BANGKOK – For the first time in Thailand, another rapidly spreading “cruel” and “devastating” virus has killed at least 186 horses by attacking the animals’ lungs, causing fever and often resulting in death within hours.
Thailand’s security forces on April 10 guarded checkpoints on highways to stop horses from being transported across the Southeast Asian country, and quarantine animals infected with the African Horse Sickness (AHS) virus.
The sudden emergence of AHS coincides with the kingdom’s spreading Covid-19 outbreak and tightening social controls, but the two viruses are not related. There are no recorded cases of humans becoming infected with AHS anywhere in the world.
Other regional nations have been notified of Thailand’s AHS outbreak so they can look for symptoms and check horses in their countries.
Thailand will now face new difficulties exporting horses and other equines to the European Union, United States and elsewhere, including for competition in horseraces, shows and other events.
“Effective immediately, and until further notice, the US Department of Agriculture’s Animals and Plant Health Inspection Service’s Veterinary Services is placing restrictions on the importation of equine from Thailand, based on the diagnosis of African Horse Sickness in multiple equine species of different ages and sexes,” the US department announced on March 31.
The New York Animal Import Center, located in Rock Tavern, New York, is the only US quarantine location accepting horses from AHS countries. Imported animals to the US must be held for 60 days.
“Any semen or embryos from countries affected with African Horse Sickness is prohibited,” the department said on its website.
Thailand’s health officials have established a disease control center and deployed teams to test suffering horses, and spray disinfectant and insecticide in barns and stables.
A hotline was created so people could inform authorities about any illegal transportation of horses.
International veterinarians usually take a blood sample from a live horse, or a spleen specimen at post-mortem, to confirm AHS.
Most of the 186 horses died at the epicenter where the AHS virus killed 162 horses in northeast Thailand’s Nakhon Ratchasima province, also known as Korat, the country’s self-designated “cowboy” region.
“Uthen Chatphinyo, owner of a racehorse farm in the province, said AHS has killed 21 of his 160 horses,” the Bangkok Post reported.
Nopphadon Sarobon, the owner of another horse farm, said he had lost 20 horses that he had bred for sale. Each horse had a price tag ranging from 400,000 to 800,000 baht (US$12,300 to $24,600), the report said.
The first death was reported in March in that province’s Pak Chong district, said Department of Livestock Development director-general Sorawit Thanito.
An additional 13 deaths occurred in Prachuap Khirikhan province 50 miles south of Bangkok on the Gulf of Thailand, plus five in Chonburi, three in Ratchaburi, two in Phetchaburi and one in Chaiyaphum provinces, the government-owned Thai News Agency reported on April 6.
“This disease has just occurred in Thailand. We’ve never had it in the past,” Sorawit said, according to Reuters. “We have to investigate how this virus got to Thailand,” he said.
Thailand was deleted from the “AHS-Free Country” list by the Paris-based World Organization for Animal Health on March 27 after Sorawit reported the first 42 deaths.
“Unofficial sources report these to be racehorses,” said the International Disease Monitoring unit of Britain’s Department for Environment, Food and Rural Affairs on March 31.
No horses from Thailand were legally shipped to the United Kingdom after December 2019, the monitors said.
The disease can attack horses, donkeys, mules and zebras, plus camels and dogs, according to the England-based Pirbright Institute, which develops “novel vaccines for viral diseases of livestock, and is actively working on a promising vaccine candidate for AHS.”
There is no known cure or reliable vaccine for the disease. Non-steroidal anti-inflammatory drugs can alleviate pain or reduce fever.
“It can be spread through the blood, and infects namely the lungs, spleen and other lymphoid tissues,” the institute said.
Symptoms can include fever, a loss of appetite, and swelling around horses’ eyes, lips, cheeks, tongue and neck.
The virus is infectious but not contagious from horse to horse. It requires transmission by tiny, two-winged flies which resemble gnats.
“AHS is spread by biting midges — culicoides — and dogs can become infected by eating contaminated horse meat,” the Pirbright Institute said.
Culicoides can also give horses severe, non-fatal skin diseases.
Most of the world’s AHS cases appear in sub-Saharan Africa but are also found in the Middle East, Pakistan, India, Morocco, Spain and Portugal.
“For several centuries, the devastating [AHS] has been a cruel scourge to horse owners,” said the National Institutes of Health (NIH) based in Bethesda, Maryland.
AHS has “a 70% mortality rate,” it said. “The geographic distribution of the midge vector broadens with global warming and climate change.”
In the mid-1800s, the virus killed almost 70,000 horses within 10 years in South Africa.
The most deaths occurred during 1959-63 across the Middle East and Southwest Asia, killing more than 300,000 horses, the NIH said.
That outbreak was halted thanks to experimental vaccines and the huge toll of dead horses, which limited the number of surviving susceptible animals.
Richard S. Ehrlich is a Bangkok-based American correspondent reporting from Asia since 1978.