“They might be inactive in cold weather but the fact is that the mosquitoes have already feasted on the blood of infected animals"
EXPERTS have warned that a “serious” Rift Valley fever outbreak could be looming for South Africa, following the death of 250 sheep on a farm outside Kimberley as a result of the virus.
Animal health company, Afrivet, has said that a recent warning issued by authorities in Kenya of a possible Rift Valley fever epidemic, has to sound a clarion call for vaccination in South Africa.
Earlier this month, six people in Kenya were reported to have died as a result of Rift Valley fever, a highly contagious disease that is transmitted to humans by close contact with contaminated animals’ blood or organs, according to the World Health Organisation.
Last month, the Department of Agriculture, Forestry and Fisheries confirmed a case of Rift Valley fever on a farm in the Jacobsdal area, about 100km from Kimberley, and Afrivet CEO, Dr Peter Oberem, yesterday confirmed that 250 sheep have since died on the farm as a result of the outbreak.
Oberem yesterday warned that cases reported so late in the season were “worrying”.
“Reported cases so late in the season – it is already winter in the southern hemisphere – is worrying. It’s not because we can expect a full-blown epidemic right away, but cases now point to a very good chance of a serious outbreak in summer,” Oberem stated, adding that the reason for this is that Rift Valley fever is caused by a virus that is transmitted by mosquitoes.
“They might be inactive in cold weather but the fact is that the mosquitoes have already feasted on the blood of infected animals.”
“This means that come summer, swarms will emerge as active carriers. If farmers do not take decisive preventative action now in winter, December could be a Rift Valley fever bloodbath,” Oberem warned.
Rift Valley fever is a devastating disease in small livestock, especially sheep. Up to 90% of lambs die within days of being infected, and between 40% and 100% of pregnant ewes that are infected will abort.
While it also occurs in cattle, buffalo and antelope, the disease is neither as virulent nor as fatal in those species as in sheep.
Rift Valley fever is furthermore a zoonotic disease, meaning it can spread from animals to people.
“While humans cannot be infected by mosquitoes, they are very likely to get ill if they come into contact with the blood of sick or dead animals and/or aborted foetuses. Veterinarians are therefore particularly at risk. During the last significant outbreak in South Africa, a young veterinarian from the Eastern Cape died of the disease. Although not always fatal in humans, the virus attacks the liver and recovery is slow and difficult.
The biggest mistake farmers can make is to be complacent in winter,” Oberem warned and urged farmers to vaccinate their livestock.
“Although sheep are more at risk, cattle should also be vaccinated to prevent mosquitoes feeding on them from ingesting and then transmitting the virus.”
Oberem explained that there are two types of Rift Valley fever vaccine, namely live and inactivated (or killed).
“The latter has to be used in animals that are, or could be, pregnant. Giving them the live vaccine would cause abortions or the birth of deformed lambs. The inactivated vaccine has to be given twice, unlike the live vaccine for which only one application is necessary. Farmers must be very careful when handling the live vaccine so as to not accidentally infect themselves.
“We have to control the disease while we have the opportunity to do so,” said Oberem.
“I am pleased that the state veterinary services have assured me that they are taking the matter seriously and are agreeing that farmers have to be warned to vaccinate now. If not, we will pay the price in livestock deaths and maybe even human casualties.
“An outbreak is also likely to hurt the export industry. Countries in the Middle-East have already banned South African lamb imports following the previous outbreak.
“Rift Valley Fever is a One Health concern because human activity in the environment aggravates it,” Oberem concluded.