Take Steps to Prevent Mosquito-borne Illness

How much do you know about mosquito-borne illnesses?
   The main rule when it comes to breeding grounds for mosquitoes is that they need stagnant water in order to lay their eggs. What most people don’t realize is the surprising number of areas around their own house where mosquitoes can find the stagnant water they need. Any temporary body of water, from birdbaths to toy buckets, that is present for more than a week can be a mosquito-breeding habitat. Even flooded tire tracks and footprints in a muddy field have been known to produce dozens of mosquitoes each.

According to the Mass. Department of Public Health, more than 150 different kinds of mosquitoes have been found in North America, and 51 different kinds in Massachusetts. Only female mosquitoes bite to suck blood and use the blood to make eggs. Mosquitoes are attracted to carbon dioxide, a gas that humans and other animals breathe out, and can follow a stream of carbon dioxide from as far as 50 feet away.

Some mosquitoes carry germs that can make people and some animals sick. In Massachusetts, the diseases linked to mosquitoes are West Nile virus (WNV) and eastern equine encephalitis (EEE) virus.

EEE is relatively rare in humans, although there are occasional outbreaks in certain regions of the country. Fewer than 100 people have died from EEE in Massachusetts in the past 75 years, according to the Department of Public Health. In the U.S., approximately five to 10 EEE cases are reported annually. The risk of getting EEE is highest from late July through September, when more mosquitoes are present and active.

It is possible that some people who become infected with mosquito-borne viruses may not develop any symptoms or, in some cases, develop only flu-like symptoms. The incubation period for the virus from the time of an infected mosquito bite to onset of illness ranges from four to 10 days, and the illness can last one to two weeks. Those infected usually develop lifelong immunity.

There is no specific treatment for EEE. Antibiotics are not effective against viruses, and no effective anti-viral drugs have been discovered for the treatment of EEE. Severe illnesses are treated by supportive therapy, which may include hospitalization, respiratory support, IV fluids, and prevention of other infections.

West Nile virus is a mosquito-carried virus most commonly spread to people through the bite of an infected mosquito. About 80{06cf2b9696b159f874511d23dbc893eb1ac83014175ed30550cfff22781411e5} of people who are infected with WNV will have no symptoms. A smaller number of people who become infected, less than 20{06cf2b9696b159f874511d23dbc893eb1ac83014175ed30550cfff22781411e5}, will have symptoms such as fever, headache, body aches, nausea, vomiting, and sometimes swollen lymph glands. Fewer than 1{06cf2b9696b159f874511d23dbc893eb1ac83014175ed30550cfff22781411e5} of the people infected with WNV will develop severe illness, including encephalitis or meningitis.

There is no specific treatment for WNV infections. People with mild WNV infections usually recover on their own. People with severe WNV infections almost always require hospitalization.

I encourage community members to follow the following tips from the Department of Public Health to help protect themselves and their loved ones from illnesses caused by mosquitoes:

• Be aware of peak mosquito hours. The hours from dusk to dawn are peak biting times for many mosquitoes. Consider rescheduling outdoor activities that occur during evening or early morning.

• Apply insect repellent when outdoors. Use a repellent with DEET, permethrin, picaridin, oil of lemon eucalyptus, or IR3535, according to the instructions on the product label. DEET products should not be used on infants under 2 months of age and should be used in concentrations of 30{06cf2b9696b159f874511d23dbc893eb1ac83014175ed30550cfff22781411e5} or less on older children. Oil of lemon eucalyptus should not be used on children under 3 years of age.

• Clothing can help reduce mosquito bites. Wearing long sleeves, long pants, and socks when outdoors will help keep mosquitoes away from your skin.

• Mosquito-proof your home by draining standing water. Mosquitoes can begin to multiply in any puddle or standing water that lasts for more than four days, and mosquito breeding sites can be anywhere. Limit the number of places around your home for mosquitoes to breed by either draining or discarding items that hold water.

• Install or repair screens. Keep mosquitoes outside by having tight-fitting       screens on all of your windows and doors. –

Dr. Richard Gerstein is chair of Emergency Medicine at Baystate Mary Lane Hospital.