Pathogenesis and clinical manifestations

■ Skin lesions are observed when the larvae of Strongyloides species penetrate the skin, in particular in sensitized persons. Larvae of Strongyloides species from animals can cause "cutaneous larva migrans" (p. 602).

■ In the lungs, the migrating larvae provoke hemorrhages and inflammatory reactions that manifest clinically as pneumonic symptoms and coughing.

■ During the intestinal phase, heavy Strongyloides infections cause catar-rhal, edematous, or ulcerative forms of enteritis as well as colitis.

■ Systemic infection. A Strongyloides infection can persist in a latent state for many years due to continuous autoinfection. If immune defense is compromised, for instance by AIDS or immunosuppressive therapy, parasite reproduction can be stimulated, resulting in massive systemic infections (hy-perinfections) in which Strongyloides larvae are found in the walls of the colon and mesenteric vessels, in the bile ducts and in other organs. In such cases sexually mature female worms are also found in the lungs, and less frequently in other organs as well. A broad spectrum of symptoms is associated with systemic infection.

Diagnosis. Larvae (Fig. 10.1, p. 544) of S. stercoralis can be detected in fecal samples with the Baermann method and/or larval culture in about 6070% of infected persons (egg detection with flotation technique for S. JUelleborni). Better results can be expected if duodenal fluid is examined.

Serum antibodies are present in about 85% of immunocompetent persons with S. stercoralis larvae in their stools (Table 11.5, p. 626). In infections with other helminths, especially filariae, cross-reactions occur that can be avoided by using recombinant proteins as antigens in the ELISA.

Therapy and prevention. The main drugs used for therapy are albendazole, mebendazole, and more recently ivermectin. Preventive measures resemble those taken to prevent hookworm infections. Travelers returning from tropical countries should be thoroughly examined for Strongyloides infections before any immunosuppressive measures are initiated (e.g., for a kidney transplantation).

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Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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