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Chapter: Medical Microbiology: An Introduction to Infectious Diseases: Intestinal Nematodes

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Strongyloidiasis : Clinical Aspects

Patients with strongyloidiasis do not generally give a history of “ground itch.” They do, however, manifest the pulmonary disease seen in both ascariasis and, less often, in hook-worm infection.

STRONGYLOIDIASIS : CLINICAL ASPECTS

Patients with strongyloidiasis do not generally give a history of “ground itch.” They do, however, manifest the pulmonary disease seen in both ascariasis and, less often, in hook-worm infection. The intestinal infection itself is usually asymptomatic. With heavy worm loads, however, the patient may complain of epigastric pain and tenderness, often aggra-vated by intake of food. In fact, peptic ulcer-like pain associated with peripheral eosinophilia strongly suggests the diagnosis of strongyloidiasis. With widespread involve-ment of the intestinal mucosa, vomiting, diarrhea, paralytic ileus, and malabsorption may be seen.

External autoinfection produces transient, raised, red, serpiginous lesions over the buttocks and lower back that reflect larval invasion of the perianal area. If the patient is not treated, these lesions may recur at irregular intervals over a period of decades; they are particularly common after recovery from a febrile illness. Over 25% of British and American servicemen imprisoned in Southeast Asia during World War II continued to demonstrate such lesions prior to diagnosis and treatment some 40 years after exposure.

Massive hyperinfection may occur in immunosuppressed patients, especially in those receiving glucocorticoid therapy, producing severe enterocolitis and widespread dissemina-tion of the larvae to extraintestinal organs, including the heart, lungs, and central nervous system. Inexplicably, this phenomenon has been unusual in acquired immunodeficiency syndrome (AIDS) patients, even in areas where strongyloidiasis is highly endemic. The lar-vae may carry enteric bacteria with them, producing Gram-negative bacteremia and occa-sionally Gram-negative meningitis that may result in death.

DIAGNOSIS

The diagnosis is usually made by finding the rhabditiform larvae in the stool. Preferably, only fresh specimens should be examined to avoid the confusion induced by the hatching of hookworm eggs with the release of their look-alike larvae. The number of larvae passed in the stool varies from day to day, often requiring the examination of several specimens before the diagnosis of strongyloidiasis can be made. When absent from the stool, larvae may sometimes be found in duodenal aspirates or jejunal biopsy specimens. If the pulmonary system is involved, the sputum should be examined for the presence of larvae. Agar plate culture methods may recover organisms that go undetected by microscopic examination. Enzyme-linked immunosorbent assays for antibodies to excretory – secretory or somatic antigens are now available in reference laboratories.

TREATMENT AND PREVENTION

All infected patients should be treated to prevent the buildup of the worm burden by au- toinfection and the serious consequences of hyperinfection. The drugs of choice are iver- mectin and thiabendazole. In hyperinfection syndromes, therapy must be extended for 1 week. The cure rate is significantly less than 100%, and stools should be checked after therapy to see if retreatment is indicated. Patients who have resided in an endemic area at some time in their lives should be examined for the presence of this parasite both before and during steroid treatment or immunosuppressive therapy. Medical personnel caring for patients with hyperinfection syndromes should wear gowns and gloves, because stool, saliva, vomitus, and body fluids may contain infectious filariform larvae.

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