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Acute Schistosomiasis in U.S. Travelers Returning from Africa

In December 1988 and May 1989, CDC was notified that members of two groups of travelers who had recently returned to the United States from Botswana and Cote d'Ivoire, respectively, had experienced illnesses characterized by an influenza-like syndrome and eosinophilia. Subsequent investigations documented the occurrence of acute schistosomiasis in each group.

Botswana. From September 14 to October 2, 1988, a group of 16 persons visited the Okavango Delta region of Botswana. Twelve of 13 travelers who responded to mailed questionnaires reported contact with fresh water (e.g., wading, swimming, bathing, washing, and boating) while in this region. None reported recent water contact in other geographic areas in which schistosomiasis was endemic. Within 5 weeks of the expedition, 11 persons had onset of symptoms that included fatigue, fever, sweats, chills, headache, and gastrointestinal discomfort. These symptoms lasted 1-30 days (mean: 8 days) and recurred in five persons 11-20 days (mean: 15 days) after the initial episode.

Complete blood counts done for six persons found peripheral eosinophilia (range: 10%-57%; normal: 0-4%). Of fecal specimens from 11 persons, nine contained small numbers of Schistosoma eggs having characteristics of both S. mansoni and S. rod haini. Urine samples from three persons were negative for ova of S. haematobium. Fifteen travelers submitted serum specimens, and all were positive for antibodies to Schistosoma sp. The one member of the group who did not submit a serum sample reportedly had S. mansoni ova in a stool specimen.

Persons with positive fecal and/or serologic specimens were treated with a single oral dose of praziquantel (40 mg/kg). All symptoms resolved after treatment, and no serious adverse reactions to therapy were reported. Twelve of the 13 travelers who completed questionnaires were aware of the risks of acquiring malaria and diarrheal illness in this region; seven reported having been advised about the risks for schistosomiasis.

Cote d'Ivoire. From March 1 to April 15, 1989, eight persons traveled to a remote rural area of western Cote d'Ivoire. During their visit, seven members of this group were briefly in contact (bathing, wading, and/or swimming) with fresh river water. None had recently traveled to other areas in which schistosomiasis was endemic.

All seven persons reported transient pruritus immediately after their exposures. Two to 4 weeks later, six of these seven persons developed symptoms including fever, chills, fatigue, headache, and gastrointestinal discomfort. Initial symptoms lasted 2-25 days (mean: 12 days) but recurred within 1-4 weeks in all six patients. Four persons required hospitalization, and five were treated presumptively for malaria. Eosinophilia (range: 15%-48%) occurred in all patients. Fecal examinations in four persons detected ova of S. mansoni; egg counts were low and ranged from 16 to 24 eggs per gram of feces. For all seven persons, urine examinations were negative for Schistosoma ova. For six persons, serum specimens were positive for antibodies to Schistosoma sp. All six were successfully treated with praziquantel.

Each of these seven travelers had received pretravel health advice and were taking malaria prophylaxis. Four were advised about methods for avoiding diarrheal illness; one was cautioned regarding the potential risks for schistosomiasis. Reported by: TW Cummings, MD, San Diego; MN Gropper, MD, Univ of California, San Fran cisco; JE Galpin, MD, Tarzana; KH Acree, MD, California Dept of Health Svcs. RS Gutin, MD, L Szczukowski, MD, Denver; RE Hoffman, MD, State Epidemiologist, Colorado Dept of Health. M Kohan, MD, Coral Springs; CL MacLeod, MD, Miami, Florida. KE Droulard, MD, Dept of Pathology, Mercy Medical Center, Nampa; FR Dixon, MD, State Epidemiologist, Div of Health, Idaho Dept of Health and Welfare. BL Graham, MD, Jackson, Mississippi. S Wilson, MD, Dept of Pathology, San Juan Regional Medical Center, Farmington; CM Sewell, DrPH, State Epidemiologist, New Mexico Health and Environment Dept. S Vogh, MD, Copenhagen, Denmark. Parasitic Diseases Br, Div of Parasitic Diseases, Center for Infectious Diseases; Div of Field Svcs, Epidemiology Program Office, CDC.

Editorial Note

Editorial Note: The occurrence of these two outbreaks within a 9-month period and the high infection rates emphasize that schistosomiasis poses a continuing hazard for persons traveling in areas in which the disease is endemic. Reports of at least five similar outbreaks among U.S. and European tourists since 1975 have indicated similarly high infection rates (range: 55%-100%; mean: 77%). In these five outbreaks, symptoms of acute schistosomiasis (Katayama syndrome) were reported to occur in 40%-93% (mean: 76%) of those infected (1-6). These symptoms are thought to result from an immunologic response to the maturation of adult worms and subsequent egg deposition in the vasculature surrounding the intestines and bladder (7) (Figure 1). Although the clinical outcome in travelers is usually benign, hospitalization is sometimes necessary, and manifestations can be severe. For example, in 1984, two U.S. students developed transverse myelitis and paraplegia after acquiring infection in Kenya (4).

Early manifestations of acute schistosomiasis are often nonspecific and may easily be misdiagnosed. The diagnosis should be considered when eosinophilia is associated with fever, fatigue, headache, and/or gastrointestinal distress in persons who have been exposed to fresh water in areas in which schistosomiasis is endemic. Early diagnosis and treatment based on clinical, epidemiologic, and serologic criteria may be important in preventing serious sequelae (e.g., transverse myelitis) of acute infection. Screening stool and urine specimens for ova and parasites is the traditional method of diagnosis, but signs and symptoms of acute infection can occur before detectable egg excretion (8). Sensitive and specific serologic tests have recently been developed that can help establish the diagnosis before substantial egg deposition or excretion (9). Single-day therapy with praziquantel (40-60 mg/kg) is effective against all species of schistosomes (10). Although side effects to treatment have been reported, they are generally mild and transient (7).

Because there is no practical way to distinguish infected from noninfected water, all fresh water in schistosomiasis-endemic areas should be considered suspect. If fresh water contact is unavoidable, bathing water should be heated to 50 C (122 F) for 5 minutes or treated with iodine or chlorine in a manner similar to that used for treating drinking water. In addition, water can be strained with paper filters or allowed to stand for 3 days before use. Vigorous towel drying and application of rubbing alcohol to exposed skin immediately after contact with untreated water also may help reduce cercarial penetration and subsequent infection (3,4).

Schistosomiasis is endemic in 74 countries in Africa, South America, the Caribbean, and Asia (10). Because travel to these areas is becoming increasingly popular, health-care providers should be aware of the clinical manifestations, methods for diagnosis, and appropriate treatment of this disease. In addition, health and travel professionals should provide more intensive preventive counseling to persons planning travel to areas endemic for schistosomiasis.


  1. Zuidema PJ. The Katayama syndrome: an outbreak in Dutch

tourists to the Omo National Park, Ethiopia. Trop Geogr Med 1981;33:30-5.

2. CDC. Cercarial dermatitis among bathers in California; Katayama syndrome among travelers in Ethiopia. MMWR 1982;31:435-8.

3. Istre GR, Fontaine RE, Tarr J, Hopkins RS. Acute schistosomiasis among Americans rafting the Omo River, Ethiopia. JAMA 1984;251:508-10.

4. CDC. Acute schistosomiasis with transverse myelitis in American students returning from Kenya. MMWR 1984;33:445-7.

5. Chapman PJC, Wilkinson PR, Davidson RN. Acute schistosomiasis (Katayama fever) among British air crew. Br Med J 1988;297:1101.

6. Stuiver PC. Acute schistosomiasis in Schistosoma haematobium infection. In: Steffen R, Lobel HO, Haworth J, Bradley DJ, eds. Travel medicine. Berlin: Springer-Verlag, 1989:381-3.

7. Nash TE, Cheever AW, Otteson EA, Cook JA. Schistosome infection in humans: perspectives and recent findings. Ann Intern Med 1982;97:740-54.

8. Hiatt RA, Sotomayor ZR, Sanchez G, Zambrana M, Knight WB. Factors in the pathogenesis of acute schistosomiasis mansoni. J Infect Dis 1979;139:659-66.

9. Hancock K, Tsang VCW. Development and optimization of the FAST-ELISA for detecting antibodies to Schistosoma mansoni. J Immunol 1986;92:167-86. 10. World Health Organization. The control of schistosomiasis. Geneva: World Health Organization, 1985. (WHO technical report series, no. 728).

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