Adult larvae in the small intestine may cause abdominal pain and distention. Intestinal obstruction from adult worms rarely occurs. Migration of worms into the bile duct may rarely cause acute biliary obstruction. Examination of fresh stool for characteristic eggs is diagnostic. Effective control depends on adequate sanitary treatment and disposal of infected human feces.
Visceral larva migrans is a systemic nematodiasis caused by ingestion of the eggs of the dog tapeworm, Toxocara canis, or, less commonly, the cat tapeworm, Toxocara cati, or the raccoon tapeworm, Baylisascaris procyonis (see Table 123-2).These organisms also cause ocular larva migrans.
Visceral larva migrans is most common in young children with pica who have dogs or cats as pets. Ocular toxocariasis occurs in older children. The eggs of these roundworms are produced by adult worms residing in the dog and cat intestine. Ingested eggs hatch into larvae that penetrate the gastrointestinal tract and migrate to the liver, lung, eye, CNS, and heart, where they die and calcify.
Symptoms of visceral larva migrans are the result of the number of migrating worms and the associated immune response. Light infections are often asymptomatic. Symptoms include fever, cough, wheezing, and seizures. Physical findings may include hepatomegaly, crackles, rash, and lymphadenopathy. Visual symptoms may include decreased acuity, strabismus, periorbital edema, or blindness. Eye examination
Parasitoses due to other
Ingestion of raw or inadequately
Paragonimiasis Paragonimus westermani, P. Praziquantel or bithionol miyazaki, P. mexicanus, P. kellicotti,
P. uterobilateralis, P. skjabini, P. hueitungensis, P. heterotrema, P. africanus (lung flukes) may reveal granulomatous lesions near the macula or disc. Ocular larva migrans is characterized by isolated, unilateral ocular disease and no systemic findings. Larvae probably enter the anterior vitreous of the eye from a peripheral branch of the retinal artery and elicit granulomas in the posterior and peripheral poles that cause vision loss.
Eosinophilia and hypergammaglobulinemia associated with elevated isohemagglutinin levels suggest the diagnosis, which is confirmed by serology (enzyme-linked immunosorbent assay) or, less commonly, by biopsy. This is usually a self-limited illness. In severe disease, albendazole or mebendazole is used. Deworming puppies and kittens, major excreters of eggs, decreases the risk of infection.
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Pinworm is caused by Enterobius vermicularis, a nematode that is distributed worldwide. Enterobiasis affects individuals at all socioeconomic levels, especially children. Crowded living conditions predispose to infection. Humans ingest the eggs carried on hands, present in house dust or on bedclothes. The eggs hatch in the stomach, and the larvae migrate to the cecum and mature. At night the females migrate to the perianal area to lay their eggs, which are viable for 2 days.