Getting to Know the Two Most Prevalent Mosquito-Borne Illnesses in Massachusetts, West Nile Virus and Eastern Equine Encephalitis

Author: Mosquito Squad of Chelmsford & Cambridge

As more confirmations come in on mosquitoes testing positive for West Nile Virus (WNV) in our area, we are reminded about the importance of reducing your risk for contracting a mosquito-borne illness. This past week, The South End Patch reported that Boston has raised the threat level to moderate for West Nile Virus after two positive tests from mosquito pools in Jamaica Plain and Hyde Park at the end of July, and because the number of trapped mosquitoes has doubled.  We are also reminded almost nightly of the disease being found in Andover, Wakefield, Middleton, and other areas around us on the evening news.

While the incidence of West Nile on the North Shore has yet to convey a human testing positive for the virus this season, the conditions are favorable for more West Nile cases and other mosquito-borne illness to emerge in the coming weeks. Although, there are many types of mosquito-borne illness across the US, the two most prevalent in Massachusetts are West Nile virus and Eastern Equine Encephalitis.  The impact of both these illnesses depends on weather, populations of mosquitoes, and the presence of infected birds. With this in mind, Mosquito Squad of the North Shore wants to educate residents about these two mosquito-borne illness and their symptoms.

Public enemy number one is West Nile Virus

West Nile Virus is an arbovirus that is spread through the bite of an infected mosquito. West Nile Virus can produce one of three outcomes in humans. These three distinct reactions to the illness are asymptomatic, fevers and neuroinvasive.  Neuroinvisive reactions can include West Nile Meningitis or West Nile Encephalitis. Each of which can cause inflammation of the brain and damage to the central nervous system.

Asymptomatic infections generally display few or no symptoms following a typical 2-8 day incubation period. If the disease worsens, those infected can then develop febrile West Nile. Symptoms of febrile West Nile usually include headache, chills, sweatiness, fever, and joint pain similar to the onset of being infected with the seasonal flu. In some cases the patient may experience vomiting, diarrhea and other gastrointestinal symptoms, but these are less common. In most cases these febrile symptoms will resolve within 10 days. More severe cases of West Nile can cause Meningitis and Encephalitis which can lead to coma and death. Last summer, 33 cases of West Nile virus were reported in Massachusetts—the highest in the state’s history—resulting in one known death.

Eastern Equine Encephalitis

Although the name may imply this illness is strictly confined to the equine set, Eastern Equine Encephalitis is also the source for human infection. Eastern Equine Encephalitis (EEE), is a viral disease which is transmitted to humans through the bite of a mosquito that has fed from birds infected with the virus. Horses and people are considered a “dead end host”, which means once infected,  the virus cannot be passed on. The disease is quite serious, and in some cases fatal. Last year, there were seven diagnosed human cases of EEE, and three of these cases claimed the lives of three Massachusetts residents. This disease also claimed the lives of numerous horses last season. The commonwealth historically has the second-highest incidence of EEE, after Florida. Surrounding states have rarely seen the disease, but last summer Vermont reported its first cases of the virus, according to an article published last month by boston.com.

EEE follows a “burn-out” pattern, meaning a viral strain gets introduced, spreads, and then eventually burns itself out. So last year’s strain could return this year, or it could have burned itself out last fall, only time will tell. Initial symptoms are flu-like such as fever, sore throat and headache, but the illness usually progresses to more serious symptoms affecting the central nervous system which can lead to seizures, coma and in some cases death. The disease has a 33% mortality rate, according to the Centers for Disease Control and Prevention.

Since there is no vaccine or cure for either virus, only treatment for symptoms, it is crucial to implement safe mosquito practices and instill the expertise of a licensed mosquito control professional. Prevention and control are the best weapons against coming into contact with a potentially infected mosquito.

Mosquito Squad of the North Shore offers an intensive mosquito control program that controls and prevents mosquitoes all season. Our safe and effective barrier sprays are applied on schedule throughout the mosquito season and ensure no gaps in your mosquito control. We also offer an automatic mosquito misting system that is highly effective in both commercial, barn and residential settings.

Our goal is to completely protect you from mosquitoes and the many diseases they carry for the entire season. Contact Mosquito Squad of Chelmsford & Cambridge to learn more at (978) 381-4028.