Chapter 3Infectious Diseases Related To Travel

LeAnne M. Fox

INFECTIOUS AGENT

Strongyloidiasis is caused by an intestinal nematode, Strongyloides stercoralis.

MODE OF TRANSMISSION

Infection occurs when filariform larvae found in infected soil penetrate human skin. Person-to-person transmission is rare but has been documented.

EPIDEMIOLOGY

Strongyloides is endemic in the tropics and subtropics, and in limited foci in the southeastern United States, Europe, Australia, and Japan. Estimates of global prevalence vary between 3 million and 100 million. Most infections seen in the United States occur in immigrants, refugees, and military veterans who have lived in endemic areas for long periods of time. Risk for short-term travelers is very low, but infections can occur.

CLINICAL PRESENTATION

Most infections are asymptomatic. With acute infections, a localized, pruritic, erythematous papular rash can develop at the site of skin penetration, followed by pulmonary symptoms (a Löffler-like pneumonitis), diarrhea, abdominal pain, and eosinophilia. Migrating larvae in the skin can cause larva currens, a serpiginous urticarial rash.

Immunocompromised people, especially those receiving systemic corticosteroids or patients with human T-cell lymphotropic virus type 1 infection, are at risk for hyperinfection or disseminated disease, characterized by abdominal pain, diffuse pulmonary infiltrates, and septicemia or meningitis from enteric gram-negative bacilli. The death rate from untreated disseminated strongyloidiasis is high. Unexplained eosinophilia may be a presenting sign of strongyloidiasis.

DIAGNOSIS

Diagnosis is made by finding rhabditiform larvae on microscopic examination of the stool, either directly or by culture on agar plates. Repeated stool examinations or examination of duodenal contents may be necessary, given the low sensitivity of a single stool examination. Hyperinfection and disseminated strongyloidiasis are readily diagnosed by examining stool, sputum, cerebrospinal fluid, and other body fluids and tissues, which typically contain high numbers of larvae. Serologic testing using an immunoassay is useful and available through the National Institutes of Health and CDC’s Division of Parasitic Diseases and Malaria (www.dpd.cdc.gov/dpdx).

TREATMENT

Ivermectin (200 µg/kg orally for 2 days) is the treatment of choice for both chronic infection and disseminated disease with hyperinfection. Albendazole is an alternative agent, although associated with slightly lower cure rates. Prolonged or repeated treatment may be necessary in patients with hyperinfection and disseminated strongyloidiasis, and relapse can occur.

PREVENTIVE MEASURES FOR TRAVELERS

No vaccine is available. No drugs for preventing infection are available. Protective measures include wearing shoes when walking in areas where humans may have defecated.

BIBLIOGRAPHY

1. Abramowicz M. Drugs for Parasitic Infections. New Rochelle (NY): The Medical Letter, Inc; 2007.
2. Adedayo O, Grell G, Bellot P. Hyperinfective strongyloidiasis in the medical ward: review of 27 cases in 5 years. South Med J. 2002 Jul;95(7): 711–6.
3. Arthur RP, Shelley WB. Larva currens; a distinctive variant of cutaneous larva migrans due to Strongyloides stercoralis. AMA Arch Derm. 1958 Aug;78(2):186–90.
4. Cappello M, Hotez PJ. Disseminated strongyloidiasis. Semin Neurol. 1993 Jun;13(2):169–74.
5. Genta RM, Weesner R, Douce RW, Huitger-O’Connor T, Walzer PD. Strongyloidiasis in US veterans of the Vietnam and other wars. JAMA. 1987 Jul 3;258(1):49–52.
6. Grove DI. Human strongyloidiasis. Adv Parasitol. 1996;38:251–309.
7. Gyorkos TW, Genta RM, Viens P, MacLean JD. Seroepidemiology of Strongyloides infection in the Southeast Asian refugee population in Canada. Am J Epidemiol. 1990 Aug;132(2):257–64.
8. Keiser PB, Nutman TB. Strongyloides stercoralis in the immunocompromised population. Clin Microbiol Rev. 2004 Jan;17(1):208–17.
9. Siddiqui AA, Berk SL. Diagnosis of Strongyloides stercoralis infection. Clin Infect Dis. 2001 Oct 1;33(7):1040–7.
10. Zaha O, Hirata T, Kinjo F, Saito A. Strongyloidiasis—progress in diagnosis and treatment. Intern Med. 2000 Sep;39(9):695–700.