According to government data, more than 100 horses in Africa died of African Horse Disease (AHS) when the Southeast Asian country first developed an illness that only affected animals.
"This disease has just occurred in Thailand. We have never had it in the past," said Sorawit Thanito, director general of the animal development department, on Thursday.
The government has quarantined sick horses to limit the spread of the disease, Sorawit said.
According to the latest government data, at least 131 horses have died in four provinces.
"We need to investigate how this virus got to Thailand," he said, adding that the government was informed about AHS in the country in late March.
Horses suffering from the disease can have a fever of over 39 degrees Celsius, difficulty breathing and bleeding in the eyes. No cases of AHS have been reported in humans and it has not been linked to the outbreak of the new coronavirus, Sorawit said.
The World Organization for Animal Health (OIE) suspended Thailand's "AHS-free country" status on March 27.
AHS is endemic to the central tropical regions of Africa, from where it spreads regularly to southern Africa and occasionally to northern Africa, according to the OIE.
AHS-free status was suspended in 2018 in Myanmar and Kyrgyzstan.
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