Western equine encephalomyelitis

Western equine encephalomyelitis (WEE) is a disease caused by the Western equine encephalitis virus, an Alphavirus in the family Togaviridae. This virus is transmitted by mosquitoes, primarily the Culex species, and is found in regions of North America. It primarily affects horses and humans and can lead to severe neurological disease and even death in these hosts.

Transmission

The Western equine encephalitis virus is maintained in a cycle between mosquitoes and birds. Mosquitoes, particularly the Culex tarsalis, become infected by feeding on birds that carry the virus. These infected mosquitoes can then transmit the virus to other hosts, including horses and humans. Transmission to humans is considered incidental and typically occurs in rural or semi-rural areas where mosquito populations are dense and where these insects have opportunities to feed on both avian and mammalian hosts.

Symptoms

In humans, the symptoms of WEE can range from mild flu-like symptoms to severe neurological impairments. The onset of the disease typically begins with fever, headache, nausea, vomiting, and tiredness. More severe cases can progress to confusion, seizures, and coma, which can be fatal.

In horses, WEE can cause a range of symptoms including fever, depression, anorexia, and neurological issues such as unsteady gait, hyperexcitability, or paralysis.

Prevention and Control

Prevention of WEE primarily involves controlling mosquito populations and limiting exposure to mosquito bites. This can be achieved through the use of mosquito repellents, maintaining screens on windows and doors to prevent mosquito entry, and eliminating standing water where mosquitoes breed.

Vaccines are available for horses to protect against WEE, but there is currently no vaccine available for humans. Public health surveillance and rapid response to mosquito-borne disease outbreaks are crucial in preventing widespread transmission.

Epidemiology

WEE was first isolated in California in 1930. Since then, outbreaks have been reported in various parts of the United States and Canada, particularly in the western and central regions. The incidence of WEE in humans has decreased significantly due to effective mosquito control measures and public health interventions.

See Also

• Eastern equine encephalomyelitis
• Venezuelan equine encephalomyelitis
• Encephalitis