Ancylostoma duodenale
(Hook worms)
Human hook worms Ancylostoma duodenale is widely distributed in tropical and subtropical countries.
The adult worm live in small intestine of man, mostly in jejunum.
It causes disease called Ancylostomiasis or hook worm disease.
Morphology
Adult worm; small, greyish, white or brown.
Anterior end bend slightly dorsally posterior or back appears bookworm.
Buccal capsule is provided with 6 teeth, 4 hook like on ventral surface and 2 knob like on dorsal surface.
Oral aperture open dorsally.
Sources and Mode of Transmission
Disease is transmitted through direct skin penetration by larvae found in soil.
Pathogenesis and clinical significance
At site where filariform larvae penetrate human skin, causing dermatitis.
This parasite causes hook worm disease in man characterized by anaemia.
Pathogenic effect due to migrating larvae or due to adult worms.
Infective agent; Filariform larvae
Portal of Entry; skin
From dermis when larvae migrate of subcutaneous vessel, cause creeping eruption.
Skin Infection; itching, blister, radish
Lesions in lungs;
When larva reach lung enter alvolar space, cause multiple hemorrhage and Bronchopneumonia.
Adult worms causes irritation and penetrate, intestinal mucosa.
Life cycle
Ancylostoma duodenale completes it's life cycle in single host.
Man is the only definitive host. No intermediate host is required.
Infection can occur filariform larvae found in soil, in man capable of penetrating unbroken of skin, this infective stage of parasite.
When person walks barefood on soil containing filariform larvae, they penetrate skin.
On reaching subcutaneous tissue larvae enter into lymphatics or small venules.
Then in lymphatic system and in right side of heart, larvae originate into pulmonary circulation, where they increase in size.
Larva enter alveoli of lung, from lung alveoli larvae crawl in bronchus and reach treachea.
Trachea pushes larvae in pharynx, then larvae is swallowed by pharynx, passed through esophagus and then from stomach enters into small intestine.
In small intestine, larvae undergo develop into adult worm.
They attach themselves to small intestine by their mouth parts.
Female fertilized and they start discharging egg in stool.
Rhabditiform larvae comes out from egg in soil and undergo two mouth in soil, then produce infective filariform larva and life cycle is thus repeated.
Laboratory Diagnosis
Specimen collection
Stool specimen
Microscopic examination of stool
Adult worms seen; show infection
Show characteristics; ova (egg) in stool.
Microscopic examination of stool in normal saline
Duodenal content reveals eggs or adult worms.
Treatment
Mebendazole or pyrantel pamoate are effective.
1. Filariform larva penetrates unbroken skin of man.
2. From subcutaneous tissue larvae enter lymphatic system.
3. From venous circulation larvae enter into right side of heart.
4. Then larva migrate pulmonary circulation.
5. Then larvae enter in alveoli of lung, larvae crawl up in bronchus reach trachea and larynx and then pharynx.
6. Larva swallow by pharynx and reaches stomach into small intestine.
7. Larvae develop into adult male and female worms in small intestine.
8. Female worm starts discharging egg in stool.
9. Rhabditiform larvae comes out from egg in soil.
10. Produce Infective filariform larva.
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