[1] Ifakara Hlth Res & Dev Ctr, Ifakara, Tanzania
[2] Univ Durham, Dept Biol & Biomed Sci, Durham DH1 3LE, England
[3] Swiss Trop Inst, Dept Epidemiol & Publ Hlth, CH-4002 Basel, Switzerland
[4] Univ Nairobi, Dept Zool, Nairobi, Kenya
[5] Dar es Salaam City Council, City Med Off Hlth, Dar Es Salaam, Tanzania
[6] Univ S Carolina, Dept Geog, Columbia, SC 29208 USA