Deadly virus killing horses in Thailand
WHEN horses suddenly started dying in Thailand as the nation locked down to stem the spread of Covid-19, researchers feared the cause was another deadly bat-borne virus that could kill humans.
“We had no idea what was causing it,” said Nopadol Saropala, owner of a horse farm about 160km from the Thai capital, who lost 18 horses in nine days.
“We found out later that it came from zebras that were apparently in transit to China.”
More than 500 horses have died since the outbreak appeared in late February.
Blood samples analysed in England in March confirmed it was African horse sickness, a viral disease not known to harm humans but which is widespread among equines, including zebras, in Africa.
The illness, spread by biting midges, hadn’t broken out in Asia in more than 50 years.
The disease has devastated horse owners in Thailand and sent another signal to the global health community about the potential dangers of the wildlife trade.
About 70% of emerging infectious diseases in humans are zoonotic – transmitted from animals to people.
The severity of the Covid-19 outbreak, thought to have originated in bats, has prompted governments from the US to Australia to increase funding for studies of relationships between animals, humans and the environment to detect potential contagions before they jump species.
Climate change, growing populations, consumerism, poverty, conflict, and migration are all factors in the spread of modern global health problems, a group of specialists wrote in the Lancet medical journal on May 16, calling for a multidisciplinary coalition to look into Covid-19.
Since 1980, four pandemics or international outbreaks – SARS, Ebola, AIDS and Covid-19 – have been tied to the wildlife trade.
Other animal-bound pestilence, such as bluetongue, avian influenza, and African swine fever have added to the mounting costs of disease.
“A stronger surveillance system into parts of wildlife, in particular the ones that are the source of many of these viruses and which we may come into contact with, would be very helpful,” said Peter Ben Embarek, a food safety and animal disease scientist with the World Health Organisation in Geneva.
While a Thai government investigation continues into the origins of the horse disease, evidence points to zebras – asymptomatic carriers – that were legally imported without needing blood samples or quarantine. That biosecurity gap was closed last month.
One locally registered firm involved in importing the animals since September 2018 had also been exporting them, especially to China, according to an April 7 statement by Thailand’s Department of National Parks.
“No one was thinking of a disease from Africa,” said Siraya Chunekamrai, a Bangkok-based veterinarian involved in efforts to contain the outbreak.
“The first thought is to expect something local.”