Equine Encephalitis (EEE/WEE/VEE)

Infection causes non-specific clinical signs and often affects the central nervous system.

• Fever
• Severe depression “sleeping sickness”
• Behavior changes
• Impaired vision
• Circling or head pressing
• Muscle twitches
• Inability to swallow
• Paralysis
• Convulsions, Death

1. Contact your veterinarian immediately.
2. Monitor other horses on the property for similar symptoms.

• Fast Facts: Equine Encephalitis

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• AAEP Core Vaccination Guidelines Eastern Western

EEE/WEE/VEE are transmitted only by the bite of infected mosquitoes; direct transmission between horses and people does not occur.  However, should an incursion of VEE occur, equine infections do present some risk to people.

Treatment consists of supportive care.  Survival rates for horses infected with EEE or VEE is low; however, WEE survival can be as high as 70-80%.

EEE/WEE/VEE vaccination is very effective at preventing clinical disease.  Vaccination needs to be repeated at minimum on an annual basis.  Consult with your veterinarian regarding boosters if you live or are travelling to an area with year round mosquito populations or an area that has previously reported cases of EEE/WEE. As VEE has not occurred in the U.S. for over 40 years vaccination is not recommended unless the animal will be travelling to endemic areas.

Reduce your horse’s exposure to mosquitoes:  eliminate any standing water (mosquito habitat) and place fans inside where the horses rest, limit outdoor activities at dawn and dusk, and use equine approved mosquito repellent.

• • 2020 Reported Equine Cases of Eastern Equine Encephalitis 

Annual Summary Reports 2006-2019.
Number of confirmed eastern equine encephalitis cases by State and County

• • 2019 Summary of Eastern Equine Encephalitis Cases in the United States
  • 2018 Summary of Eastern Equine Encephalitis Cases in the United States
    
  • 2017 Summary of Eastern Equine Encephalitis Cases in the United States
    
  • 2016 Summary of Eastern Equine Encephalitis Cases in the United States
    
  • 2015 Summary of Eastern Equine Encephalitis Cases in the United States
    
  • 2014 Summary of Eastern Equine Encephalitis Cases in the United States
  • 2013 Summary of Eastern Equine Encephalitis Cases in the United States
  • 2012 Summary of Eastern Equine Encephalitis Cases in the United States
  • 2011 Summary of Eastern Equine Encephalitis Cases in the United States
  • 2010 Summary of Eastern Equine Encephalitis Cases in the United States
  • 2009 Summary of Eastern Equine Encephalitis Cases in the United States
  • 2008 Summary of Eastern Equine Encephalitis Cases in the United States
  • 2007 Summary of Eastern Equine Encephalitis Cases in the United States
  • 2006 Summary of Eastern Equine Encephalitis Cases in the United States 
     
• State web sites with equine eastern or western equine encephalitis case reports
   
• USGS Eastern and Western Equine Encephalitis Maps - USGS Disease Maps Web site, produced in cooperation with CDC and ArboNET, includes current and historic maps of veterinary, human, bird, sentinel, and mosquito EEE and WEE cases by state and county. Veterinary maps on this site include data for several animal species in addition to horses (e.g., dogs, rodents).
   
• Case Definitions:
  • Eastern Equine Encephalitis Case Definiition
  • Western Equine Encephalitis Case Definition

Surveillance Information

Reports of equine cases of arboviral (i.e., arthropod-borne virus) diseases, including eastern and western equine encephalitis, are reported to ArboNet, an electronic-based surveillance and reporting system used to track and report arboviral activity. ArboNet captures laboratory-confirmed positive cases in humans, horses, other mammals, birds and mosquitoes across the United States. Equine case-finding varies by State, but primarily relies on passive reporting from private practitioners and diagnostic submissions. In some States, reporting is mandatory.