More than 500 horses have died of AHS in Thailand since the outbreak appeared in late February 2020
The origins of the horse disease are being investigated, with evidence pointing to asymptomatic zebras (legally imported without needing blood samples or quarantine) as the source of the infection – a biosecurity gap that was closed last month [April 2020]
The Horse.com article - As African horse sickness (AHS) continues to spread across Thailand, horse owners seek vaccines and Cambodia works to protect horses on its Thai border...
OIE report and stats
AHS is a highly infectious and almost invariably fatal equine disease transmitted by insect vector (biting midges) between ALL Equidae, e.g. horses, donkeys, mules, zebras.