Japanese Encephalitis - Causes, Symptoms, Diagnosis, Treatment and Prevention

Introduction:

One of the leading viral encephalitis in Asia is Japanese encephalitis which occurs due to mosquitoes. It can be transmitted to humans via the bite of a mosquito carrying the virus. The transmission from one person to another person is not possible. Japanese encephalitis virus (JEV) is associated with viruses that cause St. Louis encephalitis and Murray Valley encephalitis, dengue fever, yellow fever, etc. The first case of JE was reported in Japan in 1871.

Encephalitis is a clinical condition characterized by the inflammation of the brain that leads to fear, confusion, headache, seizures, and may even cause death in some cases. Symptoms are seen to develop in fewer than one percent of people. The World Health Organization reports that almost 30 % of people who develop symptoms can face death. According to various researchers, the count of fatalities due to this condition is around 13,600 to 20,400 in a year.

Which Virus Causes Japanese Encephalitis?

The virus of JE belongs to the flavivirus family. The mosquito that passes it on is the Culex mosquito. The virus is known to infect horses, pigs, and humans. The virus can lead to miscarriages in pigs and encephalitis in horses.

How Is Japanese Encephalitis Transmitted?

Mosquitoes obtain the virus from feeding on birds that are infected with this virus. Then, these mosquitoes pass on these viruses to human beings and animals. Birds and other animals are not capable of transmitting this infection directly to humans. Only the infected mosquitoes are capable of doing so. The mosquitoes are mainly found in rural areas and agricultural lands. The larvae of mosquitoes breed in the water pools like in flooded rice fields.

What Are the Carriers and Vectors of Japanese Encephalitis?

A host is the one who acts as the source of the virus and the vector helps in transmitting the virus. According to studies, wild birds can be attributed to being the natural hosts for JEV and the vectors are the mosquitoes. It is to be noted that the vectors do not cause the disease as such but act as the transmitter of the disease alone.

When an animal is infected by the mosquitoes, it becomes a carrier and when other mosquitoes try to feed on the infected animals, they carry on to infect other animals. People in rural areas are at higher risk of developing this condition. Children are known to be more affected as the adults in the endemic area develop immunity with time.

What Are the Commonly Affected Geographic Locations of Japanese Encephalitis?

JE is very commonly seen in Southeast Asia. Various countries like China, Japan, Korea, Thailand, etc., have faced outbreaks but the disease has been controlled via vaccination. Occasionally, epidemics can be seen in countries like India, Malaysia, Myanmar, Nepal, etc. The US and northern Australia have reported a few cases.

What Are the Symptoms of Japanese Encephalitis?

People affected by Japanese encephalitis do not show symptoms but in case they develop symptoms, it happens within 5 to 15 days after they get infected. It can be mild or severe. The mild symptoms usually include fever with a headache but severe cases develop serious symptoms very fast.

The following are the symptoms that can be witnessed:

1. High fever.

2. Tremors.

3. Nausea.

4. Vomiting.

5. Headache.

6. Stiffness in the neck.

7. Spastic paralysis.

There may be changes in the brain functioning and these may be as follows:

1. Disorientation.

2. Stupor.

3. Coma.

4. Children may develop convulsions.

The swelling of testicles and the lower limb or leg is also seen.

When the individual develops brain symptoms, the effect can be lifelong and include hearing loss, difficulty in controlling emotions, and body weakness on one side. The survival rate varies among different age groups but children are more prone to fatality.

How Can Japanese Encephalitis Be Diagnosed?

Initially, when you visit your physician, you will be asked questions about your personal and medical history followed by the symptoms you are facing. Then, questions will be asked about your stay and visited places. After that, certain physical examinations may be done and you will be asked to get some laboratory and imaging tests done like CT (computed tomography), MRI (magnetic resonance imaging) of the brain.

A lumbar puncture may be done to obtain spinal fluid to check CSF (cerebrospinal fluid) for the exact type of virus causing the encephalitis. Human antibodies can be detected using immunofluorescence tests. Certain blood tests can also be performed.

What Are the Treatment Options Available for Japanese Encephalitis?

According to studies and research, no treatment or cure is available till now for JE. Only symptomatic treatment is possible. Antiviral drugs can be prescribed. The best way is to prevent the disease. Patients who survive the condition develop lifelong immunity.

How Can Japanese Encephalitis be Prevented?

The main mode of prevention is vaccination and also, insect repellent can be used.

Vaccination:

The vaccination for JE is given over two doses. The duration between the first and second dose is 28 days. Another way of giving vaccination is in an accelerated schedule where there is only a seven days difference between the two doses. But, the accelerated schedule is indicated in people between 18 to 65 years of age. Some symptoms may be seen post-injection of the JE vaccine which may be as follows:

1. Headache.

2. Pain in the muscles.

3. The site of injection can be red, sore, and swollen.

4. Hives and difficulty in breathing can happen but in rare instances.

DEET Insect Repellants:

These insect repellants can also be used to prevent mosquito bites and even loose-fitting clothing can prove to be beneficial.

Conclusion:

Japanese encephalitis is a viral infection that may affect the brain and certain other parts of the body and ultimately, affect the quality of life. Certain complications can be there for lifelong and hence, it is advisable to consult your physician as soon as possible when you experience some symptoms or are planning to visit or return from an affected geographic location. With the help of online platforms, it has become very easy to consult a physician or specialist at the ease of home. Hence, consult a physician to get more details about the same.