African horse sickness (AHS) is a highly infectious and deadly disease caused by the African horse sickness virus. Animals affected are all breeds of horses (mortality rate of 70-90%), mules and donkeys. It is caused by a virus of the genus Orbivirus belonging to the Reoviridae (Reoviridae is a family of viruses.). Wildlife Equine species (Zebras) are resistant to the disease. The vector host, Culicoides midge, spreads AHS virus.
How can your horse contract AHS?
AHS is not directly contagious but is known to be spread by insect vectors instead. This means your horse cant catch AHS from another horse by being in contact with it. The infected midge which bits the horse and infects the horse becomes infected when feeding on other infected equine species. So it really is a vicious cycle. This midge occurs mostly in the warm, rainy season when there are lots of midges around, and disappears after frost as they can not survive in cold weather. Most animals become infected in this warmer period and can be associated with sunset and sunrise when the midges are most active.
One of the big concerns with an outbreak of AHS is that although the disease may not be communicable in the traditional sense is still can be sped the midge insect. If the infected midge where to travel home with you on your horse, for example, you could be putting the next locations horses at risk of being bitten.
The disease manifests in three ways, namely the lung form, the heart form and the mixed form. The lung (dunkop) form is characterised by the following symptoms.
- very high fever (up to 41 degrees).
- difficulty in breathing, with mouth open and head hanging down.
- frothy discharge may pour from the nose.
- sudden onset of death.
- very high death rate (90%).
The heart (dikkop) form is characterised in the following manner:
- fever, followed by swelling of the head and eyes.
- in severe cases, the entire head swells (“dikkop”).
- loss of ability to swallow and possible colic symptoms may occur.
- terminal signs include bleeding (of pinpoint size) in the membranes of the mouth and eyes.
- Slower onset of death, occurring 4 to 8 days after the fever has started.
- Lower death rate (50%).
The mixed form is characterised by symptoms of both the dunkop and dikkop forms of the disease.
If you suspect any of the above symptoms do not hesitate to contact your local vet as this diagnosis can only be confirmed by testing the virus in a laboratory. It is, therefore, essential that blood samples be taken from the horse during the fever stage of the disease. As AHS is a controlled disease, you as the owners are obliged by law to notify the local State Veterinarian of suspected cases.
Treatment and Prevention
Uninfected horses are vaccinated against the virus. Three vaccines currently exist, which include a polyvalent vaccine, a monovalent vaccine, and a monovalent inactivated vaccine. This disease can also be prevented by destroying the insect vector habitats and by using insecticides. Keep the stable areas clean and dry will also help limit the midge numbers in your stables. The constant use of Tabard or Peacefull sleep on your horses can also help prevent bits. It's also important to keep your horse in the stable for longer periods of time especially early mornings and late afternoons when the insects are most active.
Remember there is no cure for AHS so prevention is key. Always be aware of how your horse is feeling because early detection could save your horse's life, and make sure you're helped protect your horse against getting bitten. Please note that all info in this blog is subjective to my own experience I am not a vet and if you have any concerns about your horse always consult a vet first.
If you'd like some more info on this disease go check out the link below.-