sucking snout-like projection called the haustellum,
•which is armed on the inner surface with minute teeth that grip the host’s
skin during feeding.
• Blood is sucked up and passes into the stomach for digestion

• Medical importance
•Pediculosis
•Presence of body, head or pubic lice on a person is some times referred to as
pediculosis.
•The skin of people who habitually harbour large numbers of body lice may
become pigmented and tough,
•a condition known as vagabond’s disease, hobo disease or sometimes as morbus
errorum.

•Louse-borne epidemic typhus
•Rickettsiae of louse-borne typhus, Rickettsia prowazekii,
•are ingested with blood-meals taken by both male and female lice,
•Rickettsiae are passed out in the faeces of the louse,
•people become infected when these are rubbed or scratched into abrasions, or
•come into contact with delicate mucous membranes such as the conjunctiva.
•Infection can also be caused by inhalation of the very ﬁne powdered dry faeces.
•Rickettsiae can remain infective in dried louse faeces for about 60 days.

•Louse-borne epidemic relapsing fever
•Borrelia recurrent is ingested with the louse’s blood-meal from a person suffering
from epidemic relapsing fever,
•Louse-borne relapsing fever has disappeared from Europe
•but remains common in Central and East Africa, Sudan, Ethiopia, Afghanistan and
Peru.
•Ethiopia has about 1000–5000 cases annually; this is about 95% of worldwide
infections.
•As with Rickettsia prowazekii, infection is ultimately fatal to the louse

•Trench fever
•Trench fever is caused by Bartonella quintana.
•The bacteria are ingested by the louse during feeding and become attached to the gut cells,
•The disease is conveyed to humans by its faeces coming into contact with skin abrasions or
mucous membranes.
•Bacteria persist for many months, possibly even a year, in dried louse faeces, and
•it is suspected that infection may also commonly arise from inhalation of the dust-
like faeces.
•The disease may be contracted by those who have no lice, but are handling louse-infected
clothing contaminated with faeces

•The head louse (Pediculus capitis)
•External morphology
•Only very minor morphological differences separate body and head lice.
•In practice, lice found on clothing or on the body are invariably body lice, where as those on
the head are head lice.
•Medical importance
•In many areas of the world head lice are a serious public health problem
•there are higher infestation rates in over crowded homes and where hygiene is poor.
•There is little evidence that head lice are natural vectors of the diseases transmitted by body
lice – for example,
•typhus epidemics are always associated with body lice –
•but they may occasionally be minor vectors in some outbreaks of louse-borne relapsing fever

•The pubic louse (Pthirus pubis)
•External morphology
•The pubic louse is smaller (1.3–2mm) than Pediculus species
•In the pubic louse the body is nearly as broad as long, making it almost round.
•All three pairs of legs are more or less of equal size in the body and head louse,
•in the pubic louse the middle and hind-legs are much thicker than the front legs and have
massive claws
•Presence of a broad squat body and very large claws, together with more sluggish movements,
•has resulted in the pubic louse being called the crab louse.

• Medical importance
•There is little evidence that under natural conditions they spread any disease to
humans,
•Severe allergic reactions (pruritus) can develop in response to their bites,
• Small characteristic bluish spots (maculae caeruleae) may appear on infested
parts of the body.
•Infestations of pubic lice are sometimes known as pediculosis pubis or phthiriasis

•Control
•Originally control involved shaving hairs from the body,
•but this method has been replaced by the application of insecticidal lotions.
•Basically insecticides used for head louse control can be used against pubic lice.
•Application of 1% permethrin or 5% malathion should kill nymphs and adults and possibly
eggs,
• Although resistance to pyrethroids has been reported,
•Infestations on the eyelashes can be treated by applying a small amount of a vaseline ointment
or petroleum jelly twice a day for 8–10 days,
•after which the lice can be carefully pulled off

Chapter Ten
Cimicidae (Bedbugs)
•The family Cimicidae includes bedbugs,
• of which two common species feed on humans.
•Cimex lectularius are in tropical and non-tropical countries, but C. hemipterus, the tropical
•It is not easy to separate these two species,
•External morphology
•Adult bedbugs are oval, wingless insects which are ﬂattened dorso-ventrally
•They are about 5–7mm long and when un fed-pale yellow or brown,
•but after a full blood-meal they become a darker‘mahogany’brown.
•The head is short and broad and has a pair of prominent compound eyes

•Medical importance
•Although hepatitis B virus and 27 other pathogens have been recorded in bedbugs
•there is no evidence that they can transmit any infections to people.
•They are therefore not considered as vectors.
•In areas of poor hygiene standards, bedbug infestations can cause considerable distress.
•Some people show little or no reaction to their bites, but others may suffer severe reactions
and have sleepless nights.
•Repeated feedings of large numbers of bedbugs can cause iron deﬁciency in infants and some
elderly people.

•Control
•Insect repellents and insecticide-impregnated bed-nets
•Infested area should be sprayed with the carbamate bendiocarb,
•organophosphates such as malathion, a range of pyrethroids and methoprene.
•Bedclothes and infants’ mattresses should not be treated with insecticides.
•If bedclothes are infested they should be washed in hot water then ironed or dried in the sun.
•Alternatively clothes can be placed in sealed plastic bags and placed in a freezer (–18°C) for 24
hours to kill the bedbugs.
•Commercially available small insecticidal smoke bombs containing insecticides, such as
permethrin, which burn for up to 15 minutes, can be used to fumigate infested premises

Chapter Eleven
Other classes of Medical importance :
•11.1 Ticks
•Dermatosis: inflammation, itching , swelling at site of bite.
•Anemia: blood loss can result from heavy infestation.
•Otoacariasis: infestation of the inner ear canal by ticks that causes
irritation and sometimes secondary infection.
•Tick paralysis (envenomization): Due to the release of toxic
secretions when persons are bitten at the base of the skull.
•Pathogen transmission (virus, rickettsia, bacteria, spirochaete,
protozoa, filarial worms).
199

11.2 Bilharzia Snail:
Include almost all types of freshwater bodies ranging
from small temporary ponds and streams to large lakes
and rivers.
•Within each habitat, snail distribution may be patchy and
detection requires examination of different sites.
•In general, the aquatic snail hosts of schistosomes occur
in shallow water near the shores of lakes, ponds, marshes,
streams and irrigation channels.
200

201

Public health importance:
•Schistosomiasis is one of the most widespread of all
human parasitic diseases, ranking second only to malaria
in terms of its socioeconomic and public health
importance in tropical and subtropical areas.
•Endemic in 74 tropical countries, and over 200 million
people living in rural and agricultural areas are at risk.
•Snails are also important intermediate hosts for Fasciola
species which infects human and animals.
202

203

Snail control:
•Snail control is perhaps employed less often as a means
of combating the disease.
•It remains an important and effective measure, especially
where transmission occurs to a significant extent through
children playing in water.
•Prior to undertaking snail control measures, health
authorities should screen water for the presence of snail
intermediate hosts.
204

Env’ tal management and reduction of snail habitats:
Alteration of water levels and flow rates
•Raising and lowering water levels and increasing flow
rates can disturb snail habitats and their food sources.
•Rapid complete drainage reduces the amount of
vegetation and kills the snails by desiccation.
• This method may be of interest in areas with irrigated
crops.
205

Removal and destruction of snails
•Snails can be removed from canals and watercourses with
dredges and crushed or left to die of desiccation.
•This happens in irrigated areas of Egypt and Sudan as a
beneficial side-effect of efforts to improve the flow of
water by removing mud from canal bottoms .
206

Plants with molluscicidal activities
•Endod is the Ethiopian name for the soap berry
plant Phytolacca dodecandra (Synonyms: P.
abyssinica, Pircunia abyssinica), a member of the
Phytolaccaceae family.
•The distribution in east, west, central, and southern
Africa and parts of South America and Asia.
207

Chapter Twelve
Rodent problem and Infestation
•Rodents are the most diverse order of the mammals, with over 2,200 species.
•They inhabit all continents except Antarctica, and are adapted to a wide habitats.
•Rodents are social animals and have large reproductive potential
•A few species, especially rats and mice, have adapted well to the human environment and the
benefits it offers to them for food and shelter.
•They have become serious pests in all phases of food supply and
•to human health due to these close encounters with the food we eat and the places we live and
work

•Why the concern?
•Carry diseases that can be transferred to human.
•Contaminate food with their hair, droppings and urine, resulting in food poisoning
and spoilage.
•Generate unpleasant odours.
•Carry fleas or ticks which can harm pets or humans.
•Damage materials such as food containers, wood, particle board, insulation and
wiring through gnawing.

•Types of rodents
•The most common types of rodents available every where are:
•The Black Rat (Rattus rattus)
•Brown Rat (Rattus norvegicus)
•House Mouse (Mus musculus).
•These pests will eat rubbish, pet food, food scraps, composts, fallen fruit and nuts,
bird seed and dog faeces.
•Rats can travel up to several house blocks to find water and food.

Rodent borne Disease
•Rodents are reservoirs of a number of human diseases.
•Rodents can act as both intermediate infected hosts or as hosts for arthropod
vectors such as fleas and ticks.
•Rodent populations are affected by weather conditions.
•In particular, warm, wet winters and springs increase rodent populations
•Under climate change scenarios, rodent populations could be anticipated to
increase in temperate zones, resulting interaction between human and rodents
•This perhaps produce higher risk of disease transmission, especially in urban areas

•Salmonellosis
•Rodents can carry

Salmonella
bacteria
that cause illness in both humans
•Infection occurs by consumption of food or water contaminated with rodent
faeces.
•The most common source of infection is by food contaminated with the faeces of
farm animals.
•Genetic studies of

Salmonella
show that it is extremely complex and as a result
has a complex classification.
•There are two species recognised and many sub-species and sub-types, called
serovars:
•Salmonella enterica, which has six subspecies and 2500 serovars, is the main
cause of salmonellosis in humans and other mammals.
•S. bongori
mainly occurs in reptiles, but can infect humans through contact with
pets.

•Leptospirosis
•Leptospirosis is an infection caused by species of Leptospira bacteria.
•It is caught from the urine of infected animals, which include rodents and also
cattle, pigs and dogs.
•Humans can become infected by:
•direct contact with urine or other animal body fluids (except saliva) of infected
animals;
•contact with soil, water or food contaminated with the urine of infected animals.
•The bacteria live inside the animal’s kidneys and are passed out in urine.
•They can survive for weeks or months in soil or water.
•The bacteria can also enter through the skin,
•especially if broken by a scratch or cut, and the mucus membranes of the eyes,
nose and mouth.

•Rat-bite fever
•is caused by two bacteria Streptobacillus moniliformis and Spirillum minus.
•In infected rodents the bacteria are present in rat faeces and urine and secretions
from the mouth, nose and eyes.
•It is usually caused by a bite or scratch from an infected rat or other rodents such
as mice, squirrels and gerbils.
•It can also be caught by handling infected animals and ingesting food or drink
contaminated with rodent faeces or urine.
•Plague
•The plague is the classic disease that is linked to rats in the human environment
•The disease is caused by the bacteria Yersinia pestis, which cycles between
rodents and fleas.
•Several species of rodents are long-term reservoirs of the plague bacteria in the
wild

•Bartonellosis
•Bartonellosis is caused by a number of species of

Bartonella bacteria, several of
which can be carried by rodents and which cause a wide range of symptoms.
•The disease can be transmitted between animals by biting arthropods such as
ticks, fleas, sandflies, lice and mosquitoes.
•Hanta-virus
•Many species of rodent carry hantaviruses, especially rats and mice.
•Arena-viruses
•Arenavirus
is a genus of primitive viruses, in humans that usually show as fever
and acute haemorrhagic illness.
•Some such as

Lassa fever
have high mortality.
•Each of these virus species is associated with a particular rodent species, usually
in a localised geographic region.

•Rat tapeworm
•There are two types of rat tapeworm,

Hymenolepis nana
and
H. diminuta.
•Both species use a beetle (eg a flour beetle) as the main secondary host and are
found in warm climates worldwide.
•H. nana
is the most common as, unusually for helminths,
•it can have a complete lifecycle in human intestines and spread from person to
person through eggs in faeces.
•It attaches to the intestine wall and absorbs nutrients through the cells lining the
intestine.

•Investigation on rodent infestation
•Rodents are generally more active at night and are more common in late
summer/early autumn.
•If you see rats or mice during the day, this usually indicates high numbers or
• that there is a good food supply nearby
•Inspecting for rodent activity, we look for:
Black, moist, thin droppings.

Debris left from rodents gnawing items like snail shells, almond shells and chop
bones.

Food left for pets which has gone missing.
Signs of gnawing damage on fruit, and vegetables or materials such as wood,
insulation and electrical cabling.
‘Runways’ which have formed when rodents have used the same path such as
through vegetation/gardens or along fences.
Greasy rub marks on walls or skirting boards where rodents travel regularly.
Burrow holes close to sheds or under debris.

•Avoiding rodent problems
•Rodents are well adapted to living in human environments.
•To reduce their numbers on your property:

Dispose of food scraps promptly and clean food preparation areas thoroughly.
Inspect living and working areas for potential rodent entrances and block
them where possible with concrete, hard setting filler, steel wool or heavy gauge
sheet metal.
Ensure rubbish bins have tight-fitting lids and are regularly emptied.
Keep your home and property clear of rubbish.

•Protecting yourself from rodent contacts
•If rodents are present:
•secure all foodstuffs in sealed containers
•throw away food or drink that may have come into contact with rodents
•wash cookware and cutlery in warm water and detergent before use
•wash hands thoroughly before preparing food, eating, drinking or smoking
•wear shoes and do not lie or sleep on areas where rodents have been active. If you
are bitten by a rat or mouse, consult your doctor promptly.

•Chemical control
•Chemical control should only be considered as part of a broader control program
of eliminating food sources and rodent harbourage.
•Chemical control is generally short-term and rodents will return if food and
shelter are still available.
•Rat poisons or rodenticides containing an anti-coagulant can be purchased from
market stores.

•Trapping
•Mouse and rat traps differ in size and strength.
•It is important that the type of rodent is identified and the proper trap used. Traps
can be purchased from hardware stores or supermarkets.
•Some tips for setting traps:
•Several traps should be used at one time.
•Do not set traps near food preparation areas.
•Place across ’runways’ for a few days before setting to allow rodents to get used to
the traps.

•Traps can be successfully set with bacon, peanut butter, fish, meat, bread or
chocolate.
•Check traps daily; remove any dead rodents and refresh the bait.
•Use an insecticidal surface spray around the immediate area to kill any fleas
which may leave a trapped rodent’s body.

medical_entomology__and_vector_control_ppt[1].ppt

About This Presentation

Slide Content

Tags

Categories

Download

Quick Actions

Statistics

Related Slideshows

medical_entomology__and_vector_control_ppt[1].ppt

About This Presentation

Slide Content

Slide 1

Slide 2

Slide 3

Slide 4

Slide 5

Slide 6

Slide 7

Slide 8

Slide 9

Slide 10

Slide 11

Slide 12

Slide 13

Slide 14

Slide 15

Slide 16

Slide 17

Slide 18

Slide 19

Slide 20

Slide 21

Slide 22

Slide 23

Slide 24

Slide 25

Slide 26

Slide 27

Slide 28

Slide 29

Slide 30

Slide 31

Slide 32

Slide 33

Slide 34

Slide 35

Slide 36

Slide 37

Slide 38

Slide 39

Slide 40

Slide 41

Slide 42

Slide 43

Slide 44

Slide 45

Slide 46

Slide 47

Slide 48

Slide 49

Slide 50

Slide 51

Slide 53

Slide 55

Slide 56

Slide 57

Slide 58

Slide 59

Slide 60

Slide 61

Slide 62

Slide 63

Slide 64

Slide 65

Slide 66

Slide 67

Slide 68

Slide 69

Slide 70

Slide 71

Slide 72

Slide 73

Slide 74

Slide 75

Slide 76

Slide 77

Slide 78

Slide 79