Encephalitis

While the West Nile virus can result in cases of encephalitis, it is not the only mosquito borne type of encephalic disease; there are several others, some of which are actually more severe. The more common ones are as follows.

Eastern Equine Encephalitis

As its name implies, this viral infection is found primarily in the Eastern United States. It is a disease that affects both horses and humans. It is transmitted through the bite of a mosquito that has fed on an infected bird. The most frequent species that transmits the disease is the Culiseta melanura.

Far more than West Nile virus, it is one of the more serious of the mosquito borne encephalitic diseases. The symptoms, in their mild form, are like a mild case of the flu. At the other end of the spectrum, it produces encephalitis, or inflammation of the brain, coma and death. It has an alarmingly high mortality rate: 35% of those who contract it die. Of those who survive an infection, about 35% have some residual neurological damage, ranging from mild to severe.

These precautions are not to be taken lightly, even though the disease is not common, it is one of the most serious of mosquito borne diseases.

Luckily, it is quite rare. From 1964 to the present, only 200 cases have been confirmed in the United States. The states with the highest rates of cases are on the Eastern seaboard, ranging from Florida to Massachusetts. Part of the reason for its rare occurrence is that carrier mosquitoes that inhabit swamps, which humans do not frequent often.

The greatest risk of danger is among those over 50 and less than 15 years of age who visit, live or work in areas where the mosquitoes are prevalent. The best way to avoid infection is to avoid being bitten. So, stay away from swampy, marshy areas, if you live on or visit the East coast. And, follow the usual precautions about wearing protective clothing, staying inside during feeding times, and always wear a good repellant. Unfortunately, there is no vaccine for humans, although there is one available for horses.

Japanese Encephalitis

This viral infection is transmitted by mosquitoes breeding in rice paddies in Asia, mostly from one of the Culex species. It is closely related to the virus that causes St. Louis encephalitis. In this case, the mosquitoes feed on infected domestic pigs and birds, which then feed on human hosts. Like the West Nile virus, many people have no symptoms. The milder forms of infection can produce some fever and headaches. The more severe symptoms include high fever, headache, disorientation, coma, neck stiffness, convulsions, stupor, and paralysis.

The symptoms usually manifest in one to two weeks after the bite. Its reported mortality rate is very broad, somewhere between .3% to 60%.

This is the leading cause of viral based encephalitis in Asia, but rarely occurs outside of that area.

Like the other forms of mosquito borne viral encephalitis, there is no treatment, except to alleviate the symptoms. It is much more common in rural areas of Asia, and is rarely found in urban areas.

Again, the best precaution is to avoid being bitten, and to take action to avoid areas of exposure.

Lacrosse Encephalitis

This is one of the more rare forms of mosquito viral encephalitis diseases. And, fatalities are very rare. More often, mild symptoms are the norm. There are only about 70 cases reported each year, and less than 1% of those result in fatality. It is transmitted mostly by one of the Aedes triseriatus , the treehole mosquito, that is found primarily in wooded habitats. The animal hosts for Lacrosse encephalitis are mostly chipmunks and squirrels. Treehole mosquitoes breed in small collections of water, like crevices in trees, discarded cans and low-lying puddles.

As with all other types of encephalitis diseases, prevention is the best cure. Avoid going into the mosquito’s natural habitat, wear protective clothing, and use a good repellant.

St. Louis Encephalitis

This virus is very closely related to Japanese encephalitis, but far less prevalent. Mostly, its victims have only a mild illness, although it can produce the more severe symptoms.

It occurs with varying frequency, often rarely, but sometimes up to 3000 cases per year. It is spread by various members of the Culex species.

Western Equine Encephalitis

This version of mosquito borne virus is really not at all common. There have been only about 600 reported cases since 1964, and its symptoms are like most encephalitic disorders, mild flu like symptoms to a few, rare deaths. It can be epidemic, but its occurrence is hard to predict. While related to the Eastern equine encephalitis virus, it is simply not as prevalent. There is no known treatment, except addressing symptoms, and the best precaution is avoidance. View a map of worldwide cases by type.

As you can see, mosquito borne encephalitic diseases encompass far more than just West Nile virus. And, the best means of combating them is to avoid the bites. The best way to avoid these types of illnesses comes from a double approach. Learn all you can about them, and then be smart about staying out of harm’s way. It is important to take a balanced view, too.

Sure, these are serious diseases, and not to be ignored, but at the same time, recognize that they are not really than common in urban dwelling environments.