It’s that time of year. Mosquitoes have been annoying me for months (I get bitten multiple times a day where I live, even with repellent), but now they’re becoming a bigger issue. While mosquitoes bite all season, some of the diseases they transmit are only a significant risk at certain times of year.

One high profile disease that is spread by mosquitoes is Eastern Equine Encephalitis (EEE). As you can guess by the name, the virus that causes EEE  affects horses, in which it causes severe and usually rapidly fatal neurological disease. EEE can also affect people (and rarely other species, like dogs). It’s a relatively rare disease even in horses, but when it occurs it’s devastating, so the risk should not be taken lightly.

Recently, two cases of EEE were confirmed in horses on separate farms in Haldimand County, Ontario. Both were euthanized. Three more potential (but untested) cases were also reported in the area. The two confirmed cases occurred at the end of July/beginning of August, which is pretty early in the season for EEE in Ontario.  Whether that’s simply yearly variation cases or a sign that things are more active this year is hard to say, but time will tell.

For horses:

EEE is a rare but nasty disease, and there are vaccines available to help prevent it. The cost-benefit of vaccination against very rare diseases can be debated, but given the severity of EEE, horse owners in areas where the virus is found should consider vaccinating.  But remember that horses need to be vaccinated before the virus starts circulating in the area in late summer and fall (so don’t wait until you hear about a case in your area, or you may be too late to protect your horse in the same season).

For people:

Horses cannot transmit the virus to people (or other animals). We get the virus the same way horses do, from the bite of an infected mosquito.  Surveillance in horse lets us know about viral activity in the area (i.e. the horses can act like disease sentinels for people). Regardless, the risk of EEE, West Nile virus and other mosquito-borne pathogens means we should all take basic precautions to reduce mosquito exposure, such as the use of DEET repelants, avoiding high risk areas at dusk and dawn (e.g. swampy areas) and removing standing water where mosquitoes breed whenever possible.

Hopefully there’s not more to come in terms of EEE in Ontario, but considering we usually only see a handful of cases a year, this year’s early August numbers are a concern.