Rift Valley Fever Threat Looms Over South African Livestock After Heavy Summer Rains

Heavy rainfall across large parts of South Africa has created ideal conditions for the transmission of Rift Valley fever (RVF), with standing water serving as breeding grounds for mosquitoes that spread the virus. This situation has raised concern among veterinary and agricultural experts, as large-scale RVF outbreaks historically occur every 10 to 15 years, with severe outbreaks recorded in 1974/75 and 2010/11. Sporadic smaller outbreaks have occurred in the intervening years, but the recent case reported in November 2025 in a sheep flock in the Northern Cape has triggered closer monitoring. Experts are warning that the current conditions may serve as an early indicator of a potential outbreak following the good summer rains. Farmers are being urged to recognize the risk and take proactive measures to protect their livestock before the situation escalates.

Vaccination remains the most effective protection against Rift Valley fever, yet many farmers do not administer it annually because major outbreaks are infrequent. According to Dan Kriek, general manager of the National Wool Growers’ Association (NWGA), a large proportion of animals currently lack immunity, creating significant vulnerability to the virus. Sheep are particularly susceptible, while goats, cattle, and even buffalo can also contract RVF. The virus poses a risk to humans, especially those handling infected or deceased animals, making preventive measures essential for both livestock and public health. Kriek emphasizes that regular and timely vaccination should become standard practice on farms, even during periods when no major outbreak is evident.

Proper vaccination requires careful selection of the correct type of vaccine, particularly for pregnant animals. Onderstepoort Biological Products (OBP) produces two vaccines: the live attenuated Smithburn strain and an inactivated “killed” vaccine. The live vaccine is not safe for pregnant animals as it can induce abortions, whereas the inactivated vaccine can be used safely but requires a booster dose a few weeks after the initial shot. Because many animals in communal farming areas are pregnant year-round, the live vaccine is often unsuitable, and the effective demand for inactivated vaccine doubles. This need for precise vaccine administration underscores the importance of planning and resource coordination to prevent large-scale infection.

The NWGA is actively collaborating with other industry bodies, including the Red Meat Producers’ Organisation and Mohair South Africa, as well as relevant authorities, to ensure rapid response capability in the event of a major outbreak. Kriek warns that if an outbreak similar to 2010/11 occurs, South Africa will require substantial quantities of inactivated vaccine to protect livestock effectively. This preparedness involves ensuring sufficient supply, timely distribution, and clear guidance to farmers on proper administration. The emphasis is on preventing the virus from spreading, protecting animal health, and maintaining the stability of livestock production across affected regions.

With the right measures, including regular vaccination, monitoring, and industry coordination, the risk of a catastrophic RVF outbreak can be mitigated. Farmers are encouraged to act now, vaccinating naïve and at-risk animals to reduce the chances of widespread infection. Early intervention and adherence to recommended protocols are critical for safeguarding both livestock and human health. As South Africa faces favorable conditions for RVF transmission, proactive action is essential to maintain food security, protect livelihoods, and prevent the devastating economic and health impacts of a major outbreak.