The following points highlight the infections caused by intestinal helminthes: 1. Ascariasis 2. Ancylostomiasis 3. Enterobiasis 4. Trichuriasis 5. Strongyloidiasis.
1. Ascariasis:
This is infection with Ascaris lumbricoides which is the largest intestinal nematode, parasitising man. It has a world-wide distribution being specially prevalent in the tropics like China, India and South-East Asia. The disease is common in persons with unhygienic habits.
The adult worm resembles an ordinary earthworm. The male is about 15- 25 cm. in length with the tail end curved ventrally like a pointed hook. The female worm is neither curved nor pointed.
Life-Cycle:
Man is the only definitive host. The worms reside in the small intestines. A fertilised female liberates eggs which escape in faeces and undergo development in faeces and further development in soil so as to infect food, drink or raw vegetables. Now the man ingests eggs containing larvae which bore through intestinal mucosa and are carried by portal circulation to liver and via right heart to lungs.
Therefrom larvae break out of pulmonary capillaries and enter lung alveoli to grow and eventually crawl up the bronchi and trachea into the larynx and pharynx to be swallowed again to localise in the upper part of the small intestine to develop into adult worms.
Clinical Features:
Pain abdomen, abdominal distension, anorexia, malnutrition, urticaria, and diarrhoea. Occasionally intestinal obstruction is encountered. Migration of larvae may cause ascaris pneumonia (Loeffler’s syndrome), hepatomegaly or encephalopathy.
Diagnosis:
Discovery of the adult worms or the eggs in the faeces.
Treatment:
(i) Piperazine salts give a maximum of 3-4 gm, as single dose in adults for two days. For children dose is 75 mg/kg.
(ii) L-tetramisole 5 mg/kg given in a single dose.
(iii) Mebendazole tablet given in a dosage of 100 mg, twice daily for 3 days.
2. Ancylostomiasis:
This is infection with ancylostoma doudenale. It occurs in temperate climates in Europe, in the Middle East, North Africa and in certain areas of the Far East. The adult worm’s measure 1 cm. in length, the female is a little larger than the male; the body is slightly curved and tapered at both ends.
Life-Cycle:
Man is the only definitive host. Eggs escape in faeces and develop in soil so as to cause hatching out of rhabditiform larvae and filariform larvae, the latter being infective enter the body penetrating the skin and pass through the lymphvascular system into the venous circulation to be carried to the right heart into the pulmonary capillaries. Therefrom through the alveolar spaces they migrate on to the bronchi trachea, larynx and crawl over the epiglottis to be swallowed to develop into adult worms in the intestine.
Clinical Features:
Pain abdomen, malnutrition, progressive anaemia, anorexia, oedema and diarrhoea alternating with constipation. Larvae can cause ground itch at their site of penetration.
Diagnosis:
Discovery of the eggs in the faeces.
Treatment:
(i) Bephenium hydroxynaphthoate—5 gm daily to be taken for 3 consecutive days in stomach. For children dosage in 20 mg/kg. It is the drug of choice and is also useful for mixed HW & RW infestations.
3. Enterobiasis:
This is the infection with Enterobius Vermicularis. It has world-wide distribution and is not influenced by climate. The worm is small thread-like. The males have coiled tails and are about half the size of the females which may reach about 1 cm. in length.
Life-Cycle:
The gravid femaleworms creep out of anus and lay eggs which adhere to the skin or the clothing and are transferred therefrom to fingers and towels. The embryonated eggs rapidly develop and become infective when swallowed, larvae escape in the intestine and male and female worms develop.
Clinical Features:
Itching round the anus and perineum, nocturnal enuresis, rarely appendicitis, pruritus vulvae may occur in young girls.
Diagnosis:
Demonstration of the worms or of the eggs in the stool or in the scrappings from the perianal skin.
Treatment:
(i) Piperazine 50-75 mg/kg daily (maximum 2 g) orally for 7 days.
(ii) L-tetramisole 2.5 mg/kg in a single dose.
(iii) Mebendazole—as in ascariasis.
(iv) Other effective drugs are viprynium embonate and pyrantel embonate.
4. Trichuriasis:
This is infection with trichuris trichura. It is especially found in the tropics.
The worm measures about 5 cm. in length. The female is larger than the male. The anterior part thread-like, the posterior thicker and cylindrical.
Life-Cycle:
The eggs come out of the human host with faeces and develop in soil to produce embryonated eggs which when swallowed larvae are liberated and each larva becomes an adult worm.
Clinical Features:
Abdominal pain, dysentery often with bloodstained stool occurs in heavy infection. Appendicitis may also develop if vermiform appendix is infected.
Diagnosis:
Discovery of the characteristic eggs by a microscopical examination of a saline emulsion of the faeces.
Treatment:
(i) Thiabendazole—50 mg/kg orally for 2 days.
(ii) Mebendazole—as in ascaris.
5. Strongyloidiasis:
This is infection with strongyloides stercoralis. It occurs in many parts of the world, particularly in the East, South America and Africa. These worms are hardly visible to the naked eye.
Life-Cycle:
The eggs hatch in the human host and larvae are passed in the faeces which usually develop into free living adults and this cycle may be repeated, ultimately, however, filariform larvae are formed which penetrate the human skin to reach via heart, the pulmonary vessels and alveoli and then the intestine.
Clinical Features:
Abdominal discomfort, pain abdomen, diarrhoea, urticaria.
Diagnosis:
Demonstration of the typical rhabditiform larvae in freshly passed stool.
Treatment:
(i) Thiabendazole 25 mg/kg twice daily for 3 days.