‘Tis the season…

Eastern equine encephalitis (EEE) is a very serious disease that’s fortunately rare in Ontario, but when it happens, it’s bad news. It’s a viral disease transmitted by mosquitoes (similar to West Nile virus), and we often see a couple of horses affected every year, usually starting around now (late August) and extending into the fall.

The Ontario Ministry of Agriculture and Food has issued an alert after diagnosis of EEE in a 11 year old horse in Simcoe county (other cases have been reported in this area in previous years as well). They say the horse is recovering, which is a bit of a surprise because mortality rates with EEE are very high, and most affected horses die quickly.

What does this mean for horses in Ontario?

Not a lot, since we know EEE crops up every fall, and there’s always some degree of risk, but it’s a good reminder that this disease is a concern particularly at this time of year. The risk here isn’t anywhere near the level it is in some US states, and with only a handful of cases every year (4 last year), the disease’s overall impact in Ontario is low. However, infection is typically fatal and therefore not something to be ignored. A vaccine against EEE is available for horses, and it’s been debated whether it should be a core vaccine for horses in Ontario. On one hand, the disease is typically deadly. On the other hand, it affects between 0 and a few horses every year, which is not many in the grand scheme of things (but if it’s your horse, you don’t really care about the "grand scheme" at that point).

What does it mean for people in Ontario?

Despite the name, EEE can affect people too. It’s rare, but like in horses, it’s devastating. There has never been a confirmed human case in the province, but they do happen  Earlier this month an elderly woman in Norfolk County, Massachusetts was diagnosed with and died from EEE (like Ontario, Massachusetts typically sees a few cases in horses every year as well). Humans and horses get infected the same way (a bite from an infected mosquito), so cases in horses mean there is EEE in mosquitoes in the area. There’s no vaccine for people, so we’re left with mosquito avoidance.

This is one of those "pay attention but don’t panic" diseases.