Lyme disease is a tick-born illness found in many
regions of the United States, including parts of
Massachusetts. The tick that transmits Lyme disease
is the deer tick, and is much smaller than the common
wood tick. In order to transmit Lyme disease to
humans the larval deer tick must first feed on infected
animals, such as the white-footed deer mouse. The
larval tick matures into a nymph, the stage that
most commonly bites humans and transmits Lyme disease.
The nymph is about the size of a poppy seed and
can easily be missed. The adult tick can also transmit
Lyme disease. It is approximately the size of a
freckle.
In order to catch Lyme disease, a tick must be
infected. It is estimated that only 2% of larva
are infected. Adult infectivity varies significantly
averaging 30-50%. Also, the tick must be attached
for a minimum of 36 hours in order to transmit disease.
The risk of acquiring Lyme disease is quite low,
only 1-2%.
The clinical manifestations of Lyme disease are
diverse and nonspecific. Early Lyme disease is characterized
by a rash-usually a single red patch or target-like
lesion which grows over time and occurs in about
two-thirds of patients. Other symptoms may include
fever, muscle aches, joint pain, fatigue, headache,
and enlarged lymph nodes. If the disease progresses
unnoticed (usually in a child who had no initial
rash), arthritis may develop with tender swollen
joints. Very rarely children may develop neurologic
or cardiac manifestations.
The diagnosis of Lyme disease is difficult without
the characteristic rash. Laboratory tests are rarely
helpful. Diagnosis depends on knowledge of potential
tick exposures, and the clinical symptoms. Fortunately,
Lyme disease is easily treated with a variety of
oral antibiotics.
Recently a vaccine was developed. It is not approved
for children under 15 years of age. Three doses
are required. It is uncertain how long immunity
will last. The best treatment of Lyme disease, however,
is prevention. Protective clothing (lightweight
pants and long-sleeve shirts) should be worn in
tick-infested areas. Insect repellants may be temporarily
effective but should be used cautiously long-term
