No end yet for African horse sickness

Although the current outbreak of African horse sickness (AHS) is not over yet and additional cases could be confirmed in the months ahead, there are encouraging signs that the situation in the worst hit areas in the Eastern Cape is stabilising.

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Favourable climatic conditions will, however, increase the spread of the Culicoides midge vector and therefore the spread of AHS, especially as higher than normal rainfall is predicted over most of SA for the next three months, said Dr Grietjie de Klerk of the Directorate of Animal Health. Since December there have been 42 confirmed outbreaks nationally, 19 of which were in the Eastern Cape.

So far, 92 suspected cases among horses have been reported in the eastern parts of the Eastern Cape. Of these, 64 were confirmed positive with 44 horses dying. More than 1 000 horses are under threat in this province alone. “The rainfall measured in the eastern parts of the Eastern Cape early in the season could explain the high number of outbreaks,” said De Klerk.

All horses in SA – except in the AHS-free and surveillance zones in the Western Cape – must be vaccinated annually using a registered vaccine at the cost of the owner. The AHS vaccine from Onderstepoort Biological Products (Reg No, G116, Act 36 of 1947) is currently the only registered vaccine. Furthermore, it was advisable to stable horses at least two hours before sunset and keep them stabled for at least two hours after sunrise, as this was when the midges are most active, said De Klerk.

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To prevent the introduction of the virus into the AHS-free zone, all movement of horses there were subject to state veterinary movement control, she said. Buffalo City state veterinarian Dr Stuart Varrie said the situation in the Eastern Cape had been exacerbated by the large numbers of horses kept in relatively close proximity without having been vaccinated, or only having been vaccinated infrequently.

“It is especially this group of horses that we were primarily concerned about and thus the distribution of vaccine was critical,” said Varrie. The vaccine distributed was supplied in part by the state (250 doses), the African Horse Sickness Trust (250 doses) and the Equine Research Centre of the University of Pretoria (100 doses).

The remaining vaccine was made available free of charge to private horse owners who have limited numbers of horses and who had approached the state veterinary office either directly or through their private vets. “These owners were, in the main, unable to vaccinate their horses for economic reasons,” said Varrie. AHS is a controlled disease, and reporting outbreaks to the state veterinary services is compulsory.