Cautions with EEE
Eastern Equine Encephalitis, called EEE for short, is a serious disease of horses and humans and, on occasion, llamas. Through mid-September 2009, there have been 14 horses, 2 pheasant flocks and a couple of llamas that have died due to EEE.
The virus that causes the disease is transmitted by mosquitoes. In Maine, we have a couple species of mosquitoes that are almost exclusively bird feeders. These mosquitoes feed on the blood of several different birds and in this process they ingest virus-infected blood from one bird (especially songbirds) and bite another bird transferring the virus to it. This keeps the virus in the bird population and this population now becomes the reservoir host for the disease. Another group of mosquitoes, collectively called bridge vectors, are a group of 4-6 species that feed on both birds and mammals. These mosquitoes bite an infected bird and pick up the virus. Later they bite a horse or human and the virus is transmitted to the new host. Unfortunately, in these hosts it can kill almost 100% of horses and about 30% of humans. About 50% of the humans that recover have some type of neurological problem that may remain with them for the rest of their lives. Horses and humans are both considered dead end hosts, which means they don’t carry enough virus in their blood to infect a mosquito that may feed on them, therefore, breaking the cycle.
At this time of year (Sept-Oct), the best way to protect your from mosquitoes is personal protection. Try to limit outside activity between 1-hour before sunset until 1-hour after sunrise (the time when most species of mosquitoes are active, especially if the temperature is above 50 degrees. When outside, cover up-- wear long sleeve shirts and pants and use a CDC approved and recommended repellent, such as DEET (Chemical Name: N,N-diethyl-m-toluamide or N,N-diethly-3-methyl-benzamide); Picaridin (KBR 3023, Chemical Name: 2-(2-hydroxyethyl)-1-piperidinecarboxylic acid 1-methylpropyl ester ); Oil of Lemon Eucalyptus* or PMD (Chemical Name: para-Menthane-3,8-diol)the synthesized version of oil of lemon eucalyptus IR3535 (Chemical Name: 3-[N-Butyl-N-acetyl]-aminopropionic acid, ethyl ester).
While there is no vaccination for humans there is one for horses and other equines and so this disease is preventable by routine vaccination. Many are available, and often can be purchased at feed or pet stores for owner administration to their own horses. Often EEE vaccination can be given in combination with Tetanus, another important equine vaccination. This makes it a very available, affordable option. Generally, vaccination for EEE is carried out annually but horse owners should consult with their practicing veterinarian to decide whether a booster is needed now, due to the current increased risk.
Source: September 23, 2009 email from Jim Dill, Pest Management Specialist and Lichtenwalner, A. & D. Hoenig, Eastern Equine Encephalitis Virus in Maine 2009: Frequently Asked Questions, 2009 http://www.umext.maine.edu/maineequine/EEEFAQ09.htm , accessed Sept. 2009.
