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Encephalitis and Mosquitoes

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Every year, millions of people die from mosquito-borne diseases. Many people receive severe skin irritations and even allergic reactions from mosquito bites and their saliva. Mosquitoes are the principal carriers of different types of encephalitis that are extremely harmful to humans and animals.

Individuals who have been bitten by an infected mosquito will have symptoms appearing five to 15 days after the bite. Medical attention should be sought if any two of the following symptoms appear:

  • Fever above 103 degrees F
  • Severe headaches that do not go away
  • Blurred vision, tremors, disorientation, muscle aches, pain or neurological ticks
  • Vomiting or nausea

EEE – Eastern Equine Encephalitis

Infected mosquitoes spread Eastern Equine Encephalitis to horses and humans. It is one of the most serious of all encephalitis viruses because it attacks the central nervous system. Once the virus has affected the nervous system, it can cause acute health problems and even death. EEE is found in South, North and Central America as well as in the Caribbean.

EE encephalitis has a difficult cycle of life. It starts with infected birds that the mosquitoes feed on, and then the mosquitoes become infected and are carriers of the disease. The mosquitoes then transfer the encephalitis when they bite horses, humans and other mammals. After being bitten by an infected mosquito, a human may have mild flu symptoms, fever, sore throat and a headache.

More severe cases would affect the central nervous system, create a sudden high fever, extreme headache, and quickly lead to seizures and coma. Encephalitis can cause brain damage quickly. Half of the patients with severe Eastern Equine Encephalitis die, and those that do survive may need lifetime care. There is no vaccine available for humans, but there is one available for horses.

SLE – St. Louis Encephalitis

St. Louis Encephalitis is also transmitted through infected birds to man and other animals. It is found throughout the United States, most commonly along the Gulf of Mexico. Florida has seen several epidemics of St. Louis Encephalitis.

The very young and the elderly are more susceptible then those people between the ages of 20 and 50 years old. More than 4,000 cases of confirmed St. Louis Encephalitis were reported in the United States in the years 1964-1998. The symptoms are much the same as in EEE and there is no vaccine for humans. The last fatal case of SLE was reported in 2003 in Louisiana.

LAC – LaCrosse Encephalitis

LaCrosse Encephalitis is not as common as EEE or SLE and occurs only in the states east of the Mississippi. It is more prevalent in the Appalachian region. LaCrosse, Wisconsin first reported a woodland mosquito as the carrier that infected small mammals and humans. Children younger than 16 are usually affected and no is vaccine available.

WEE – Western Equine Encephalitis

California recognized the first case of WEE in 1930 when it showed up in a horse. It is usually found west of the Mississippi, parts of Mexico and Canada. Birds and small mammals are the typical hosts for this type of encephalitis. Mosquitoes carry the disease to humans and other animals. Three cases have affected chicken flocks in Arizona, but no human cases have been reported since 1964. There is no vaccine for humans, but there is one for horses.

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