During today’s Canadian Equine Infectious Disease Surveillance call, Dr. Alison Moore from the Ontario Ministry of Agriculture Food and Rural Affairs gave an update on equine infectious neurological disease cases in the province. Prominent amongst those disease is eastern equine encephalitis (EEE). This very mosquito-borne viral infection is fortunately pretty rare in horses and is very rare in people in Ontario. But, rare doesn’t mean it doesn’t exist.

Last year was a bad EEE year in horses, with 24 confirmed cases in Ontario. Of those, 22 died or were euthanized, which is typical of this disease (if anything, it’s surprising that 2 survived). These cases occurred over a stretch from the end of July to the end of October. That’s well above the usual number of cases for the province, but this is a disease that can vary quite a bit year-to-year. Various neighbouring states and provinces had similarly bad years.

Fortunately, 2015 seems to be a better year. While the EEE season isn’t quite over yet, there have only been four confirmed cases in horses. All four died or were euthanized, and all occurred in Eastern Ontario, where we find most EEE cases.

A vaccine is available against EEE, and there is often debate about whether to vaccinate against a disease that is very rare, but at the same time is very bad. It’s a discussion horse owners should have with their vets, to determine the risk to their own horses and whether they want to vaccinate. As with any mosquito-borne disease, controlling mosquitoes and mosquito exposure is also important, but that’s often easier said than done.

A podcast of this month’s surveillance call will be available in the near future on the Equine Canada website.

Below is a map showing the areas in which cases of infectious equine neurological disease were diagnosed in Ontario in 2015.  A larger version of the map can be seen on the OMAFRA website.

Equine NeuroDz Surv Oct2015