Eastern/Western Equine Encephalomyelitis (EEE/WEE)
Eastern Equine Encephalomyelitis (EEE) and Western Equine Encephalomyelitis (WEE), sometimes called “sleeping sickness,” are caused by viruses that attack the brain and spinal cord. Birds and rodents are the primary reservoirs and the diseases are spread by mosquitos. Unvaccinated horses are particularly susceptible to EEE and WEE and often serve as sentinels of the diseases, which also affect humans. EEE is more common than WEE and is found widely in several regions of the United States, especially in areas with high mosquito populations.
Merck Animal Health Solutions
PRESTIGE flu-containing equine vaccines contain the most updated flu strains available.
For vaccination of healthy horses 6 months of age or older, as an aid in the prevention of disease caused by Eastern and Western encephalomyelitis viruses and tetanus, as an aid in the control of respiratory disease caused by EIV, Equine Herpesvirus types 1 and 4 (EHV-1 and EHV· 4), and as an aid in reduction of virus shedding of EIV and EHV-1. Duration of immunity(D01) has been shown to be at least six months for EIV.
For vaccination of healthy horses 6 months of age or older, as an aid in the prevention of disease caused by Eastern, Western and Venezuelan encephalomyelitis viruses and tetanus and as an aid in the control of respiratory disease and as an aid in the reduction of virus shedding caused by Equine Influenza Virus (EIV). Duration of immunity (DOI) has been shown to be at least six months for EIV.
An effective vaccine for Eastern and Western encephalomyelitis, tetanus and West Nile virus in horses.
For vaccination of healthy horses 6 months of age or older, as an aid in the prevention of disease caused by Eastern, Western and Venezuelan encephalomyelitis viruses and tetanus.
Transmission Parasite Life Cycle
EEE and WEE are transmitted only by the bite of infected mosquitoes; direct transmission between horses and people does not occur.
Infection affects the central nervous system.
- Moderate to high fever (>101.5)
- Severe depression
- Lack of appetite
- Behavior changes
- Impaired vision
- Circling or head pressing
- Muscle twitches
- Inability to swallow
- Weakness, incoordination
- Paralysis of one or more limbs
- Inability to stand
- Convulsions, death
- High mosquito population
- Standing water
- Vaccination is recommended as a core protection strategy
“Eastern & Western Equine Encephalomyelitis,” American Association of Equine Practitioners, copyright 2020, aaep.org/guidelines/vaccination-guidelines/core-vaccination-guidelines/easternwestern-equine-encephalomyelitis.
“Equine Encephalitis (EEE/WEE/VEE),” USDA Animal and Plant Health Inspection Service, Dec. 29, 2020, www.aphis.usda.gov/aphis/ourfocus/animalhealth/animal-disease-information/equine/eee-wee-vee/equine-encephalitis.
“Eastern Equine Encephalitis (EEE),” Equine Disease Communication Center: Disease Fact Sheet, EDCC and AAEP, 2017, aaep.org/sites/default/files/Documents/Outside%20Linked%20Documents/DiseaseFactsheet_EEE%20Cobranded.pdf.
“Western Equine Encephalitis (WEE),” Equine Disease Communication Center: Disease Fact Sheet, EDCC and AAEP, 2017, https://aaep.org/sites/default/files/Documents/Outside%20Linked%20Documents/DiseaseFactsheet_WEE_FINAL%20Cobranded.pdf