[Rift Valley Fever: veterinary aspects and impact for human health]

Rift Valley fever (RVF) is an arboviral zoonosis affecting a wide range of animal species as well as humans. Clinical incidence in domestic ruminants is high with infection causing abortions in pregnant animals and high mortality rates in newborns. In humans, clinical disease appears in about 50% of infected individuals. Human illness is characterized by dengue-like symptoms with severe complications including encephalitis, retinitis, hemorrhagic fever and death occurring in 1 to 3% of cases. During epidemic outbreaks, transmission between animals or from animals to humans is mainly by direct contact with infected biological material. Under these conditions, mosquito transmission probably plays a greater role in maintaining the enzootic cycle and initiating epizootic and epidemic outbreaks during the periods of heavy rainfall. The last epidemic outbreak of RVF in Kenya, Somalia, Tanzania and Sudan in 2006-2007 killed more than 4,000 ruminants and 600 humans. After confirmed diagnosis of one human case in 2007 in Comoros, an epidemiological survey was carried out in ruminant livestock in Mayotte. Results indicated that the RVF virus has been circulating on the island since 2005. In addition, serum samples collected from patients presenting dengue-like symptoms confirmed approximately 10 cases of human infection in 2007-2008. These results suggest low-level circulation of the RVF virus in Mayotte with weak impact on human and animal health. An assessment of future risk for the island is presented.