Ascaris lumbricoides

Ascaris lumbricoides a Nematode.

1. Ascarislumbricoides
DR ARUNA RANI BEHERA
DEPARTMENT OF MICROBIOLOGY

2. NEMATODES
SHAPE -ELONGATED,CYLINDRICAL,UNSEGMENTED
SEXES -DIOECIOUS / SEPARATE
HEAD -BOTH SUCKERS AND HOOKS ABSENT
WELL DEVELOPED BUCCAL CAPSULE
BODY CAVITY -PRESENT
ALIMENTARY CANAL -PRESENT AND COMPLETE

3. Classification
According to Habitat of adult worm:
A. Intestinal nematodes
B. Tissue/Somatic nematodes
C.Other nematodes

4. A. INTESTINAL NEMATODES
SMALL INTESTINE
Ascaris lumbricoides
Ancylostoma duodenale
Necator americanus
Strongyloides stercoralis
Trichinella spiralis
Capillaria phillippiensis
LARGE INTESTINE
Enterobius vermicularis
Trichuris trichura

5. B. TISSUE/SOMATIC NEMATODES
Subcutaneous tissues
Onchocercavolvulus
Loa loa
Body cavity
Mansonellaperstans
Mansonellaozzardi
Lymphatic system
Wuchereriabancrofti
Brugiamalayi
Conjunctiva-Loa loa
C.OTHERS-Dracunculousmedinensis, Angiostrongylusspp.

6. Depending on the nature of the eggs laid, the nematode
females may be:
A. Oviparous-Ascaris lumbricoides,
-Trichuris trichura,
-Ancylostoma duodenale
-Necator americanus
-Enterobius vermicularis
B. Viviparous-Trichinella spiralis
-Wuchereria bancrofti
-Brugia malayi
-Dracunculus medinensis
C. Ovo-viviparous-Strongyloides stercoralis

7. Introduction
Ascarislumbricoidesis the most common nematode of the
human.
Largest intestinal nematode parasitisingthe human.
It is commonly known as ROUND WORM.
Habitat:
The adults live in the small intestine particularly in the
jejunum(85%) and ileum(15%).

8. Morphology
Adult worm:
Freshly passed adult worms in the
stool are pink in colourand look
like earth worms.
They are elongated and rounded in
shape with tapering ends.
Mouth opens at anterior end and
possess 3 finely toothed lips, 1
dorsal and 2 ventral.
The anterior end is thinner than the
posterior end.

9. Adult male
Adult males are relatively smaller
than females.
15-30 cm in length and 3-4mm in
diameter.
Tail is curved ventrally to form a
hook-like structure with a conical
tip.
2 curved copulatory spicules
protrude from cloaca,anus along
withejaculatory duct opens into
cloaca.

10. Adult female
Females are relatively longer
and stouter than males.
25-40 cm in length and 2-6mm
in diameter.
Tail is straight and conical but
not curved.
The vulva opens at the junction
of anterior and middle third of
the body
This part of the worm is
narrower, is called vulvar waist.
Anus opens directly on ventral
surface in form of transverse slit.

11. After mating of adult worms, a
single gravid female may have
enormous egg laying capacity
and liberate about 2,00,000 eggs
per day.
Life span-about 1 year

12. Eggs
Eggs are passed out in human feces
2 types
a. Fertilized egg
b. Unfertilisedegg

13. Fertilised egg
Round or Oval in shape.
60-75 µm in length and 40-50
µm in breadth.
Bile stained and brownish in
colour
Surrounded by a thick
translucent shell with outer
albuminous coat in form of
rugosities (mammillated).

14. Fertilised egg
Some times this outer coat is
lost, such eggs are called
decorticated eggs.
Each egg contains a large
unsegmented ovum with a clear
crescentric area at each pole.
The eggs float in saturated salt
solution.

15. Embryonated egg
Freshly passed fertile eggs are
not infective to man.
They require approximately 10
to 40 days for development
into embryonated eggs.
Only embryonated eggs are
infective to humans.

16. Unfertilised egg
Elongated and larger than fertile
egg
70-100µm length X 30-50µm
breadth.
Bile stained and brown in colour
Thinner shell with irregular
coating of albumin
Contains a small atrophied ovum
Heaviest of all helminthic eggs,
hence do not float in salt
solution.

17. Mode of Infection
Infective form-Embryonated eggs
Portal of entry-Ingestion
Site of location-Small intestine
Both fertilised and unfertilised eggs are present
in faeces.

18. Lifecycle
Completed in a single host,
Manis the only host, no
intermediate host required.
Man acquires infection by
ingestion of food, water or raw
vegetables contaminated with
embryonated eggs .

19. The fertilisedeggs containing unsegmentedovum, passed in the
faecesare not infective to man.
In the moist soil larva develops inside the egg.Undergoa period
of incubation in soil to acquire infectivity .
Rhabditiformlarva is formed from unsegmentedovum &
undergo 1
st
moultingwithin shell in 10-40 days.
The egg containing rhabditiformlarva (embryonatedegg) is
infective to man.
Man acquires infection by ingestion

20. The ingested eggs hatch in
duodenum to liberate
rhabditiform
larvae(250µmX14µm,
actively motile).
Larvae penetrate the
intestinal wall, enter
lymphaticsand venules.
These larvae are carried by
the portal circulation to the
liver, where they live for 3
to 4 days, then carried to the
right heart then to lungs.

21. In the lungs the larvae increase in
length and moults twice(5
th
and
10
th
day) and becomes fourth
stage larva.
Break through capillary wall and
reach lung alveoli
From alveoli larva crawl up
bronchi & trachea & propelled
into ,pharynx and swallowed back
to the small intestine, their normal
habitat.

22. In the small intestine, on 25
th
-29
th
day of infection the fourth
stage larva moultsonce more .
The larva grows to become adult and sexually maturity occurs
in 6-10 weeks of infection.
After fertilization the gravid female begins to lay eggs which
are passed in the faeces.
Life cycle is repeated.

25. Developmental stages of
nematodes

26. Pathogenesis and Clinical
Feature
Infection of ascaris is known as Ascariasis.
Symptoms may be due to migrating larva or due to
adult worms.
The majority of infected people are asymptomatic.
In symptomatic cases produce two major clinical
syndromes:
1. Intestinal disease
2. Pulmonary disease.

27. Intestinal disease (Due to Adult
worm)
Most important clinical manifestation of ascariasis.
Severity depends upon worm load and nutritional status of the
host.
Malnutrition and growth retardation (in children)
Severe infection –intermittent colicky cramps, loss of
appetite, abdominal pain, nausea, vomiting, fever, weight loss .
Heavy infection l/t intestinal obstruction
Allergic manifestations -fever, urticaria, angioneuroticedema
and conjunctivitis occur due to release of toxic fluid (ascaron)
by the adult worm.
These worms have been vomited and passed from mouth and
nose.

29. Pulmonary disease(Due to Migrating Larva)
Pulmonary symptoms:
-l/t inflammatory and hypersensitivity reaction in lungs
-symptoms-nonproductive cough, fever, dyspnea.
-Cough and wheezing are present in newly infected
persons.
Eosinophilicpneumonia (Loeffler’ssyndrome):
-Patients develop dyspnea, blood tinged sputum
sometimes it contain larva of ascaris& charcotleydencrystals
-Transient patchy infiltrates seen on chest X-ray
May involve organs like liver, kidney
Symptoms disappear after the larva leave the lung

30. Complications
Intestinal complications: bolus of entangled worms can
cause acute pain abdomen due to small bowel obstruction.
Perforate the intestine and enter the peritoneal cavity,
respiratory tract.
Extraintestinalcomplications: Larger worms can enter and
occlude the biliary tree, causing biliary colic, cholecystitis,
pancreatitis, rarely intrahepatic abscesses.
Migrate to pharynx and can cause respiratory obstruction
or may block the Eustachian tube

31. Prognosis
Majority of the cases are successfully treated with
antihelminthics.
Rarely death may occur in children due to intestinal
obstruction.

32. Epidemiology
A.lumbricoides has a world wide distribution.
Most infections are in the developing countries.
India:
Infection has been reported through out India.
Most of the case from Kashmir ,UP, Bihar.
Infection is common in children in rural areas.

33. Diagnosis
Clinically it is difficult to diagnose ascariasis.
Laboratory diagnosis:
1. Parasitic diagnosis
2. Serodiagnosis
3. Imaging methods

34. Parasitic diagnosis
Stool examination-Definitive diagnosis is made by
demonstration of eggs(fertilized and unfertlizedeggs) in
faeces.
-Concentration of faecesnecessary in light infections.
Adult worms detection-can be demonstrated in faecesor
vomitus.
Larva detection -In pulmonary infections larvae found in
sputum/gastric aspirates /bronchial aspirates.
Other findings -Eosinophilia and charcot-leydencrystals
in sputum and stool

35. Serodiagnosis
Commonly used test are
1. Indirect haemagglutination(IHA)
2. Immunofluorescentantibody test (IFA)
3. ELISA
Sreologicaltests are useful in diagnosis of extra-
intestinal ascariasisand sero-epidemiological surveys.

36. Imaging methods
X-Ray:
Chest x-ray may show patchy infiltration during
pulmonary phase of infection.
Abdomen x-ray may show adult ascaris in intestinal
disease.
Trolley car lines
Ultrasound:
Useful in biliary ascariasis.

37. TREATMENT
Commonly used Antihelminthicsare:
1.Mebendazole-DOC(100gm BD for 3days)
2.Pyrantal pamoate:single oral dose ,safe in
pregnancy.
3. Piperzinecitrate:Drugof choice for intestinal or
biliary obstruction secondary to ascariasis.
Symptomatic treatment

38. PROPHYLAXIS
Prevention of pollution of soil:
1. Treatment of infected persons
2. Deworming of school children
3. Avoidance of use of faecesas fertilizers.
4. Use of sanitary latrines.
5.Proper disposal of human feces
Prevention of ingestion of eggs:
1. Improved personnel hygiene.
2. Avoiding eating of uncooked green vegetables,
food
preparations and fruits contaminated with faecal
eggs.