Eastern Equine Encephalitis Kills Emus in Ontario
Eastern equine encephalitis (EEE) was recently identified as the cause of an outbreak of disease in emus on a farm near Brockville, Ontario. EEE is a viral disease that is spread by mosquitoes, and can cause severe neurological disease in horses. Previous equIDblog posts describe EEE in more detail.
Emus are quite susceptible to EEE. Although EEE cannot be transmitted fro emus to horses, the relevance of this report to horse owners is that the emu outbreak indicates that the virus is present in mosquitoes in that region.
Most of the emu deaths in this outbreak occurred in mid-October. It is unclear whether there is any further risk to horses, people or other animal species. Being a mosquito-borne disease, EEE transmission should decrease dramatically after the first few hard frosts in the fall. It is unlikely that there is a significant risk of further EEE transmission in the Brockville area this year.
Vaccination of horses in Ontario at this time of year is probably not useful because of the low risk of mosquito transmission and the time required for immunity to develop after vaccination. However, people should consider the risk of exposure in subsequent years, and try to reduce this risk. This can be done through a combination of avoiding and controlling mosquitoes (which are also important for prevention of West Nile virus infection) and vaccination against EEE. Since EEE is so rare in Ontario, it is not typically considered a "core" vaccine in horses. However, vaccination for EEE should be considered in regions where the disease has previously been identified.
