Strongyloidiasis: A Ticking Time Bomb in Vietnam War Veterans

James Diaz, MD

Strongyloides stercoralis, a soil-transmitted intestinal nematode, is distributed worldwide, but thrives in the tropics and subtropics with inadequate septic and human waste disposal infrastructures. Strongyloides causes three types of human infections—the rarely described acute strongyloidiasis, the typically asymptomatic chronic strongyloidiasis, and the potentially fatal Strongyloides hyperinfection syndrome.  Over 30 years after the end of World War II, British clinicians first observed a high rate of chronic strongyloidiasis and hyperinfection syndrome in allied ex-prisoners of war (POWs) in Southeast Asia.  Vietnam War veterans were later noted to also have increased prevalence rates of chronic strongyloidiasis and hyperinfection.  As a result of the potential for hyperinfective and disseminated strongyloidiasis in U.S. veterans, especially ex-POWs, Internet search engines were queried with the key words to meet the objectives of this review to describe the epidemiology, risk factors, and clinical course of strongyloidiasis and to recommend strategies for its early diagnosis, management, and prevention.  Given the low sensitivity of traditional laboratory tests for strongyloidiasis including direct microscopy of stool specimens for larvae, parasite culture, and serological tests, the most important preventive strategies for strongyloidiasis and its potentially lethal complications should include: (1) early recognition of risk factors for strongyloidiasis, such as wartime service, ex-POW status, and prolonged rural travel in Southeast Asia; (2) empiric treatment with ivermectin based on clinical presentation and immunocompetency status, even if unsupported by screening microscopy; and (3) consideration of prophylactic ivermectin therapy, 200 µg/kg orally for one to two days, prior to initiating corticosteroid therapy, especially in high-risk and/or immunosuppressed patients who have ever lived or traveled extensively in disease-endemic countries.

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