SOUTH-EAST Asia has confirmed its first ever outbreak of African horse sickness (AHS).

This infectious disease – which is the most lethal viral disease of horses known – can affect all equine species, resulting in a high fever, difficulty breathing, coughing and frothy discharge from the nostrils. The mortality rate is very high, with up to 95% of horses experiencing acute respiratory issues dying within a week.

The infection can also manifest in cardiac form, with horses experiencing loss of the ability to swallow and possible colic symptoms, pinpoint bleeding in the membranes of the mouth and eyes. This can lead to a mortality rate of around 60% with deaths resulting from heart failure. The virus is transmitted through midges and once a horse has been bitten by a carrier midge, the incubation period of AHS is usually seven to 14 days, but may be as short as two days.

Samples from Thailand were confirmed AHSV positive by scientists based at The Pirbright Institute, and further testing established that AHSV 'serotype 1' had caused the outbreak; the first time that this serotype has been seen outside of Africa.

Renowned Thai equine vet Dr Siraya Chunekamrai has called for urgent help to contain the outbreak, which has already killed 500 horses in Thailand and has the potential to kill thousands more. She herself is treating many affected animals and leading urgent vaccination efforts by equine veterinary volunteers in the country. She has also launched an international fund-raising appeal to support the purchase of essentials, including vector protection nets to protect horses from midges. Netting and stables are also required to be sprayed with pyrethroid insecticide.

She explained: “This outbreak is particularly deadly with horses dying quickly. They present with acute signs and with both cardiac and pulmonary forms. The mortality rate is very high at around 95%.

“This is a welfare disaster for hundreds, possibly thousands of horses in Thailand. It is equally disastrous for their owners, many of whom depend on them for their livelihood. Despite the restrictions in place because of the COVID-19 pandemic, veterinarians across the country are working tirelessly to reduce the suffering of horses in Thailand and to help owners to protect their animals."