Retrospective study on antibody response to vaccination of the African buffalo (Syncerus caffer) and roan antelope (Hippotragus equinus) with Clone 13 Rift Valley fever virus vaccine

Abstract

Rift Valley fever (RVF) is a disease of ruminants in Africa, Madagascar and the Middle East, affecting primarily domestic, but also many wild species. The disease can be peracute to acute and is characterised by a necrotic hepatitis and a generalised haemorrhagic syndrome. The disease is caused by a mosquito-borne virus of the Phenuiviridae family. Outbreaks occur after heavy rains, which favour the breeding of the mosquito vectors. The disease is a zoonosis and humans become infected by bites from infected mosquitoes or contact with tissue from infected animals. The first records of RVF in southern Africa date back to 1950 when a large epidemic occurred in South Africa and there have been many outbreaks since, some major, with the most recent major outbreak in SA in 2010. During the 2010 outbreak multiple indigenous wildlife species were affected, including springbok (Antidorcas marsupialis), blesbok (Damaliscus pygargus phillipsi), bontebok (D. pygargus pygargus), waterbuck (Kobus ellipsiprymnus), African buffalo (Syncerus caffer), sable (Hippotragus niger), kudu (Tragelaphus strepsiceros), nyala (Tragelaphus angasii) and gemsbok (Oryx gazella). Even though no cases have been recorded in roan (Hippotragus equinus) antelope to date, the fact that such a wide array of wildlife was affected, and taking into account the close phylogenetic relationship between sable and roan antelope, it is reasonable to assume that roan will also be susceptible to RVF. Many control methods are aimed at vector control, but since the epidemiology of the disease is still poorly understood, this has limited value. Vaccination thus provides the best means of disease prevention and RVFV Clone 13 vaccine is a new vaccine proven to be effective and safe in domestic animals. It has not yet been scientifically tested in wildlife. To date there is no published research on the use of RVF vaccine in wildlife, nor are there any recommended vaccine protocols for wildlife. Many of these species are valuable in conservation and financial terms, and hence the need for this research. The purpose of the research was: To determine whether Clone 13 RVFV vaccine is effective in creating a humoral immune response in the African savannah buffalo and roan antelope. To determine if there are any obvious clinical side effects, such as general malaise or abortion due to vaccination. The World Organisation for Animal Health (OIE) lists both the enzyme linked immunosorbent assay (ELISA) and serum neutralization test (SNT) as recommended methods for detecting an immune response in populations considered free from disease, as well as post-vaccination to detect an immune response. As reported previously, the ELISA and SNT have been used to detect antibodies against RVFV in serum of a variety of animal species.