Equine Encephelitis in the Event of Disasters

Equine encephalitides are viral zoonoses that occur episodically and cause outbreaks in equines and, less frequently, in humans. The ethiological agents are viruses belonging to the genus Alphavirus in the Togaviridae family. Infection is maintained in natural foci between wild reservoirs anD mosquitoes.  Three viruses are important: Western equine (WEE), eastern equine (EEE) and Venezuelan equine encephalomyelitis (VEE).  A fourth member, Higlands J virus, occurs in the eastern United States, primarily in Florida.

In Central America, a growing activity of syndromes compatible with equine encephalitis has been observed in horses during the last three years, particularly in Belize, Guatemala,Honduras and Panama.  Laboratory isolations of the virus and/or serological typing have shown EEE and VEE viral infection. These two agents are known to cause high morbidity and mortality among horses, donkeys and mules that, in turn, become amplifiers of the infection that eventually spreads to human by mosquito bites.

The VEE virus has caused major epidemics in the Americas. In 1969, an  outbreak started in Ecuador and spread through Peru, Colombia,  Venezuela, Central America and Mexico reaching finally Texas in 1971.  Close to 50,000 equines died. In Ecuador, alone, 31,000 human cases were  reported and 310 deaths.

In 1995, an outbreak occurred in Venezuela and Colombia that affected  seven States in Venezuela and the Department of La Guajira in  Colombia. This outbreak registered more than 40,000 human cases and 46  deaths. The outbreak was associated with one period of unusually intense rain with a subsequent increase of mosquito populations, vectors of VEE  virus and the lack of vaccination among the equine population.

The current situation in Central America is similar:

  1. Immediate vaccination of horses mules, and donkeys.
  2. Detection and treatment of mosquito breeding sites, especially those close to permanent and temporary human settlements (refugees). 
  3. Equine case monitoring and reporting, characterized by: Fever, anorexia and depression accompanied by nervous signs such as: deep depression, difficulties with equilibrium, resting the head on objects, insomnia. Several animals might show hypersensitivity to touch and sound, excitation, walk in circles, blindness and bumping into obstacles. They often fall and are unable to get up. 
  4. Monitoring of probable human cases, characterized by: - fever headache, nausea, vomiting, muscular and pains in the joints, chills, photophobia and prostration, convulsions or alteration of the state of conscience, somnolence, hyperacusia and coma. - In people under three years of age: Fever, alterations of the state of conscience or convulsions.


For more information, you can consult the Manual "Bases for  Epidemiological Surveillance of Venezuelan equine encephalitis in the  Region of the Americas", which includes definition of concepts,  guidelines for the establishment and development of programs for  epidemiological surveillance and examples of formats for the  management of the information system during normal conditions and in  case of outbreaks or epidemics.

Contact:
Albino J. Belotto
Regional Advisor
Veterinary Public Health Program
División of Disease Prevention and Control
PAHO/WHO, Washington, D.C.
Tel: 202-974-3191
E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it