JOURNAL OF THE LOUISIANA STATE MEDICAL SOCIETY
Strongyloidiasis: A Ticking Time Bomb in VietnamWar 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. VietnamWar 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 screeningmicroscopy; and (3) consideration of prophylactic ivermectin therapy, 200 µg/ kgorally for one to twodays, prior to initiating corticosteroid therapy, especially inhigh-risk and/or immunosuppressed patients who have ever lived or traveled extensively in disease-endemic countries.
INTRODUCTION
Strongyloides stercoralis , a soil-transmitted intestinal nematode, is distributedworldwide, but thrives in the tropics and subtropics with inadequate septic and waste disposal infrastructures including the Southeast United States (U.S.). Strongyloides has a dual life cycle with an asexual life cycle causing infections in man and a free-living sexual life cycle in nature. Strongyloides causes three types of human infections. Acute strongyloidiasis is rarely described and may range from asymptomatic infection to a combination of high fever, fatigue, urticarial rash, and dry cough. Chronic strongyloidiasis is also mildly symptomatic and results from recurrent autoinfection by larvae that penetrate the duodenal mucosa internally or the perianal skin externally causing transient heartburn and pruritus ani. Lastly, the Strongyloides hyperinfection syndrome occurs in patients with chronic strongyloidiasis who have received corticosteroids or are immunosuppressed by co-morbidities both of which limit the host’s protective immune response to parasitic infection. 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) who had acquired infections during imprisonment in Southeast Asia. 1-4 Vietnam War veterans also have increased prevalence
rates of chronic strongyloidiasis and hyperinfection. 5,6 As our more recent veterans age and are treated for common chronic comorbidities, such as asthma and chronic obstructive pulmonary disease (COPD) with corticosteroids, they too will be increasingly predisposed to hyperinfection and disseminated strongyloidiasis. 5, 6 As a result of the potential for hyperinfective and disseminated strongyloidiasis in U.S. veterans, especially ex-POWs, the objectives of this review were to describe the epidemiology, risk factors, and clinical course of Strongyloides stercoralis infections and to recommend strategies for the early diagnosis, management, prevention and control of strongyloidiasis and its potentially fatal complications.
METHODS
To meet the objectives of this review, Internet search engines including PubMed, Medline, Ovid, Google®, Google Scholar® and Cochrane were queried with the key words as medical subject headings in order to identify peer-reviewed scientific articles on strongyloidiasis and its risk factors, laboratory diagnosis, management, and prevention during the search period, 1970-present. The key words included Strongyloidiasis,
18 J La State Med Soc VOL 170 JANUARY/FEBRUARY 2018
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