Email* On Aug. 10, 2019, the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) was notified of a confirmed case of eastern equine encephalitis (EEE) in a horse located in the United Counties of Leeds and Grenville, ON. The unvaccinated mare was euthanized following the sudden onset and progression of neurological signs. Laboratory diagnostic testing confirmed infection with the EEE virus (EEEv).EEE is not transmissible from horses to people.Effective equine vaccines for EEE are available and veterinarians should encourage clients to keep their horse’s vaccinations current. Once clinical infection develops, treatment options are limited to supportive care. The mortality rate in unvaccinated horses is high.Veterinarians in Ontario should consider EEE as a differential diagnosis in horses exhibiting neurological signs and can identify positive cases through appropriate testing. IgM antibodies to the EEEv can be detected in serum from horses with neurological signs.Clinical signs of EEE, including circling, head-pressing, ataxia and depression, can mimic a variety of encephalitides, including rabies, West Nile virus (WNV), botulism, hepatic encephalopathy, equine protozoal myeloencephalitis, and equine herpes myeloencephalopathy. Most equine cases of EEE in Ontario occur between the months of August and October and end with the onset of frost.EEEv affects mainly equine species in eastern North America but can rarely cause severe disease in humans. EEEv has also caused fatal infections in pheasants, quail, emus, alpacas, llamas and dogs.EEEv has been reported in horses in Ontario since 1938. Equine neurological cases are posted on the OMAFRA website at http://www.omafra.gov.on.ca/english/livestock/horses/westnile.htm.Ontario’s local public health units are conducting mosquito surveillance for both WNV and EEEv. Birds are the natural hosts for both viruses, which are transmitted to horses and humans by mosquitoes which have bitten an infected bird. As of Aug. 7, 2019, no mosquito pools have tested positive for EEEv (https://www.publichealthontario.ca/en/DataAndAnalytics/Pages/WNV.aspx).Questions about EEE in horses can be directed to:Dr. Alison MooreLead Veterinarian – Animal Health and WelfareOntario Ministry of Agriculture and FoodTel: (226) 821-0364E-mail: [email protected] Tags: Eastern Equine Encephalitis, EEE, EEEV, We’ll send you our regular newsletter and include you in our monthly giveaways. PLUS, you’ll receive our exclusive Rider Fitness digital edition with 15 exercises for more effective riding. Horse Sport Enews SIGN UP Subscribe to the Horse Sport newsletter and get an exclusive bonus digital edition! More from Horse Sport:Christilot Boylen Retires From Team SportAfter an exemplary career as one of Canada’s top Dressage riders, seven-time Olympian Christilot Boylen has announced her retirement from team competition.2020 Royal Agricultural Winter Fair CancelledFor only the second time in its history, The Royal Agricultural Winter Fair has been cancelled but plans are being made for some virtual competitions.Royal Agricultural Winter Fair Statement on 2020 EventAs the Province of Ontario starts to reopen, The Royal’s Board and staff will adhere to all recommendations put forward by government and health officials.Government Financial Assistance for Ontario FarmersOntario Equestrian has recently released this update of several financial assistance packages available, including those for farm business.