EEE in Nova Scotia
A Nova Scotia horse has died of eastern equine encephalitis (EEE). EEE is a rare disease in Canada, but it is sporadically identified in some provinces. It was reported that this is the "first case" in Nova Scotia, although it wasn't clear if they meant in 2009 or ever.
EEE is a highly fatal mosquito-borne viral disease of horses. There is no specific treatment. The virus can also affect (and kill) people, but horses cannot transmit the infection to people - horses and people (and some other species) are infected by being bitten by infected mosquitoes.
The veterinary clinic that diagnosed the case reported that 120 doses of EEE vaccine will be delivered there this week. A ProMed moderator commented that he/she hoped a major vaccination campaign will be started. However, it's far from certain that any vaccination efforts will be effective, particularly for this season. EEE is a very sporadic disease in Canada, but since it's so severe, vaccination certainly should be considered. However, considering most horses in Nova Scotia have never been vaccinated previously for EEE, it will likely take a couple of doses and several weeks before adequate antibody levels are present. By that time, the risk of exposure may be even lower because the mosquito season is ending in the maritimes. I'm definitely not saying don't vaccinate, however, because of the short remaining mosquito season and the lag time from vaccination to effective immunity, the immediate focus should really be on mosquito avoidance.
Deciding whether or not to vaccinate against EEE in areas where it is very rare and sporadic can be tough. From a population standpoint, it's somewhat difficult to recommend vaccinating all horses against a disease that may only affect a handful or horses, if any. However, from an individual horse standpoint, it's bad news if you happen to be that rare horse that gets infected. Really, it comes down to risk aversity and economics, and it's up to each horse owner (in consultation with their veterinarian) to determine what diseases they should vaccinate against.
