Wesselsbron virus – Mosquito-borne disease

Wesselsbron virus is transmitted mostly by Aedes mosquitoes found in wetlands and floodwater areas.

It is similar to Rift Valley fever, although not as deadly. Laboratory tests are often needed to confirm it.

“Wesselsbron virus is widespread throughout sub-Saharan Africa, causing fever in sheep and cattle. It is associated with hepatitis, haemorrhages, abortion and mortality in newborn lambs. It has been found in encephalitis cases in horses, ostriches and humans in South Africa,” says Prof Marietjie Venter.

Only a live vaccine is available, which can be used in conjunction with the live Rift Valley vaccine, but not in pregnant animals. Preventative inoculation with the vaccine is only a partial control measure, as viruses’ characteristics change. Reducing or eradicating insect vectors as a preventative measure must be a priority, and includes the following:

  • Regular spraying of stock with insecticidal solutions;
  • Paying attention to body parts not covered with wool;
  • Regularly cleaning and treating of drinking troughs and reservoirs to destroy mosquito breeding habitats;
  • Moving sheep away from river and vlei camps where mosquitoes breed, to higher ground.

Sources: AO de Kock (undated). ‘Rift Valley Fever and Wesselsbron Information Sheet’, Elsenburg/Vredendal Veterinary Services, www.elsenburg.com

CWA Belonje. ‘Wesselsbron Virus Disease and Middelburg Sheep Disease (Part 2)’. Merino Breeders’ Journal 19.