A new awareness and blanket vaccination campaign to combat African horse sickness (AHS) in the southern provinces of South Africa is showing positive effects in critical and high risk zones, according to the president of the recently formed African Horse Sickness Trust.

Douglas Welsh, DVM, said that as a result of the Trust’s aggressive tactics, implemented in 2006, fewer horses are dying in the target areas and more horse owners are reporting the cases that do appear. As a result, new outbreaks in these areas are handled more efficiently.

The project’s primary target zones, George and Knysna in Western Cape, are now in the third year of the program, which runs from October to March. This season the program was extended for the first time into the Eastern Cape. These zones were selected because of their high risk and proximity to the protected “free” zone–an area that has never had AHS–located in Western Cape, he said.

“The first year, they had 40 horses die (in George and Knysna),” he said. “The second year, they had 16 horses die. This year they haven’t had a single case yet. The blanket vaccination clearly had a serious effect.”

Horses must be vaccinated at least three consecutive times in order to have “any sort of decent protection against horse sickness,” according to Truuske Gerdes, DVM, PhD, researcher in the Virology Department at the Onderstepoort Veterinary Institute and head of the World Organization for Animal Health reference center for AHS. “A single vaccination, if the challenge is high enough, is not going to do it.”

Although statistics in Eastern Cape are similar to last year, Gerdes believes that the Trust’s campaign there will eventually yield results similar to those in Western Cape.

Continuous, widespread vaccination is the key to minimizing the effects of the vector-transmitted disease that results in death in 80% of its unvaccinated victims, according to Welsh.

In South Africa, competitive sport horses must have proof of annual vaccination against AHS. However, the majority of horse owners do not do not use their animals for sport and have largely been unaware of how to effectively prevent AHS, according to the Trust Web site.  

Whereas the national rate of vaccination among horses was approximately 30% in 2005, the Trust’s goal is to spread the campaign throughout the country and see at least 70% of the horses vaccinated, Welsh said.

In the primary blanket vaccination zone, an estimated 90% of the horses were vaccinated this year, he said.

“Every horse that we could find, we just vaccinated them all,” Welsh said