Ascaris Lumbricoides
Taxonomy

Kingdom : Animalia
Phylum : Nematoda
Class
: Rhabditea
Order
: Ascaridida
Family : Ascarididae
Genus : Ascaris
Species : lumbricoides
Introduction
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Common name : Round worm
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Largest of intestinal nematodes .
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causative agent of ‘Ascariasis’.
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Distribution:- world wide
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Habitat:- small intestine, mainly jejunum.
Morphological forms
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Adult worms : male
female
Eggs : fertilised
unfertilised
decorticated
Rhabditiform larva .
MORPHOLOGY
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Adult worms : cylindrical in shape with
tapering ends.
Creamy white or pinkish.
Mouth of the worm is surrounded by 3 lips
(1 dorsal and 2 ventral) with minute teeth.
Life span is <1 yr.
Adult worms
Lips of ascaris
Adult male
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smaller than female .
Size : 15-30 cm in L
3-4 mm in D .
Curved tail contains a pair of ‘copulatory
spicules’ .
Adult male
Copulatory spicules
Adult female
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Size : 20-40 cm in L
2-6 mm in D .
Post. end is straight and
conical .
‘vulvar waist’
Eggs : 240,000/day .
Adult female
Egg

3 kinds : Fertilised, Unfertilised and Decorticated.
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Fertilised egg :- oval in shape
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measures 45 x 70 mc in L
35 x 50 mc in B.
Golden brown , Bile stained .
Shell is thick with mammillated albuminous outer
coat.
Contains an unsegmented ovum with clear
crescentic space at each pole .
Floats in sat. salt solution.

Unfertilised egg :- ellipsoidal in shape
measures 78 x 105 mc in L
38 x 50 mc in B .
 Brown coloured , Bile stained , Thin shelled .
 Heaviest of all helminthic eggs , hence it doesn’t
float in sat.salt solution .
 Decorticated egg :- Both fertilised and unfertilised
eggs sometimes may lack their albuminous coat
and are colourless .
Egg shell
Ovum
Albuminous
layer
Fertilised egg
Unfertilised egg
Decorticated egg
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Rhabditiform larva :
size : 250 mc in L
14 mc in D
actively motile
larvae hatch out in duodenum
penetrates the intestinal mucosa
Hatching out larva
Pathogenesis
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Source : soil , water , food contamined with eggs.
Route : ingestion
Infective form : embryonated eggs
Host : man
No intermediate and reservoir hosts .
Life cycle
Manifestations due to of migrating larva :
 Inflammatory and hypersensitvity reactions .
 Granuloma and eosinophilic infiltration.
 Eosinophilic pneumonia
Loeffler’s syndrome .
 Symptoms : fever
cough
dyspnea
urticaria .
Manifestations due to adult :
Sporiative action
:
 Mechanical action
:
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 Allergic reaction :
release of ascaron
malnutrition
growth retardation .
abdominal pain
intestinal obstruction
intestinal perforation
fever
urticaria
Angioneurotic edema
conjunctivitis
Intestinal obst. by adult worms
Peritonitis by intest. perforation
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Ectopic ascariasis : appendicitis
obst. jaundice
haemorrhagic pancreatitis
liver abscess
Ascaris in common bile duct
Adult worms in liver
Lab diagnosis
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Parasitic diagnosis :
demo . of eggs in feaces –direct microscopy
formalin ether conc.
demo . of larvae – in sputum , bronchial aspiration
demo . of adult worms – barium meal .
Sero diagnosis :
Ab’s detected by IHA , IFA .
used for diagnosis of loeffler’s syndrome .
Imaging methods : x – ray , ct scan , ultrasound
Epidemiology
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World wide distibution through out temperate and
tropical areas .
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¼th of the world population .
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40% population in africa and asia .
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Poor sanitary conditions .
Treatment
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Mebendazole
pyrantel pamoate
piperazine citrate .
Prophylaxis
 Proper disposal of human faeces
 Avoid eating raw vegetables and salads
 Periodic treatment with antihelminthics .