A mosquito-borne brain fever: Let's learn about Western Equine Encephalitis!

As Sri Lankans, when we think of mosquito-borne diseases, dengue immediately comes to our mind, right? But like dengue, there are other diseases in the world that are transmitted by mosquitoes, but can be a little more dangerous, and that affect the brain. Today we are going to talk about one such disease. Its name is Western Equine Encephalitis. Although this is not common in our country, it is very important to be aware of such things.

What is Western Equine Encephalitis?

Simply put, it's a viral disease that's spread by mosquito bites. To be precise, it's a disease that belongs to the "arboviral" group. That is, it's a viral disease that's spread by arthropods like mosquitoes and fleas. The virus that causes it is very similar to two other dangerous types of brain fever, Eastern Equine Encephalitis and Venezuelan Equine Encephalitis viruses.

This disease can affect both humans and horses . The disease is transmitted by an infected mosquito. The main mosquito species responsible for this is (Culex tarsalis). However, the mosquito species (Aedes) and (Culiseta), which are known to spread dengue, can also transmit this virus.

The natural cycle of this virus is between birds and mosquitoes. That is, a mosquito bites an infected bird, which then bites a healthy bird and spreads the disease. Humans and horses are only accidental hosts in this cycle. That is, we do not get the disease directly from a bird. However, very rarely, the disease can be transmitted from a pregnant mother to her child through the placenta. This is not a respiratory disease.

Who is at greater risk?

• If you live in an area where this disease is common (especially the western and central states of the United States).
• If you are traveling to an area like that.
• If you spend a lot of time outdoors.

What are the symptoms of this disease?

Symptoms usually begin to appear between 5 and 15 days after being bitten by an infected mosquito. Symptoms initially resemble those of a common cold.

Most of the time, these common symptoms will go away and the disease will be cured. However, sometimes the condition can be more serious. Imagine, what would happen if this virus spread rapidly in our blood, crossed the natural barrier that protects the brain (blood-brain barrier) and entered the brain itself?

That's when the disease becomes dangerous. When the virus enters the brain, it can cause conditions called encephalitis , which is swelling of the brain tissue, and meningitis, which is inflammation of the membranes covering the brain .

When the nervous system is affected in this way, the following symptoms may occur:

• Dizziness
• Inability to look at bright light (photophobia)
• Dementia and disruptive behavior
• Excessive sleepiness
• Complete loss of consciousness (coma)
• Muscle stiffness and spasms (spasticity)
• Seizures
• Long-term effects such as learning disabilities

Young children and the elderly are most at risk for these neurological complications . The mortality rate from this disease is between 3% and 7%. In addition, between 15% and 30% of those who recover from the disease may develop long-term neurological damage.

How is the disease diagnosed and treated?

If you have traveled to an area where this disease is common and you develop the above symptoms, see your doctor immediately . The symptoms of this disease are similar to other types of viral meningitis, so diagnosis can be a bit challenging.

If the doctor suspects that your nervous system has been affected, you may be hospitalized and have several tests performed.

• Lumbar puncture: To examine the fluid in the brain and spinal cord (CSF).
• A CT scan is a test.
• An MRI scan is a test.
• Antibody tests: Although these can confirm the disease with certainty, the results can take several weeks to come back.

There are no specific antiviral drugs for this disease yet. Therefore, treatment is supportive . That is, doctors give medication to control symptoms such as fever and pain. If the nervous system is severely affected, treatment in an intensive care unit (ICU) may be necessary. This includes mechanical ventilation, controlling seizures, maintaining body fluid levels, and controlling very dangerous conditions such as increased intracranial pressure.

How can you protect yourself from this disease?

There is a good vaccine to protect horses from this disease. Although a vaccine has been developed for humans, it is not widely available for clinical use. It is only used in high-risk individuals, such as laboratory workers.

So, the best thing we can do is to protect ourselves from mosquitoes as much as possible . These tips are equally important for us to protect ourselves from dengue.