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Cercarial Transformation and in vitro Cultivation of Schistosoma mansoni Schistosomules
Published on: August 16, 2011
Schistosomiasis in Lake Malawi
M S Cetron1, L Chitsulo, J J Sullivan
1Division of Parasitic Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA.
Lancet (London, England)
|November 9, 1996
Summary
Schistosomiasis transmission is occurring in Lake Malawi, a previously unrecognized site. Recreational water contact, particularly at Cape Maclear, significantly increases the risk of Schistosoma haematobium infection for expatriates and tourists.
Area of Science:
- Tropical Medicine
- Parasitology
- Epidemiology
Background:
- Central nervous system schistosomiasis cases were reported in 1992 among Peace Corps volunteers at Cape Maclear, Lake Malawi.
- This occurred despite Lake Malawi being considered a schistosomiasis-free area.
- This prompted an investigation into transmission potential and infection risk in Lake Malawi.
Purpose of the Study:
- To determine the transmission potential of schistosomiasis in Lake Malawi.
- To assess the risk of acquiring schistosomiasis for expatriates and visitors.
- To identify specific locations associated with increased risk.
Main Methods:
- A cross-sectional survey of expatriates and visitors in Malawi was conducted in 1993.
- Participants provided blood samples for Schistosoma haematobium and Schistosoma mansoni seroprevalence testing using ELISA and immunoblot.
- A survey for snail vectors was performed along the southwestern shore of Lake Malawi.
Main Results:
- Of 955 participants, 303 (32%) showed serological evidence of schistosome infection.
- Seroprevalence was 32% (141/440) among those with freshwater exposure limited to Lake Malawi.
- Infection risk increased with freshwater exposure frequency at Lake Malawi resorts, with Cape Maclear showing the highest association (OR 2.9).
- Infected Bulinus globosus snails, the vector for S. haematobium, were found at Cape Maclear and other sites.
Conclusions:
- Schistosoma haematobium infection is highly prevalent among expatriates and tourists in Malawi.
- Recreational water contact at popular Lake Malawi resorts is the likely source of infection.
- Lake Malawi represents a significant, previously under-recognized site of schistosomiasis transmission.
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