Insect Bites, Lyme Disease,
and Eastern Equine Encephalitis

by Cecilia Mullen, R.N.C., N.P.

August 11, 1999

Insect bites are a nuisance but in rare instances, insects can transmit certain diseases. Some mosquitoes in southeastern Massachusetts can transmit eastern equine encephalitis and some deer ticks can transmit Lyme disease or ehrilichiosis and some dog ticks can transmit Rocky Mountain spotted fever.

Fortunately, only a very small number of insects are infected, so being bitten by a mosquito or tick does not mean a person will develop the illness.

Lyme Disease

Lyme disease is an infection caused by a bacteria spread by the tiny deer tick. The disease is most likely to be spread between May and early autumn when ticks are most active and people spend their greatest time outdoors.

Deer ticks are most often found in coastal areas when the ticks cling to plants and grasses. The ticks cannot jump or fly, they climb onto animals or people who brush against the plants. People who are repeatedly exposed to these areas run the highest risk of developing Lyme disease. These include outdoor workers, people who hike, walk or exercise in the outdoors and people who live and go outdoors in endemic coastal areas, such as the Cape or Islands. Deer tick larvae and nymphs are so small they can be difficult to see. They are the size of the period at the end of this sentence.

Early symptoms of Lyme disease include an unusual rash where the tick was attached, which develops anywhere from 3-32 days after a bite. It starts as a small red rash that spreads and then clears in the center, like a donut. Other symptoms include burning or itching, hives, swollen puffy eyelids and flu-like symptoms such as fever, headache, stiff neck, sore muscles and joints, fatigue, sore throat and swollen glands. The symptoms may go away in a few weeks but the infection remains. About half of the infected people will develop the rash again in other places. Treatment with antibiotics clears up the rash within days although treatment must continue for one month to prevent later problems.

Late stages of Lyme disease affect the joints, nervous system and the heart. About 60% of untreated infected people develop arthritis and about 10% of untreated infected people develop weakness and nerve palsies. Even less than 10% develop heart problems.

Eastern Equine Encephalitis

EEE is a rare but serious viral disease. Typical symptoms include high fever (103-106° F) stiff neck, headache, fatigue. Mental confusion signifies the most dangerous symptom. Fewer than 80 cases have been reported in Massachusetts since 1938. EEE is spread by mosquitoes and there is no cure. Testing of mosquitoes is done routinely to monitor the emergence of the virus. The only way to protect yourself is to keep mosquitoes from biting you.

Rocky Mountain Spotted Fever

This is a bacterial illness transmitted by a dog tick. Dog ticks are larger than deer ticks. The disease typically appears as a high fever accompanied by a severe headache and fatigue. A rash that spreads to the palms of the hands and soles of the feet occurs in about half of all cases. Antibiotic treatment is usually effective.

Ehrlichiosis

This disease has been primarily seen on the Cape and Islands, and is transmitted by the deer tick. Its typical onset is sudden fever, headache, aches, nausea and vomiting, sweats and chills. Symptoms can rapidly become life threatening and require immediate medical treatment. A new strain of ehrlichiosis has been found in the mid west as well, although not enough cases have been found to designate the area as high risk.

How can tick bites be prevented?

  1. Avoid walking in tall grass, woods or dunes where ticks live.
  2. Wear light-colored long-sleeved shirts and pants and tuck pant legs into socks.
  3. Use insect repellants that contain DEET. Read labels carefully and don't overapply.
    1. Avoid using repellants with more than 10-15% DEET on children and avoid applying on their hands and faces. Do not use on infants.
    2. Adults should avoid repellants with more than 30-35% DEET.
    3. Wash repellants off skin as soon as you return indoors.
  4. Check for tick bites daily. Favorite tick places include armpits, along hairline, behind ears, on the legs and groin.
  5. To remove a tick, use tweezers to grip mouth parts firmly and pull straight out. Then drown the tick in alcohol. Wash bitten area in alcohol.
  6. If you are considered a high risk individual:
    1. those who work outdoors in endemic areas such as the coast
    2. those who spend a lot of time outdoors in endemic areas:

Consider receiving the new Lyme vaccine. This involves three injections. The first injection is followed by a second injection one month later and provides approximately 30% protection against Lyme Disease. The third injection is given one year later and provides 50-80% immunity against Lyme disease. The vaccine is new and it is unknown how long protection will last. This vaccine should be used as a supplement to the above-mentioned prevention techniques and will not provide complete immunity.

How can mosquito bites be prevented?

  1. Wear long-sleeved shirts and long pants.
  2. Stay indoors at dusk and dawn.
  3. Make sure screens are repaired.
  4. Avoid stagnant water collection outside the home.
  5. Use repellants with DEET.
  6. Chemical aerial spraying is used only if there is a great risk of people getting EEE. Some swampy communities will spray non-chemical pesticides to control mosquito larvae.

For further information call the Massachusetts Department of Public Health:
617-983-6800.

Portions of this article were excerpted from the Massachusetts Department of Public Health Fact Sheets about insect bites and Lyme Disease and Eastern Equine Encephalitis.

Cecilia Mullen is a nurse practitioner at Granite Medical Group. The information in this column is not intended to diagnose individual conditions. Readers should see their own doctors about specific problems.

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