Helminth introduction

Parasitology

1. INSTITUTE OF PULIC HEALTH, DHAKA Department of Laboratory Medicine BSc in Health Technology (Laboratory)- 1 st Year HELMINTHOLOGY Lecture No. 01(Introduction) By Sk. MIZANUR RAHMAN Assistant Bacteriologist, MBL, IPH MS in Biotechnology & Genetic Engineering (UODA) MS in Microbiology ( SU) MPH in Epidemiology (SUB)

2. Norman Stoll, President of the American Society of Parasitologists 1947 inaugural address “This wormy world” Called for a world-wide effort to control worm infections

3. Method of Learning Terminology Introduction Classification Characteristics Differences between the classes Example and Life cycles

4. HELMINTH/WORM TERMINOLOGY Adults: sexually reproductive life cycle stage Larvae: developmental or asexually reproductive life cycle stage Eggs: stage protective of zygote &/or embryo Cysts: usually a larval stage encapsulated in tissues of an intermediate host Hypobiosis: worms in temporary developmental arrest Monoecious/hermaphroditic: both sexes 1 body Dioecious: sexes separate; males & females Parthenogenesis: ability to produce offspring without fertilization of eggs

5. Helminths, continued Worm-terms, continued Oviparous: production of eggs, discharged from uterus of female Ovoviviparous: production of eggs which hatch prior to discharge from uterus of female Viviparous: production of embryos/L1 larvae, no rigid encapsulation of embryo

6. Introduction to helminth Helminth means worm. Their motile activity is accomplished by wriggling movement. The helminth of medical importance belong to 3 classes: Nematoda , Trematoda and Cestoda . Helminthology  is the study of parasitic worms and their effect on their hosts. Geohelminths refer to the helminths which complete their life cycles not requiring the processes of the development in intermediate hosts. They have only one host and a simple life cycle, such as ascarid , hookworm, pinworm and etc. Biohelminths refer to those that have to undergo the development in intermediate hosts to complete their life cycle , such as filaria , liver fluke, pork tapeworm and so on.

7. Taxonomic classification of helminths Sub kingdom Phylum Class Genus – examples Metazoa Nematodes Round worms; appear round in cross section, they have body cavities, a straight alimentary canal and an anus Ascaris (roundworm) Trichuris (whipworm) Ancylostoma (hookworm) Necator (hookworm) Enterobius (pinworm or threadworm) Strongyloides Platyhelminthes Flat worms; dorsoventrally flattened, no body cavity and, if present, the alimentary canal is blind ending Cestodes Adult tapeworms are found in the intestine of their host They have a head (scolex) with sucking organs, a segmented body but no alimentary canal Each body segment is hermaphrodite Taenia (tapeworm) Trematodes Non-segmented, usually leaf-shaped, with two suckers but no distinct head They have an alimentary canal and are usually hermaphrodite and leaf shaped Schistosomes are the exception. They are thread-like, and have separate sexes Fasciolopsis (liver fluke) Schistosoma (not leaf shaped!)

8. HELMINTHS (WORMS) Characteristics Eukaryotic (N+CW), multicellular animals that usually have digestive, circulatory, nervous, excretory, and reproductive systems. Worms with bilateral symmetry, head and tail, and tissue differentiation (endoderm, mesoderm, and ectoderm). Parasitic helminths spend most or all of their lives in host and usually have the following specializations: May lack a digestive system . Absorb nutrients from host’s food, body fluids, or tissues. Have a reduced nervous system. Means of locomotion is reduced or absent. Complex reproductive system. Individuals produce many eggs that can infect another host.

9. Helminthes   Cestodes Trematodes Nematodes Shape Segmented plane Unsegmented plane Cylindrical Body cavity No No Present Digestive tube No Ends in cecum Ends in anus Sex Hermaphroditic - Taenia (tapeworm) Hermaphroditic, except Schistosoma which are dioecious Dioecious - Ascaris (roundworm) hook organ component Oral sucker, botridias , and double Rostellar hooks Oral sucker and ventral sucker Lips, teeth, filariform extremities, and dentary plates

10. Helminths (Worms): Some Important Ones Most acquired from ingestion of or contact with feces-contaminated soil or food Nematodes (Roundworms): Ascaris lumbricoides GI illness; pneumonitis Trichuris trichuria chronic GI Hookworms: Ancylostoma duodenale chronic anemia Necator americanus chronic anemia Strongyloides stercoralis chronic anemia Cestodes (tapeworms): Hymenolepis nana GI illness Worm burdens tend to be low in the United States; little illness occurs Still major causees of illness in developing countries

11. Examples of important metazoa – intestinal nematodes Trichuris (whipworm) A soil transmitted helminth prevalent in warm, humid conditions Can cause diarrhoea, rectal prolapse and anaemia in heavily-infected people Ancylostoma and Necator (hookworms) A major cause of anaemia in the tropics Strongyloides inhabits the small bowel infection more severe in immunospressed people (e.g. HIV/AIDS, malnutrition, intercurrent disease) Enterobius (pinworm or threadworm) prevalent in cold and temperate climates but rare in the tropics found mainly in children Ascaris (roundworm) Found world-wide in conditions of poor hygiene, transmitted by the faecal- oral route Adult worms lives in the small intestine Causes eosinophilia Heavy intestinal infections may occur with Ascaris . Adult worms can be several cms long.

12. Infective name Pathogenesis stage route Prevention mode Life cycle Pathogenic name Pathogenesis stage localization Treatment migration Diagnosis Diagnostic stage-morphology Diagnosis stage methods stage outside name Epidemiology (vector, other host) name Prevention Learning method