ONE HEALTH NEWSLETTER
Summer 2008
Lyme Disease in Florida: What You Need to Know
Kerry Clark, MPH, PhD
What is Lyme Disease?
Lyme disease (LD) is the most frequently reported arthropod-borne
disease in the United States (1). It occurs worldwide and is caused by several
species of spirochete bacteria within the Borrelia burgdorferi sensu lato
genogroup (2). B. burgdorferi sensu lato includes at least 12 species, four of
which are present in North America:B. andersonii, B. bissettii, B. californiensis,
and B. burgdorferi sensu stricto (3, 4, 5, 6). Thus far, only B. burgdorferi sensu
stricto has been proven responsible for human disease in the U.S. In the northeastern U.S., B. burgdorferi sensu stricto spirochetes are transmitted to
humans by the blacklegged tick, Ixodes scapularis (7), and maintained in nature
primarily by small rodents (8,9).
LD signs and symptoms include fever, headache, fatigue, and a skin rash
called erythema migrans (EM) that sometimes presents like a bullseye (Figure
1.). If left untreated in early stages, infection can spread to joints, the heart, and
the nervous system (neuroborreliosis). Lyme disease is diagnosed based on
symptoms, physical findings (e.g., rash, facial palsy, arthritis), and the possibility of exposure to infected ticks. Commonly used laboratory tests for LD may give equivocal, false negative, or false positive results. Although laboratory testing may be helpful for confirmation of infection, and for diagnosis during the later stages of disease, it is not presently necessary and generally not recommended for diagnosis of patients with EM (10). Most cases of LD can probably be treated successfully with several weeks of antibiotics if diagnosed promptly and therapy is initiated in the early stages of infection. The success rate for treatment of late stage illness is less certain. Therefore early recognition and treatment may be critical. Links to additional information on the presentation, diagnosis, treatment, and prevention of LD can be found at the Centers for Disease Control and Prevention (CDC) Division of Vector-Borne Infectious Diseases Lyme Disease webpage (10).
Does B. burgdorferi occur in Florida?
B. burgdorferi group strains, including B. burgdorferi sensu stricto, have been
isolated from birds, rodents, and ticks in southern states including Florida (9, 11). In the southeastern U.S., immature stages of I. scapularis feed on many different
species of vertebrates, but primarily on lizards (12, 13). B. burgdorferi group
spirochetes (several species) have also been detected by molecular methods in ticks from numerous sites in northern and central Florida (14), and in wild lizards in Florida and South Carolina (15). Therefore, it is documented that
B. burgdorferi group strains are established in Florida and other southern states. However, despite hundreds of reported cases of human Lyme disease from southern states each year, B. burgdorferi group spirochetes have still not been isolated from a human case in this region. Possible reasons for this are the lack of studies aimed at isolating the organism from human patients in the Southeast, geographic differences in the genetics of the spirochetes making it more difficult to cultivate some strains using standard methods, or as-yet-unknown reasons.
Complicating the matter.
Since the first report describing molecular detection of the hard tick relapsing
feverBorrelia species B. lonestari in lone star ticks (Amblyomma americanum) (16), numerous additional studies have reported its presence in lone star ticks throughout the eastern U.S. (17,18, 19, 20, 21). Since its initial discovery, B. lonestari has been investigated as the possible cause of Lyme-like illness, often referred to as southern tick associated rash illness (STARI), in humans in the southern U.S. (18, 20, 21, 22, 23). However, despite the efforts to date, very little evidence supports the notion that B. lonestari is the primary cause of STARI. To date only one published case report documented evidence of B. lonestari in association with Lyme-like illness and an EM-like skin lesion in a patient with an attached lone star tick (22). Alternatively, B. burgdorferi sensu lato DNA has been detected in host seeking adult lone star ticks in Florida (14), but evidence conclusively linking lone star ticks to human LD cases is also currently lacking.
So, does LD occur in Florida? Yes.
Since the standard case definition began in 1991, over 700 cases of LD in Florida have been reported to the CDC (10), and many of them were laboratory confirmed. Some of those infections may have been acquired in other states, but many of them were from patients who do not have a history of travel outside Florida. Nevertheless, awareness of the presence of risk for LD in Florida may still be poor overall. And, although the incidence of LD in Florida is much lower
than in hyperendemic areas of the northeastern U.S., the public and clinicians in
Florida need to be aware that LD should be considered in the differential diagnosis of patients with signs, symptoms, clinical history, and environmental exposure compatible with tick-borne illness. The possibility of other tick-borne infections or co-infections such as Anaplasmosis, Babesiosis, Ehrlichiosis, and Rickettsiosis should be considered, since their respective pathogens have also been identified in humans, wild vertebrates, or ticks in Florida (24, 25, K. Clark unpublished data). Also, keep in mind that although different tick species have specific seasonal activity patterns, at least some tick species is active anytime of the year in Florida. Some recommended steps to prevent Lyme disease and other tick- borne infections include improving awareness, avoiding tick-infested habitat, using insect/tick repellent, and checking for and removing attached ticks promptly.
What else should we know about LD in Florida?
The author of this article is presently conducting studies to determine the
cause of Lyme-like illness in human patients with suspected LD based upon EM-like skin lesions and/or symptoms consistent with early or late stage Lyme borreliosis in the southeastern U.S. The aims of the research include genetically characterizing pathogenic strains of the causative microorganisms and determining the tick or other arthropod vector species involved. Using
polymerase chain reaction assays (PCR) followed by DNA sequencing, the study
has thus far confirmed Lyme group Borrelia spp. DNA in blood samples from
several patients in Florida and other states throughout the country, but no evidence of B. lonestari infection. Furthermore, the evidence shows that both B.
burgdorferi sensu stricto, and a previously undetected group of B. burgdorferi
sensu lato strains, are associated with Lyme disease-like signs and symptoms in
patients from the southern U.S., as well as states outside this region.
Additionally, the findings thus far suggest that some cases of Lyme-like illness in
Florida and other states that do not meet the criteria for positive tests on the
Traditional B. burgdorferi ELISA and Western Blot antibody tests may be
attributable to this previously unnamed group of B. burgdorferi sensu lato. Those interested in learning more about or collaborating in this study can contact the author by email at kclark@unf.edu.