Published: July 10, 2009 12:23 am      

Case is a reminder to be careful around mosquitoes

A case of Eastern Equine encephalitis, a mosquito-borne virus that can infect humans, has been found in a horse in Wayne County.

EEE is a dangerous disease that can cause severe brain damage, coma, and death and has a one-third mortality rate in humans, according to the U.S. Centers for Disease Control. It has an even higher mortality rate in horses, and the infected horse from Wayne County is now dead.

Fortunately, though the mortality rate of EEE is high, the infection rate is low, with an average of five human cases per year. There have been only approximately 220 confirmed cases of EEE in the U.S. between 1964 and 2004.

The virus is passed from birds to mosquitoes, who then pass it to humans and horses. Both humans and horses are considered "dead-end" carriers of the virus, meaning that, once infected, they do not pass the disease to other mosquitoes.

The discovery of EEE in a horse does not necessarily mean that the risk of humans contracting the virus is higher than it was in previous years, said Dr. Alison Moore of Seal-Laird Veterinary Hospital, because "the bird population is not carrying the virus any more in one year than any other year."

What the discovery does mean, though, is that mosquito season is in full swing. The Wayne County case is a reminder that mosquitoes are active, that they can make you sick, and that precautions should be taken to protect against EEE and other mosquito-borne illnesses such as West Nile Virus.

Dr. Moore's advice, "Be conscious of staying indoors or spraying if you have to go out."

Indeed, the best way to avoid mosquito-borne diseases is to avoid being bitten by mosquitoes in the first place.

The CDC recommends spraying with an effective mosquito repellent, staying indoors when mosquitoes are biting, wearing protective clothing, and getting rid of standing water to avoid being bitten by mosquitoes.

The Mississippi State Department of Health has identified two types of mosquito-borne illnesses found in Mississippi. The most common are West Nile Virus and St. Louis encephalitis. LaCrosse encephalitis and EEE are also found in Mississippi but are less prevalent.

According to the health department Web site, "very few human cases of EEE have ever occurred in Mississippi."

Still — that doesn't mean people should not heed the old warning "better safe than sorry." Taking a few simple measures to protect yourself from mosquito-borne illnesses could keep you from getting sick or even save your life.





Mosquito-borne illnesses in Miss. (Source: Miss. DOH):

West Nile virus: WNV has been reported in Mississippi in horses, birds, mosquitoes and humans. In humans, WNV infection can lead to dangerous conditions such as meningitis or encephalitis. Anyone can get WNV, but people over 50 years of age are more severely affected. Approximately 3 percent to 15 percent of people with WNV die. Unlike other mosquito-borne illnesses, certain species of birds (especially crows and blue jays) can also get sick and die from the disease, as can horses.

St. Louis encephalitis: SLE causes illness only in humans. Historically, it has been the most common disease carried by mosquitoes in Mississippi. SLE primarily affects the elderly, occurring in summer and early fall. SLE rarely causes death, although approximately 15 percent of the patients with severe symptoms die.

LaCrosse encephalitis: LAC can cause illness in humans, though it is more common in the midwestern U.S. rather than Mississippi. Cases occur from spring to fall, usually affecting children under 16 years of age. Only about one percent of people who become ill with LAC die.

Eastern Equine encephalitis: EEE causes illness in humans, horses and some birds. Very few human cases of EEE have ever occurred in Mississippi. Most infections occur in horses, from spring to fall. People of all ages can get the disease, but children are more likely to have severe illness or die. Approximately 30 to 60 percent of those who become ill with EEE die.