AHS Deaths Near 500 in Thailand, Vaccination Begins

As veterinarians rush to vaccinate Thai horses against the deadly African horse sickness (AHS) virus, the outbreak continues to create a path of destruction, said local officials. With a death toll now standing at 463 horses, AHS is spreading east and west from its initial outbreak site in central Thailand.

More than 400 of the deaths have been recorded in the Nakhon Ratchasima province, where veterinarians first identified the disease following the sudden death of 40 horses in the province’s Pak Chong District last month. An additional 62 horses have died as of April 28, as the disease has progressed southwestward into provinces along the Gulf of Thailand toward Malaysia and eastward toward Cambodia, the Thai Equestrian Federation reported.

Meanwhile, vaccination programs began April 19, according to government reports to the World Organisation for Animal Health (OIE) in Paris. The first horses to receive vaccines were the animals used in the snake venom and rabies antidote development center of the Thai Red Cross Society in the Phetchaburi province. Although the center is 350 km (217 miles) from the initial outbreak site, the 560 Red Cross horses received priority vaccination because of their role in human medicine.

“It impacts human health if the country loses our ability to produce vaccines,” said Siraya Chunekamrai, DVM, PhD, treating veterinarian and AHS task force member with the Ministry of Agriculture Department of Livestock Development (DLD).

Vaccination began April 20 for all horses in the seven affected provinces as well as those horses within 50 km (31 miles) of affected farms, the DLD reported.

The live, attenuated vaccine could, in some cases, create its own, less severe form of disease with viral spread. Therefore, vaccinated horses must remain quarantined under tight netting for 30 days. Netting must effectively stop the passage of any biting midges, the 1-millimeter flying insects that transmit the virus from horse to horse, said Camilla Weyer, BVSC, MSC, PhD, senior research officer and AHS control manager at South African Equine Health and Protocols, in Somerset West.

The ongoing quarantine is hard on both owners and horses. “Horses only stand in the individual stall covered by the net,” said Wipawan Pueng, co-founder of The Horses Endurance Stable, in the Nakhon Ratchasima province, and an FEI endurance rider. “It’s been almost five weeks in the net (with three more to go following last week’s vaccination). We just can hand-walk them in the stable building.”

Meanwhile, Cambodia has begun preventive measures along its western border, said Chunekamrai. “(Thailand’s) Sra Kaew province near the (Cambodian) border has been protected, with nets and vaccinations complete,” she said. “The Cambodia pony welfare organization has contacted the government and local authorities to enter the provinces and work with pony owners to create awareness and put up nets.”

Back at The Horses Endurance Stable in the initial outbreak zone, the horses—mostly imported Arabians—tolerated the vaccine well, with the exception of one horse with “very high temperatures,” said Pueng. “We’re just keeping a close watch on him,” she said.

It’s an emotional time for these owners and riders who are constrained to respect strict individual box stall quarantines for their horses as well as social distancing for themselves in the context of the human COVID-19 pandemic, Pueng said. It’s particularly challenging for these high-level sport horses that are accustomed to covering long distances regularly, she added. Pueng and Prutirat R. Serireongrith, who owns the horses at the stable, have taken their endurance mounts to world championships and World Equestrian Games across the globe, but they’re now finding their athletes locked up with nothing but hand-walking for exercise.

“Mulawa Angelus is my heart, my favorite, my buddy,” Pueng said of the 17-year-old Arabian gelding imported 12 years ago from Australia. Winning multiple races in Asia, competing across Europe, and carrying Pueng to 14th place at the 2014 Alltech FEI World Equestrian Games in Normandy, France, Mulawa Angelus is now a “survival horse” living in a “netted world,” said Pueng. “I just pray for him every single minute to survive in this catastrophe,” she said.