Basic Information about Lyme Disease
- Lyme disease
is transmitted by the bite of a tick, and the disease is prevalent
across the United States and throughout the world. Ticks know
no borders and respect no boundaries. A patient's county of residence
does not accurately reflect his or her Lyme disease risk because
people travel, pets travel, and ticks travel. This creates a dynamic
situation with many opportunities for exposure to Lyme disease
for each individual.
- Lyme disease
is a clinical diagnosis. The disease is caused by a spiral-shaped
bacteria (spirochete) called Borrelia burgdorferi. The
Lyme spirochete can cause infection of multiple organs and produce
a wide range of symptoms. Case reports in the medical literature
document the protean manifestations of Lyme disease, and familiarity
with its varied presentations is key to recognizing disseminated
than 50% of patients with Lyme disease recall a tick bite.
In some studies this number is as low as 15% in culture-proven
infection with the Lyme spirochete.
than 50% of patients with Lyme disease recall any rash. Although
the erythema migrans (EM) or bulls-eye rash
is considered classic, it is not the most common dermatologic
manifestation of early-localized Lyme infection. Atypical forms
of this rash are seen far more commonly. It is important to know
that the EM rash is pathognomonic of Lyme disease and requires
no further verification prior to starting an appropriate course
of antibiotic therapy.
- The Centers
for Disease Control and Prevention (CDC) surveillance criteria
for Lyme disease were devised to track a narrow band of cases
for epidemiologic purposes. As stated on the CDC website, the
surveillance criteria were never intended to be used as
diagnostic criteria, nor were they meant to define the entire
scope of Lyme disease.
- The ELISA
screening test is unreliable. The test misses 35% of culture
proven Lyme disease (only 65% sensitivity) and is unacceptable
as the first step of a two-step screening protocol. By definition,
a screening test should have at least 95% sensitivity.
- Of patients
with acute culture-proven Lyme disease, 2030% remain
seronegative on serial Western Blot sampling. Antibody
titers also appear to decline over time; thus while the Western
Blot may remain positive for months, it may not always be sensitive
enough to detect chronic infection with the Lyme spirochete. For
epidemiological purposes the CDC eliminated from the
Western Blot analysis the reading of bands 31 and 34. These
bands are so specific to Borrelia burgdorferi that they
were chosen for vaccine development. Since a vaccine for Lyme
disease is currently unavailable, however, a positive 31 or 34
band is highly indicative of Borrelia burgdorferi exposure.
Yet these bands are not reported in commercial Lyme tests.