Ten years ago when 14 horses fell ill — one of which died — at a Pune farm, scientists at the National Institute of Virology (NIV) conducted a series of tests to rule out Bluetongue virus, African horse sickness and other diseases that affect equines. Now, a decade later, they have been able to identify the cause of death: the horse had been infected with the equine encephalosis virus (EEV). The presence of the virus in India has also fuelled concern among the scientists as the country is home to several species of midge that can spread the virus. In the absence of specific treatment or vaccine, the best way to control the spread of the virus is to limit horses’ exposure to midges, scientists say.
“The presence of EEV in India is a cause for concern because several species of Culicoides midge (small flies), which play a major role in EEV’s transmission, are present in the country,” Pragya Yadav, a group leader for the maximum containment laboratory at NIV, told The Indian Express.
The Emerging Infectious Diseases journal of the Centers for Disease Control and Prevention published the study online on April 10. EEV is a noncontagious viral disease of equids (mainly horses). It causes fever, loss of appetite and weakness. The virus spreads from horse to horse through insects, specifically biting midges.
First isolated from horses in South Africa in 1967, EEV was considered to be limited to that region but a 2008 outbreak in Israel highlighted the potential of the virus to spread. Fears were fuelled further when in the same year, several horses at a farm in Pune became ill with similar symptoms. One of them died. Genetic analysis (next-generation sequencing) identified the virus in the dead horse as EEV, Yadav said. “In July 2008 we received samples such as blood and organ tissue from the dead horse. Why we could not identify the virus earlier was due to the lack of new detection techniques. As this was a new virus and no diagnosis was available, we were not able to identify it. At that time, available pathogens, for instance, Bluetongue virus and African horse sickness which affect equines, were tested. But we could not identify this virus. New technology — next-generation sequencing that works on novel pathogens — helped identify the virus,” Yadav said. The complete genome of EEV isolated from the dead horse confirmed the presence of EEV in India.
“The EEV findings have been relayed to the Department of Animal Husbandry, Dairying and Fisheries under the Ministry of Agriculture and Farmers’ Welfare. “The Department of Animal Husbandry should initiate a survey to provide information about EEV’s presence in equine centres and commercial farms and to screen samples from sick horses. The concern is, this virus may be widely circulating in India without having been noticed earlier,” Yadav said.