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Home: Veterinary Services: Animal Health: AFRICAN HORSE SICKNESS

What is African horse sickness?

African horse sickness (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 horse sickness 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.

Symptoms

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

In the lung (dunkop) form, the first symptom is a very high fever (up to 41 °C), whereafter the horse starts breathing with great difficulty, often with its mouth open and its head hanging down. A large quantity of frothy discharge may pour from the nose. This form is characterised by a very high death rate, with horses dying suddenly.
The heart (dikkop) form of the disease usually takes longer to develop with a death rate of about 50 % in affected horses. Death occurs 4 to 8 days after the fever has started. The main symptom is a swelling of the head and eyes. The sunken areas above the eyes swell so severely that the horse can often only half open its eyes. In severe cases, the entire head swells ("dikkop"). Terminal signs of this form are bleedings (of pinpoint size) in the membranes of the mouth and eyes. The horse also loses the ability to swallow, and water and pieces of food may drip from the nose and mouth. Severe stomach pain may also occur (colic symptoms).
The other form of this disease is the mixed form, where symptoms of both the dunkop and dikkop forms may occur.

Diagnosis

An initial diagnosis of African horse sickness 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 horse sickness-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 horse sickness 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:

Keep your horses in closed stables from at least 1 hour before sunset until at least 1 hour after sunrise. This will ensure that no midges come into contact with your horses to infect them.
Apply suitable insect repellents or insecticides to your animals' coats to keep the midges away.
Take the rectal temperatures of all horses, mules and donkeys twice a day in order to identify infected animals as early as possible. If there is any increase in temperature, consult your veterinarian immediately.
Vaccinate all your horses, if you have not already done so. This does not apply to the African horse sickness control area, except with the permission of the Director: Veterinary Services (see above).

Is there AHS in your stable or on your property?

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

fever
sweating
lack of energy
breathing difficulties
coughing
discharge from the nose
too much saliva
restlessness
swelling of the eyes and/or head.

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 horse sickness must be reported to your nearest state veterinarian, because this is a controlled disease (under the Animal Diseases Act No. 35 of 1984).

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).

Control

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 horse sickness 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.

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 horse sickness 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 horse sickness, consult your nearest state veterinarian.

We are committed to keeping African horse sickness 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
Tel: (012) 319 7459 Fax: (012) 329 0499

The Director Veterinary Services (Western Cape Province)
Dr G Mzisa
Tel: (021) 808 5001/2

The State Veterinarian Boland
Private Bag X1, Elsenburg, 7607
Tel: (021) 808 5253 Fax: (021) 8085125

OR 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. 1999.