Eastern equine encephalitis (EEE) and western equine encephalitis (WEE) virus infections occur in horses and other equines in Louisiana. Eastern equine encephalitis (EEE) is more common and tends to occur in outbreak form. These diseases are transmitted to horses and humans by mosquitoes that have fed on infected wild birds. The EEE virus was first identified in mosquitoes in Louisiana in 1951 near Ponchatoula in Tangipahoa Parish. The virus is active in horses to some degree every year. EEE virus attacks the central nervous system of its host. Unvaccinated horses are particularly susceptible to the infection. The disease appears within five days after mosquitoes transmit the virus to the horse. Onsets of clinical signs of EEE are abrupt, and affected horses die within three days. Signs of EEE in horses include fever; a sleepy appearance ; some muscle twitches of the head, neck, shoulder and flank; and a weak, staggering gait. Affected animals are soon down, unable to stand. There is no effective treatment. The fatality rate is 90 percent or higher. An animal that survives may have permanent brain damage.
Where does EEE come from?
EEE occurs in nature in a wide variety of songbirds. Blood
samples from New Jersey birds, where most of the research on
EEE has been done, indicate that the blue jay, tufted
titmouse, chickadee, catbird and cardinal are most often
infected. Although these birds do not develop the disease,
they maintain high levels of the EEE virus. They are
considered reservoirs in the disease cycle.