Cow with calf


Prevention & control of Rift Valley Fever South Africa

Rift Valley fever (RVF) is a mosquito-borne viral disease that affects humans, sheep, cattle, goat, buffalo, camels as well as various wildlife species. Mortality in adult sheep and cattle is estimated at 20% and 10%, respectively, whereas in unborn and infant sheep, mortality is considerably higher, approaching 100%.

RVFV infection in humans can remain asymptomatic or manifest as a mild illness. A small percentage of individuals however develop more serious symptoms including retinal damage, hepatic disease with hemorrhagic fever or encephalitis. The mortality rate among severe cases varies from 4-40%. The causative agent, Rift Valley fever virus (RVFV), belongs to the Phlebovirus genus of the family Bunyaviridae. In South Africa, RVF outbreaks have occurred with increasing frequency, size and severity. The threat of future outbreaks of RVF in South Africa persists. Furthermore, mosquitoes that are potentially capable of transmitting RVFV are not confined to Africa, explaining the fear for epidemics outside this continent. Also in The Netherlands, several mosquito species are present that can potentially transmit RVFV to both humans and livestock. This BOCI project has supported the development of a veterinary vaccine and continues to support registration trials of the vaccine in South Africa. The main focus of this year’s project was to improve the gold-standard diagnostic test used for the detection of RVFV infections. We successfully developed and validated this novel test, which is based on virus neutralization, and demonstrated at least a 10-fold improvement in sensitivity. This assay will greatly facilitate the monitoring, and thereby the control, of RVFV infections in the field.