African Horse Sickness Strikes Malaysia
As Thailand’s horse industry is starting to recover from its African horse sickness (AHS) outbreak, with thousands of horses vaccinated, the neighboring country of Malaysia is addressing its first cases of the disease.

Five horses on the same property in the Malaysian state of Terengganu have tested positive for AHS, according to a Sept. 2, 2020, report from the World Organization for Animal Health (OIE) in Paris, France. Four of the horses have shown signs of disease, including fever and breathing difficulties.

Located about 200 kilometers (125 miles) from the southern Thai border, Terengganu is part of the peninsula on the western side of the Gulf of Thailand. It’s separated from Thailand’s initial outbreak site in the Pak Chong district by about 1,500 kilometers (930 miles) over land. Across the gulf waters, the distance is about 1,000 kilometers (650 miles).

The five affected horses in Terengganu were kept in the owner’s backyard, Dato’Dr Norlizan Mohd Noor, deputy director general of veterinary services in Malaysia’s Ministry of Agriculture and Agro-Based Industry in Putrajaya, reported to the OIE.

In early August, two of the horses presented with lameness and difficulty breathing, but attending veterinarians could not confirm the respiratory issues during an on-site visit, Mohd Noor reported. By mid-August, a third horse had fever and respiratory distress and received antibiotics and steroids. Three days later, a fourth horse became lame with significant inflammation in a hind limb. The treating veterinarian decided to send blood samples for analysis to the country’s Veterinary Research Institute (VRI) in Ipoh, which confirmed the disease as AHS. On Aug. 31, veterinarians returned to the property for additional sampling of blood, nasal discharge, and eye discharge from all five horses. Analyses confirmed AHS in all five horses.

Analyses haven’t yet revealed the serological type of the virus, said Shri Kanth, DVM, chairman of the veterinary committee of the Equestrian Association of Malaysia (EAM) and national head veterinarian of Malaysia. The VRI is currently carrying out this investigation, he said. In April, the Pirbright Institute in the U.K. identified the Thai outbreak’s virus as Type 1 AHS. Kanth has ordered tight biosecurity and vector control measures (protecting horses from biting midges) within the state of Terengganu, he said. No horses can move in or out of the state, but movement is still authorized elsewhere in the country, although moving horses from one property to another is “not encouraged,” he added. The EAM has canceled equestrian events due to the outbreak.

The five affected horses are to be euthanized, according to the OIE report.

Biting midges can transport the AHS virus as far as 150 kilometers (about 93 miles) across land or 700 kilometers (about 435 miles) across water, according to Evan S. Sergeant, PhD, of the AusVet Animal Health Services, in Canberra, Australia.

This is the first time Malaysia has reported a case of AHS, according to the OIE; after Thailand, it is the second country in Southeast Asia to do so. Thailand’s last reported case to the OIE was on June 16, in Bangkok, near the initial outbreak site of Pak Chong.

In response to the initial outbreak, the American Association of Equine Practitioners released its African Horse Sickness guidelines in July.