Page 89 - Medical Parasitology_ A Textbook ( PDFDrive )

82 10 Nematodes: Roundworms

worm. It is not a blood feeder like hookworm. In heavy and chronic infections, iron
deficiency anaemia may develop. Mechanical blockage of the appendix lumen by
adult worms may cause acute appendicitis. The worm may be found even up to the
rectum in heavy infection. In Trichuris dysentery syndrome (TDS), there is heavy
colonic infection which causes mucoid diarrhoea, dysentery, rectal prolapse, iron
deficiency anaemia and finger clubbing. Children with severe T. trichiura infection
have growth retardation, impaired mental development and cognitive function.

Diagnosis
1. Microscopic examination
Detection of the characteristic barrel-shaped eggs in stools.
2. Sigmoidoscopy
Sigmoidoscopy is useful in severe infection as worms are found in the
rectum.

Treatment
Mebendazole (100 mg orally twice/day for 3 days), albendazole (400 mg orally for
3 days), or ivermectin (200 μg/kg/day orally for 3 days).

Prevention and Control
1. Proper faecal disposal
2. Wash fruits and vegetables before consumption
3. Personal hygiene
4. Treatment of infected persons

Ascaris lumbricoides

Common name Common roundworm

Distribution
It is distributed worldwide mainly in the tropics and subtropics.
Habitat
Adult worms live in the lumen of the small intestine.

Morphology
The adult Ascaris worms are large and cylindrical, with tapering ends (Fig. 10.3a).
The adult male worm measures 15–30 cm in length. Its posterior end is curved with
2 copulatory spicules. The female worm measures 20–40 cm in length. Its posterior
extremity is straight and conical. The vulva is situated mid-ventrally, near the junc-
tion of the anterior and middle thirds of the body. A groove (vulvar waist) is seen
surrounding the worm at the vulvar opening and this is to facilitate mating.