Summary about Disease
Western equine encephalitis (WEE) is a mosquito-borne viral disease that can cause inflammation of the brain. It primarily affects horses but can also infect humans, particularly children and the elderly. The disease is caused by the Western equine encephalitis virus (WEEV). While many infections are mild or asymptomatic, severe cases can lead to neurological damage and even death.
Symptoms
Symptoms in humans can range from mild, flu-like illness to severe neurological issues.
Mild cases: Fever, headache, muscle aches, fatigue.
Severe cases: High fever, stiff neck, disorientation, seizures, coma, paralysis, permanent neurological damage.
Causes
WEE is caused by the Western equine encephalitis virus (WEEV). The virus is primarily transmitted to horses and humans through the bite of infected mosquitoes. Mosquitoes become infected by feeding on infected birds, which serve as the natural reservoir for the virus.
Medicine Used
There is no specific antiviral treatment for WEE. Treatment focuses on supportive care to manage symptoms and prevent complications. This may include:
Hospitalization
Respiratory support (if needed)
Intravenous fluids
Medications to control fever and seizures
Physical therapy to help regain lost function
Is Communicable
WEE is not directly communicable from person to person or from horses to humans. Transmission occurs solely through the bite of an infected mosquito.
Precautions
Precautions to prevent WEE infection involve reducing exposure to mosquitoes:
Use insect repellent containing DEET, picaridin, IR3535, oil of lemon eucalyptus (OLE), para-menthane-diol (PMD), or 2-undecanone.
Wear long sleeves and pants when outdoors.
Avoid being outdoors during peak mosquito activity (dawn and dusk).
Ensure window and door screens are intact.
Eliminate standing water around homes (e.g., in tires, flower pots, bird baths) to prevent mosquito breeding.
Vaccinate horses against WEEV.
How long does an outbreak last?
The duration of a WEE outbreak can vary depending on several factors, including mosquito populations, environmental conditions (temperature and rainfall), and the presence of infected bird reservoirs. Outbreaks typically occur during the summer and early fall months, when mosquito activity is highest. They usually subside with the onset of cooler temperatures and the decline in mosquito populations. An outbreak might last for several weeks to a few months.
How is it diagnosed?
WEE is diagnosed through laboratory testing of blood or cerebrospinal fluid (CSF). Tests used include:
Serological tests: To detect antibodies against WEEV in the blood. IgM antibody capture ELISA (MAC-ELISA) is commonly used.
Reverse transcriptase polymerase chain reaction (RT-PCR): To detect the virus's genetic material in blood or CSF.
Plaque reduction neutralization test (PRNT): To confirm the presence of neutralizing antibodies.
Timeline of Symptoms
The incubation period (time between mosquito bite and symptom onset) for WEE is typically 2 to 10 days.
Early symptoms (2-10 days after bite): Fever, headache, muscle aches, fatigue.
Severe symptoms (if they develop): Usually appear within a few days of the initial symptoms. These include high fever, stiff neck, disorientation, seizures, coma, and paralysis.
Recovery: Recovery from mild cases usually occurs within a few weeks. Severe cases may have long-term neurological complications requiring months or years of rehabilitation, or may result in permanent disabilities.
Important Considerations
WEE is a serious but relatively rare disease.
Early diagnosis and supportive care are crucial for improving outcomes in severe cases.
Vaccination of horses is an important preventive measure.
Public health surveillance is essential for monitoring mosquito populations, virus activity, and human and animal cases to implement appropriate control measures.