Abstract & Commentary
Synopsis: An invited article reviewing schistosomiasis in travelers describes the pertinent features of this disease as it presents in the nonimmune tourist.
Source: Corachan M. Schistosomiasis and international travel. Clin Infect Dis. 2002;35:446-450.
By Michele Barry, MD, FACP
Since the 1980s an increase in ecotourism and adventure tourism has resulted in an increasing number of imported cases of schistosomiasis. A European network of surveillance of imported diseases comprising 11 institutions reported 151 cases during a 3-year period. Specific tourist destinations such as the Dogon tribe’s region in Mali, Banfora in Burkino Faso, the Omo National Park in Ethiopia, the southern shores of Lake Malawi in Malawi, and the Volta in Ghana have been highlighted in medical publications as areas of high risk. The infection route for the local population in areas of endemicity is the same as that for the nonimmune tourist; however the clinical presentations may differ. Several species of Schistosoma are found in specific geographic localizations (see maps). S hematobium is responsible for urinary schistosomiasis; S mansoni, S japonicum, S mekongi, and S malayi are responsible for gastrointestinal and hepatosplenic schistosomiasis; and S intercalatum has lower morbidity. CNS involvement, which is uncommon, may be found in association with S japonicum, S mansoni, and S hematobium.
Disease in Travelers
Although the majority of infections go unnoticed, when asked a number of tourists recall having "swimmer’s itch" symptoms within 48 hours of contact with water. This is never described at the time of a travel clinic appointment, Corachan claims, unless probed for. Katayma fever is a more common presentation in the traveler and represents a treatment dilemma. This acute toxemic syndrome characterized by fever, eosinophilia, hepatosplenomegaly, and urticaria is felt to represent an immunologic reaction to different stages of the parasite including the schistosmula, a juvenile form, which is not sensitive to praziquantel. Treatment regimens used during the initial stages of infection (weeks 5-6 for S mansoni and S japonicum and weeks 10-12 for S hematobium), when there is clinical and epidemiological suspicion of infection and positive serology, require a different form of therapy. As all worms may not have reached the adult stage, a second treatment dose many weeks after the initial dose should be administered. If patients present with Katayama fever, Corachan recommends corticosteroids to reduce the immunologic reaction as well as a higher dose of praziquantel 20 mg/kg every 12 hrs for 3 days because of the lower serum levels of praziquantel caused by concomitant corticosteroids.
Corachan also describes 2 unique presentations of schistosomiasis described in travelers; 1) hematospermia, with lesions on the prostate and seminal vesicles visualized by transrectal ultrasound; and 2) acute pulmonary schistosomiasis with abnormal CXRs associated with S hematobium from Lake Malawi.
Emphasis on avoiding contact with contaminated water, energetic rubbing of a body with a towel, and consideration in the future of possible use of oral artemether as a chemoprophylactic in S mansoni areas were also described in this excellent review of schistosomiasis in travelers.
Both maps were reprinted with permission from: Corachan M. Schistosomiasis and international travel. Clin Infect Dis. 2002;35:446-450. Dr. Barry, Professor of Medicine, Co-Director, Tropical Medicine and International Travelers’ Clinic, Yale University School of Medicine, is Associate Editor of Travel Medicine Advisor.