Learn about AHS and the protocol around prevention

African Horse Sickness (AHS) is a viral disease that causes severe respiratory and cardiovascular symptoms (and frequently death). The disease is transmitted by midges; hence the recommendation is to ensure all horses in the infected zone are vaccinated before the ‘midge season’; that is before 31 October each year. 


1 June-31 October is the recommended time to vaccinate as the midges are low in number during this time. The virus has 9 serotypes, thus two separate vaccines are needed; all adult horses should be vaccinated each year with both. A vet is required to do the vaccination for competition horses, or those that are to be moved to another zone (speak to your vet regarding movement requirements and permits). The Western Cape Province has various zones of control where horses may not be vaccinated, but the rest of the country is the ‘infected zone’ where vaccination is required.

No vaccine is 100% fail-proof, especially regarding AHS and the multiple serotypes and variance; thus, in addition, we strongly recommend applying midge repellent daily, keeping horses away from marshy areas and stabling during high-risk periods for midges (dawn and dusk are high activity periods for midges, thus stable horses from late afternoon through the night until mid-morning).


Fever, swollen head, difficulty breathing, frothy nasal discharge, sudden death. AHS is a controlled disease; any suspicious cases should be reported.


Treatment is supportive only, since the disease is caused by a virus. A vet will be able to format the best treatment; there is a fair amount of ‘boereraad’ out there with some harmful products being advised that do no good. There is no scientific evidence that these remedies work and can be harmful to your horse. 

Key points:
  • Vaccinate your horse yearly before 31 October with a registered vaccine
  • Report all cases with symptoms suspicious of AHS
  • The movement of horses to the Western Cape zones requires a permit