DISEASE PROFILE
EasternEquine Encephalomyelitis:
Disease Name:Eastern-Equine-Encephalomyelitis
Species Affected:Equidae
About the Disease:
Eastern-Equine-Encephalomyelitis is a rare but serious mosquito-borne viral disease
thataffects humans, horses and some birds. The disease is transmitted to people and horses
through the bite of an infected mosquito.After infection equines may suddenly die or show
progressive central nervous system disorders.Horses and human are often referred to as
"dead-end" hosts for Eastern -Equine-Encephalomyelitis. This disease is an OIE
Reportable Disease as in the Disease Category 4.This disease is also known as Eastern
Equine Encephalitisand ismost commonly occurs in the Eastern United States and Canada.
Animals Affected: Horses, donkeys, mules and occasionally birds
Cause:
Eastern -Equine-Encephalomyelitis is caused by RNA virus belonging to the genus Alpha
virus of the family Togoviridae family. This virus is closely related to Western equine
encephalitis virus and Venezuelan equine encephalitis virus.This strain of virus is widespread
in Eastern part of America. This virus normally cycle in bird populations, and are transmitted
mainly by mosquitoesCuliseta melanurawhich appears to be the most important vector for
transmission of this virus.
Source of infection:
Wild birds that live in farming areas around irrigated fields are most often the source of
infection for this virus and birds are the usual reservoir hosts. The disease is transmitted when the
mosquito, Culiseta melanura bites an infected bird and then bites to a human or horse.
Infected humans and horses cannot spread the disease.Horses, humans and other mammals
are accidental dead-end hosts and are not usually a source of infection.
Symptoms:
The initial clinical signs include fever, anorexia and depression. In severe cases, this
prodromal stage is followed by encephalitis; altered mentation, hypersensitivity to stimuli,
involuntary muscle movements, impaired vision, aimless wandering, head pressing, circling,
an inability to swallow, ataxia, paresis, paralysis and convulsions may be seen. Periods of
excitement or intense pruritus can also occur. Laterally recumbent animals sometimes have a
characteristic “paddling” motion. In addition, some animals may develop diarrhea or
constipation, or have significant weight loss. Some affected horses die, particularly when
infected with Eastern -Equine-Encephalomyelitis, within a few days. Horses that recover
from encephalitis have a high incidence of residual deficits. Eastern -EquineEncephalomyelitiscause asymptomatic infections or mild disease without neurologic signs.
Eastern equine encephalomyelitis virus infections are asymptomatic in most species of birds,
but serious or fatal infections can occur in some species.
Control and Management:
1) Isolation and strict quarantine of newly brought animal in the herd.
2) Reducing vector population.
3) Isolation of infected horses.
4) Vaccination is the best preventative control for Venezuelan-Equine-Encephalomyelitis.
5) Good Stable hygiene is always recommended.
6) Movement of animal should be controlled
7) Strict decontamination of infected premises and
8) Insects biting and population should be reduced
Vaccines:
There is a vaccine available for horses. However, the vaccine is currently not available in
India.
Meteorological Occurrence:
Eastern equine encephalomyelitis virus exists primarily in the eastern and central parts of
North America, throughout Central America and the Caribbean, and in eastern parts of South
America.The outbreaks generally occur in late summer and fall as a consequence of
increasing numbers of mosquito vectors. The disease occursin some swampy areas nearly
every year during the warm months.
Prepared by:
Dr. Peter N
JRF, NADRS, Manipur.
Disease Investigatory Laboratory
Directorate of Veterinary, & A.H. Services,
Manipur