[1] Univ Bern, Inst Infect Dis, Fac Med, Bern, Switzerland
[2] Univ Zurich, Inst Parasitol, Vet Fac, Zurich, Switzerland
[3] Univ Zurich, Fac Med, Zurich, Switzerland
[4] Med Univ Vienna, Inst Specif Prophylaxis & Trop Med, Med Parasitol, Vienna, Austria