African horse sickness: controlling biting midges

With the rainy season upon us in the African horse sickness-infected zone, it is crucial that horse owners keep a close eye on their animals’ behavior and implement strict control of flying insects, says Dr Mac. This is especially important due to the apparent vaccine shortage.

- Dr Mac

This is not the first time that Onderstepoort Biological Products (OBP) has run out of African horse sickness (AHS) vaccines at the beginning of the rainy season. AHS is a highly infectious and fatal disease of horses, and is transmitted by the Culicoides biting midge. The midge breeds in muddy puddles around stables, and hatches after the first rain of the summer season. The most effective way to prevent AHS in horses is through the OBP vaccine, which is administered to horses in two doses, with a threeweek rest period between doses.

OBP suggests that horses be vaccinated in late summer. However, based on other research, many veterinarians recommend that they be vaccinated between 1 June and 31 October. This is because there is no rain in the AHSinfected zone during winter, and very little chance of horses becoming infected. Moreover, by vaccinating in winter or early spring, horses will be fully vaccinated by the time the rain starts and the midges begin to proliferate.