Written by: Dr. Jacquie Jacob, University of Kentucky

Eastern equine encephalitis is a virus typically carried by infected mosquitoes. Birds (especially pheasants, chukar partridges, and emus), mammals (especially horses), and people can contract this virus. Birds are the major source of the virus.

The Culiseta melanura mosquito is the primary transmitter of the virus to poultry. Other mosquito species carry the disease too, but they feed mostly on other animals. Once a flock is infected, the disease can spread as birds cannibalize sick or dead members of the flock.


Affected birds show reduced feed consumption, staggering, and paralysis. Surviving birds may be blind and may have muscle paralysis and difficulty holding their heads up. Equine encephalitis affects the nervous system. Damage to a bird’s nervous system varies depending on the species. In pheasants, there is pronounced leg paralysis, twisting of the neck, and tremors. Mortality is usually high among these birds. Chukar partridges and turkeys show drowsiness, paralysis, weakness, and death.


There is no treatment available for this disease.


The best way to prevent this disease is to remove the source of the infection—mosquitoes. It is also possible to vaccinate birds, especially pheasants, with the vaccine prepared for horses. The recommended dose for a bird is one-tenth of the dose a horse would receive.