Ticks are blood-sucking parasites of people and animals. Ticks cause illness by acting as vectors for pathogens, or by secreting toxins or venoms. Ticks carry more types of infectious pathogens than any other arthropods except mosquitoes. The most important of these include Borrelia (responsible for Lyme disease and relapsing fever), Rickettsia (eg, Rocky Mountain spotted fever [RMSF]), Ehrlichia (ehrlichiosis), viral pathogens (eg, Colorado tick fever), and babesiosis. Rashes are prominent in Lyme disease, RMSF, and southern tick associated rash illness (STARI), sometimes present in relapsing fever, uncommon in Colorado tick fever, and absent in babesiosis.
Clinically important ticks in North America include Ixodes dammini, the deer tick (Lyme disease and babesiosis), Dermacentor andersoni, the wood tick (RMSF and Colorado tick fever), Dermacentor variabilis, the dog tick (RMSF, ehrlichiosis), and Amblyomma americanum, the lone star tick (a very widespread tick implicated in the transmission of Lyme disease outside of the range of I dammini as well as STARI and ehrlichiosis). More than 40 species of ticks can cause tick paralysis. In North America, the most common cause is D andersoni, but A americanum and Ixodes species have also been associated with tick paralysis.
Tick paralysis develops 5 to 6 days after an adult female tick attaches. Over the next 24 to 48 hours, an ascending, symmetric, flaccid paralysis develops. Alternative presentations include ataxia and associated cerebellar findings without muscle weakness or isolated facial paralysis. Resolution of the paralysis after removal of the tick establishes the diagnosis.
Management and Disposition
If still embedded, the tick should be removed promptly by grasping it as close to the skin surface as possible, using blunt curved forceps or tweezers. The tick should be pulled out with slow, gentle traction, taking care not to crush or squeeze the body, which may result in injection of contaminated tick fluids. Other methods of tick removal—such as application of fingernail polish, isopropyl alcohol, or a hot match head—have not been proven to effect detachment and may induce regurgitation of tick contents into the wound.
Patients with tick paralysis may require supportive care, including mechanical ventilation. Patients with tick-borne illnesses may require admission for supportive care or intensive antibiotic treatment, but when clinically appropriate may be treated as an outpatient with appropriate antibiotic therapy.
Prevention of tick bites includes the use of protective clothing containing N, N-diethylmetatoluamide (DEET).
A clear history of a tick bite is present in less than one-third of Lyme disease cases.
Unusual neurologic presentations, particularly bilateral peripheral seventh-nerve palsies, should prompt consideration of Lyme disease.
Patients with paralysis in endemic areas should be thoroughly searched for embedded ticks.
Deer Tick. Ixodes dammini, the deer tick, is a vector of Lyme disease and babesiosis. (Photo contributor: Centers for Disease Control and Prevention, Atlanta, GA.)
Wood Tick. Dermacentor andersoni, the wood tick, is a vector of Rocky Mountain spotted fever and Colorado tick fever. (Photo contributor: Centers for Disease Control and Prevention, Atlanta, GA.)
Lone Star Tick. Amblyomma americanum, the lone star tick, has been implicated as a vector in STARI. (Photo contributor: Sherman Minton, MD.)
Imbedded Tick. This lone star tick was found imbedded into the patient’s shoulder. It was easily removed intact with tweezers. (Photo contributor: R. Jason Thurman, MD.)
American Dog Tick. Dermacentor variabilis, the dog tick, is a vector of Rocky Mountain spotted fever and ehrlichiosis. (Photo contributor: R. Jason Thurman, MD.)
Erythema Migrans Rash. This erythema migrans rash was located at the site of a tick bite in a patient who developed southern tick associated rash illness (STARI). Erythema migrans rash is also associated with Lyme disease. (Photo contributor: Shannon B. Snyder, MD.)