Travel Health Service Equine Encephalitis
Travel related diseases

Equine Encephalitis

What is Equine Encephalitis?

Equine Encephalitis is a rare viral mosquito-borne disease. Eastern Equine Encephalitis (EEE) is caused by eastern equine encephalitis virus, Western Equine Encephalitis (WEE) is caused by western equine encephalitis virus and Venezuelan Equine Encephalitis (VEE) is caused by Venezuelan equine encephalitis virus. Equine Encephalitis can affect the central nervous system and cause severe complication and death. Symptoms range from mild flu-like illness (like headache, fever, chills and vomiting) to frank encephalitis, coma and death. It is endemic in North, Central and South America.

Approximately a third of all people with EEE die from the disease. Of those who recover, many are left with disabling and progressive mental and physical sequelae. Case fatality of WEE is 3% and neurologic sequalae is seen in 5-30% of infected people and is more common in children. Fatalities are rare for VEE.

How does it spread?

Equine Encephalitis is transmitted to humans through the bite of an infected mosquito. The main EEE transmission cycle is between birds and mosquitoes. Several species of mosquitoes can become infected with EEE virus. WEE virus has a complex lifecycle involving birds and a specific type of mosquito, Culex tarsalis, that is common in farming areas and around irrigated fields. VEE has a zoonotic reservoir in bats, birds, rodents, horses, and donkeys.

People living in or visiting endemic areas and those who work outside or participate in outdoor recreational activities in endemic areas are at increased risk.

How can you prevent it?

At present, vaccine is only available for horses but not for human. Avoiding the bite of mosquito is the best defence against contracting the disease.. The personal protection measures against mosquito bites are as follows:-.

  • Wear long-sleeved shirts and trousers
  • Rest in air-conditioned or well-screened rooms;
  • Use aerosol insecticide indoor and use bed nets if sleeping areas are not air-conditioned or screened.
  • Use insect repellents containing DEET on exposed skin and clothings. For details about the use of insect repellents, please refer to Frequently Asked Questions.
  • If travelling in endemic rural areas, carry a portable bed net and apply permethrin on it as well as to clothes.

How is it treated?

Travellers returning from countries where the disease is endemic or an outbreak has occurred, and suffer from symptoms of the disease should seek prompt medical advice. Currently, there is no specific antiviral drug for Equine Encephalitis and treatment is mainly symptomatic.