Ascaris Lumbricoides

Taxonomy

 Kingdom : Animalia Phylum : Nematoda Class : Rhabditea Order : Ascaridida Family : Ascarididae Genus : Ascaris Species : lumbricoides

Introduction

 Common name :

Round worm

 Largest of intestinal nematodes .

 causative agent of ‘

Ascariasis

’.  Distribution:- world wide  Habitat:- small intestine, mainly jejunum.

Morphological forms

   Adult worms : male female Eggs : fertilised unfertilised decorticated Rhabditiform larva .

MORPHOLOGY

   

Adult worms

tapering ends.

: cylindrical in shape with 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

   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

    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

.

    

Fertilised egg

:- oval in shape 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 .

Fertilised egg Egg shell Ovum Albuminous layer Unfertilised egg

Decorticated egg

 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

     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 Allergic reaction

: : malnutrition growth retardation .

: abdominal pain intestinal obstruction intestinal perforation release of

ascaron

fever urticaria Angioneurotic edema conjunctivitis

Intestinal obst. by adult worms Peritonitis by intest. perforation



Ectopic ascariasis

: appendicitis obst. jaundice haemorrhagic pancreatitis liver abscess

Ascaris in common bile duct Adult worms in liver

Lab diagnosis

  

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

 World wide distibution through out temperate and tropical areas .

 ¼th of the world population .

 40 % population in africa and asia .

 Poor sanitary conditions .

Treatment

 Mebendazole pyrantel pamoate piperazine citrate .

Prophylaxis

   Proper disposal of human faeces Avoid eating raw vegetables and salads Periodic treatment with antihelminthics .