If I was reincarnated as a mosquito, I’d want to live where I do now (convenient, eh?). I live in the country surrounded by areas of "protected wetland," which, in many cases, is a fancy word for swamp. I try to avoid mosquitoes, but getting bitten is a regular (daily) event. As I was getting swarmed last night, I was thinking that the mosquito-borne disease I’m really concerned about is Eastern equine encephalitis (EEE). While quite rare in Ontario, with only a handful or no cases in horses every year, it’s a worry because it’s almost always fatal. It also affects people, not via transmission from horses but from being bitten by mosquitoes that pick up the virus from birds. It’s very rare in people, but it’s highly fatal.
This is the time of year that we start seeing mosquito-borne infections in Ontario, and a Disease Alert from the province re-inforces concerns about EEE. The alert was issued in response to a case of EEE in a horse in New York state, not far from the Canadian border. The horse, from the Ogdensburg, NY area, showed signs of illness on July 23 and died the next day (a pretty typical progression for this disease). Since mosquitoes don’t respect borders, cases in this neighbouring region suggest that infected mosquitoes might also be active in Ontario.
EEE isn’t the only mosquito-borne virus that we worry about – West Nile virus being the other main issue around here – so mosquito control and avoidance are important. While you can never guarantee that you or your animal will not encounter a mosquito, various things can be done to reduce mosquito numbers (e.g. eliminating sites of standing water (which are mosquito breeding sites) wherever possible… swamps being a logical exception) and to reduce the risk of being bitten (e.g. avoiding high risk areas and times, long clothing, mosquito repellants). Vaccines are available for EEE and West Nile virus in horses (but not people), and the risk of these diseases should be considered when designing a horse’s vaccination program.