By Alan S. Peterson, MD
Lyme disease is caused by the bacterium Borrelia burgdorferi and is often transmitted through the bite of an infected blacklegged tick, also known as a deer tick. It is the most common tick-borne disease in the Northern Hemisphere.
Typical symptoms include fever, headache, fatigue, and a characteristic skin rash. If left untreated, infection can spread to joints, the heart, and the nervous system.
In the past decade, Lyme disease has grown by 78%. Pennsylvania has reported more cases of Lyme disease than any other state due to increases in climate warming and moisture, white deer, and the white-footed mouse. The year 2016 saw 8,988 confirmed cases in PA. This averages to an incidence of 70 people per 100,000 of the population.
Pennsylvanians in all counties now are at risk for Lyme disease and should take steps to protect themselves when outdoors, including using insect repellent with DEET (20-30%), wearing long sleeve shirts and long pants, and checking for and removing any ticks when returning to enclosed surroundings.
Ticks can attach to any part of the human body but are often found in hard-to-see areas such as the
groin, armpits, and scalp. In most cases, the tick must be attached for 36 to 48 hours or more before
the Lyme disease bacterium can be transmitted to you.
Most humans are infected through the bites of immature ticks called nymphs. Nymphs are tiny (less
than 2 mm) and difficult to see; they feed during the spring and summer months. Adult ticks can also
transmit Lyme disease bacteria, but they are much larger and are more likely to be discovered and
removed before they have had time to transmit the bacteria. Adult Ixode ticks are most active during
the cooler months of the year.
Relative sizes of blacklegged ticks at different life stages
In general, adult ticks are approximately the size of a sesame seed and nymphal ticks are
approximately the size of a poppy seed.
Are there other ways to get Lyme disease?
- There is no evidence that Lyme disease is transmitted from person to person. For example, a person cannot get infected from touching another person who has Lyme disease.
- Lyme disease acquired during pregnancy may lead to infection of the placenta and possible stillbirth; however, no negative effects on the fetus have been found when the mother receives appropriate antibiotic treatment. There are no reports of Lyme disease transmission from breast milk.
- Although no cases of Lyme disease have been linked to blood transfusion, scientists have found that the Lyme disease bacteria can live in blood that is stored for donation. Individuals being treated for Lyme disease with an antibiotic should not donate blood. Individuals who have completed antibiotic treatment for Lyme disease may be considered as potential blood donors. Information on the current criteria for blood donation is available on the Red Cross website
- Although dogs and cats can get Lyme disease, there is no evidence that they spread the disease
directly to their owners. However, pets can bring infected ticks into your home or yard. Consider
protecting your pet, and yourself, through the use of tick control products on your animals.
- You will not get Lyme disease from eating venison or squirrel meat, but in keeping with general food safety principles, always cook meat thoroughly. Note that hunting and dressing deer or squirrels may bring you into close contact with infected ticks.
- There is no credible evidence that Lyme disease can be transmitted through air, food, water, or from the bites of mosquitoes, flies, fleas, or lice.
- Ticks not known to transmit Lyme disease include Lone star ticks (Amblyomma americanum), the American dog tick (Dermacentor variabilis), the Rocky Mountain wood tick (Dermacentor andersoni), and the brown dog tick (Rhipicephalus sanguineus).