African Horse Sickness
A widespread outbreak of African horse sickness (AHS) has been reported in Thailand, the first time AHS has occurred outside the African region in 30 years.
- Thailand continues to provide weekly updates to the OIE on the AHS outbreak, which has now spread to twelve provinces and caused the death of almost 550 horses.
- The diagnosis of AHS was confirmed by the Thai National Institute of Animal Health and by the OIE reference laboratory for AHS at Pirbright in the United Kingdom.
- The source of introduction of AHS to Thailand is still under investigation, with media sources implicating imported zebras.
- Thailand has commenced vaccinating horses in affected areas, using an attenuated live polyvalent vaccine from South Africa.
AHA has commenced a review of the AUSVETPLAN disease strategy for African horse sickness.
African horse sickness
- African horse sickness (AHS) is the most serious known viral disease of horses, resulting in up to 80-90% mortality in affected horses.
- The AHS virus (AHSV) is spread by midges of the Culicoides species that prefer to feed on horses.
- Zebras are the natural reservoir hosts of AHSV in Africa, and they may carry the virus without showing any signs of disease.
- Long distance spread of AHS can occur with the movement of live equids (horses, donkeys, mules, zebras), or infected insect vectors.
- The last major outbreak of AHS outside of Africa occurred in Spain and Portugal in 1987-90, following the importation of wild African zebras.
- The disease does not affect humans.
Australia has strict import conditions on equids to prevent the entry of AHS (and other equine diseases) into Australia.
- Control measures during an incursion are aimed at reducing horse contact with vectors and include:
- housing horses under midge-proof netting
- using insect repellants on horses
- insecticides and other measures to reduce insect populations in the environment
- preventing vectors feeding on infected horses.
- An attenuated (weakened) live vaccine, available in Africa, will be used in Thailand to protect horses. The vaccine can be associated with severe side effects in some horses.
- The vaccine is not available for use in Australia.
What to look for
Horses with AHS may show:
- swelling of the face and eyelids, with reddened eyes
- swelling of the brisket and front half of the horse
- difficulty breathing, with or without frothy discharge from the nostrils
- rapid deterioration and death.
Further information on the outbreak in Thailand
- OIE Webinar recordings
- Thailand scrambles to contain major outbreak of horse-killing virus
- Pirbright confirms African horse sickness in Thailand