Characterization of the enzootic transmission cycle of RVFV and identification and characterization of RVFV strains in south Tanzania
Rift Valley fever (RVF) is a zoonotic disease causing devastating outbreaks which large economic losses to poor African countries. RVF virus (RVFV) is transmitted by various mosquito species but also by blood or aerosols. It is crucial to understand the mechanisms driving the transmission cycles to establish effective countermeasures. In south Tanzania RVF has not been described although there exist a high seroprevalence. We hypothesize the occurrence of an endemic low level transmission cycle of low-pathogenic RVFV strains
The mosquito-borne viral disease, Rift Valley fever (RVF) occurs mainly in the third world, where outbreaks cause high mortality in livestock and humans. In southern Tanzania there is no RVF although many in the population have antibodies to RVF virus, which means that they have had an infection. Our hypothesis is that these people have been infected by a virus that does not cause serious illness. We will investigate if this is true by taking samples of animals and mosquitoes in that area. The RVF virus that we can isolate we will study in terms of how they differ from the viruses that cause severe disease
RVF antibody and virus will be analysed in ruminants, rodents and mosquitoes to characterize the local enzootic cycle. We hypothesize that low-pathogenic RVFV circulate in rodents and that these may contribute to maintain the enzootic cycle in non-epidemic periods. They may be well adapted to their vectors and vertebrate hosts without causing severe disease. These strains may contribute to enzootic maintenance of RVFV and may act as an outbreak source when transferred to new insect vectors or vertebrates. Properties of isolated RVFV strains will be compared to highly pathogenic strains and their ability to suppress induction of the innate immune defence will be monitored. The differences in mechanismsm of pathogenesis of endemic and epidemic RVFV strains will be analysed.