The Trouble With Ticks: A Common Source of Illness
Medscape
Laurie E Scudder, MS, PNP
Tick-Borne Illness
The continued emphasis on infectious disease at the ACNP meeting continued with a presentation on management of tick-borne illnesses by Melissa Roberts JD, MSN, FNP, a clinical instructor in the Graduate School of Nursing at the University of Missouri, Kansas City.
Tick-borne diseases are the most common vector-borne illnesses in the United States. The mechanism of transmission of disease through tick bites is not well understood, though it is speculated that pathogens harbored in the gut of ticks may migrate to their salivary glands during a blood meal and are then transmitted to the host via the bite.
Ticks are ubiquitous in the United States, with multiple tick types, all members of the class Arachnida, responsible for 7 distinct clinical diseases. In the northeastern and middle Atlantic states, the deer tick carries the spirochete that causes Lyme disease. The Rocky Mountain wood tick and the American dog tick, found in both the eastern and western United States, spread Rocky Mountain spotted fever. Ticks are also responsible for 5 other less common, though quite distinct, diseases, including ehrlichiosis, tularemia, Colorado tick fever, tick paralysis, and relapsing fever.
As is the case with mosquito-borne illnesses, the mainstay of therapy for tick-borne illnesses is not treatment, but prevention, with a focus on reducing exposure to ticks through avoidance of tick habitats, use of tick repellents and protective clothing, and frequent tick checks, especially following a period of time outdoors in a wooded area.
Lyme Disease
Lyme disease is the most common of the tick-borne diseases in the United States, with almost 24,000 cases reported in 47 states in 2002, an increase of 40% over the incidence in 2001. Twelve states, Connecticut, Delaware, Maine, Maryland, Massachusetts, Minnesota, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, and Wisconsin, accounted for 95% of cases reported nationally.
Lyme disease, caused by Borrelia burgdorferi, is usually diagnosed and treated according to clinical manifestations, most notably a classic erythema migrans rash that occurs in up to 50% of infected patients. Laboratory testing is useful for patients with confusing presentations, although no single serologic test is definitive.
Lyme disease is stratified into 3 stages: early localized, early disseminated, and late disease. Treatment with doxycycline in patients older than 8 years or amoxicillin in those younger than 8 at the early localized stage is universally effective. Generally, the longer the patient has been ill prior to therapy, the longer the duration of treatment must be, and the need for more aggressive treatment increases. The duration of therapy should be guided by clinical response, rather than by an arbitrary (eg, 30-day) treatment course.
