National Department of Agriculture
Directorate Animal Production and Health

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African Horsesickness

What is African horsesickness?

African horsesickness (AHS) is a serious insect-borne disease of horses, mules and donkeys which is spread by a virus. It is endemic to (occurs naturally on) the African continent, and is characterised by respiratory and circulatory damage, accompanied by fever and loss of appetite.

How do horses contract the disease?

African horsesickness does not spread directly from one horse to another, but is transmitted by midges, which become infected when feeding on infected horses. It occurs mostly in the warm, rainy season when midges are plentiful, and disappears after frost, when the midges die. Most animals become infected in the period from sunset to sunrise, when the midges are most active.


There are three forms of the disease, namely the lung form, the heart form and the mixed form.


An initial diagnosis of African horsesickness can be made based on the symptoms displayed. This diagnosis must be confirmed by identifying the virus in a laboratory. Blood samples should be taken from the horse in the fever stage of the disease. When a horse has died, samples of the spleen, lungs and lymph nodes should be analysed.

Consult your veterinarian or nearest laboratory for advice in this regard.

Prevent the disease from entering your stable or property

A vaccine is available for use in South Africa. However, its use is not permitted in the African horsesickness-free or surveillance zone of the Western Cape Province (see maps). To obtain the vaccine in these zones, the Director: Veterinary Services of the Western Cape must be requested to give written permission.

In terms of the Animal Diseases Act (Act No. 35 of 1984), all horses, donkeys and mules must be vaccinated annually with an approved African horsesickness vaccine. The best time to vaccinate is in September, before the warm, rainy season starts. The vaccine consists of 2 doses given 3 weeks apart. The animals may only get light exercise during the period up to 3 weeks after vaccination, especially those animals vaccinated for the first time.

Foals of vaccinated dams can be vaccinated at or after 6 months of age. Foals of unvaccinated dams must be vaccinated earlier because they have not received immunity from their dams. They may be vaccinated from as early as 1 to 2 months of age.

The owner may vaccinate his animals, but if a vaccination certificate is required for any reason or a permit is required to move horses to the Western Cape Province, then vaccination must be performed by a registered veterinarian.

During outbreaks of the disease:

Is there AHS in your stable or on your property?

Look out for any symptoms of illness in your horses, such as:

If any of these symptoms occur, put the horse in a separate closed stable and consult your veterinarian as soon as possible. All cases, or even suspect cases, of African horsesickness must be reported to your nearest state veterinarian, because this is a controlled disease (under the Animal Diseases Act No. 35 of 1984).

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Why it is important to control this disease

AHS is a very serious disease because of the high death rate in affected horses. There is no effective treatment for the disease and medicine to treat the symptoms is very costly. Performing horses cannot be trained for some time (when treatment is given, the horse needs absolute rest and a gradual return to activity).


According to the Animal Diseases Act (Act No. 35 of 1984), all horses, mules and donkeys must be vaccinated annually. Animals in the free and surveillance zones in the Western Cape, however, may not be vaccinated unless the written permission of the Director of Veterinary Services has been obtained (see address on p 4). Ask your veterinarian for further information about vaccination.

There are strict rules for taking horses, mules and donkeys into the Western Cape Province. An animal must have been fully vaccinated, not sooner than 2 months and not longer than 24 months before entry, against African horsesickness by a registered veterinarian, and the details of the vaccination must be entered into its passport. A valid, up-to-date health certificate, issued not more than 48 hours before entry into the province, is also required, and your veterinarian must notify the State Veterinarian Boland beforehand that the animal will enter the area.

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For more details of the moving of horses, mules and donkeys into the Western Cape Province, contact the State Veterinarian Boland, who is the main agent responsible for the control of African horsesickness in this province (see contact details).

The control of the disease can only be effective if there is total cooperation between the Government and all horse owners in the country.

For any advice with regard to African horsesickness, consult your nearest state veterinarian.

We are committed to keeping African horsesickness out of the free zone of the Western Cape Province and will use all possible means to do so.

For further information, please contact:
The Directorate Animal Production and Health, Private Bag X138, PRETORIA 0001

The Director Veterinary Services (Western Cape Province), Dr R Visser

The State Veterinarian Boland, Private Bag X5055, Stellenbosch 7599

Your local state veterinarian


Compiled by Directorate Communication, National Department of Agriculture
in cooperation with
Directorate Animal Production and Health

Printed and published by National Department of Agriculture
and obtainable from
Resource Centre, Directorate Communication, Private Bag X144, Pretoria 0001, South Africa