Lyme Disease
Lyme disease (LD) is caused by a bacterium known as Borrelia burgdorferi.
It is transmitted to people through the bite of an infected tick. In the
southeastern U.S. the black-legged tick (Ixodes scapularis) is the
suspected vector. The disease was first identified along the Connecticut River
in 1975, and is the most commonly reported vector-borne disease in the United
States. However, most cases are reported in the northeastern,
Mid-Atlantic, and north central regions of the country.
Map from CDC
Transmission Cycle
Normally, the life cycle of the black-legged tick begins with eggs in the
spring. The eggs hatch into larvae and then feed once before they molt into
nymphs and go dormant until the following spring. Then they feed again and molt
into adults. The larvae and nymphs feed on rodents, and it is usually at this
stage when the tick becomes infected. The adults feed on larger mammals,
including humans. Studies have shown that both nymph and adult ticks need to be
attached for more than 24 hours to effectively transmit the infection. For this
reason, it is important to regularly check for ticks and remove them
immediately.
Ixodes scapularis
Symptoms and Treatment
Between 60 and 80% of people will develop a red, "bull's eye"
rash (erythema migrans or EM) three to 30 days after being bitten by an infected
tick. This rash does not always appear at the site of the
bite, and may occur on another part of the body. Other symptoms include fever,
headache, chills, fatigue, stiff neck or muscle aches. Later stage symptoms may
not appear until months or years after the bite and can include problems with
the brain, heart, joints and muscles. Patients treated with antibiotics early
after the infection usually recover quickly and completely. A few patients,
especially those diagnosed in the later stages of disease, may have persistent
or recurrent symptoms. These patients may benefit from a second course of
antibiotic therapy. However, longer courses of antibiotic treatment have not
been shown to be beneficial and have been linked to serious complications.
Erythema migrans (EM)
Lyme Disease in Florida
In Florida, 554 cases of Lyme disease were reported from 1999 through 2008
(average 55 cases per year). Of these, 30% were acquired in Florida
and 70% were acquired while the person was traveling in another state or
country. Over half (56%) the cases were female, and the average age was 42 years
(range 0 - 87 years). The majority of cases were white (87%) and non-Hispanic
(82%). Of the infections acquired in Florida, the majority were reported from counties in
the northern and central regions of the state. The number of cases increased
during the summer months and peaked in July, though cases are typically reported
in Florida year-round.
Prevention of Tick-borne Diseases
Other Resources
Centers for Disease
Control and Prevention (CDC) Lyme Disease
CDC Interactive US Lyme Disease Map
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