The epidemiology and socio-economic impact of rift valley fever epidemics in Tanzania: a review

Rift Valley Fever (RVF) is an acute, mosquito-borne viral disease that has a significant global threat to humans and livestock. This review was conducted to provide comprehensive update on Rift Valley Fever (RVF) in Tanzania, with particular attention devoted to trend of occurrence, epidemiological factors, socioeconomic impact and measures which were applied to its control. Information presented in this paper was obtained through extensive literature review. RVF occurred for the first time in Tanzania in 1930. This was followed by periodic epidemics of 10-20 years i.e. 1947, 1957, 1977, 1997 and 2007. During the latest disease outbreak in 2007 (the expanded to cover wider area of the country) 52.4% (n=21) of regions in Tanzania mainland were affected and majority (72.7%, n=11) of the regions had concurrent infections in human and animals. Phylogenetic comparison of nucleotide and amimo acid sequences revealed different virus strains between Kenya and Tanzania. Epidemiological factors that were considered responsible for the previous RVF epidemics in Tanzania included farming systems, climatic factors, vector activities and presence of large population of ruminant species, animal movements and food consumption habits. The disease caused serious effects on rural people’s food security and household nutrition and on direct and indirect losses to livestock producers in the country. Psycho-social distress that communities went through was enormous, which involved the thinking about the loss of their family members and/or relatives, their livestock and crop production. Socially, the status of most livestock producers was eroded in their communities. Steps taken to combat epidemics included restriction of animal movements, ban of the slaughter of domestic ruminants and vaccination of livestock and health education.