--You first need to identify the tick. Lyme disease (Borrolia burgdorferi) and Babesiosis are transmitted by the Ixodes ricinus complex (Ixodes scapularis [formerly I. Dammini] in the northeastern and midwestern U.S. and Ixodes pacificus on the West Coast). The common dog tick (Dermacentor variabilis) has been associated with Ehrlichiosis (Ehrlichia chaffeensis) and not Lyme or Babesiosis. Ehrlichiosis is generally confined to the south and south central U.S. If the tick is a dog tick, generally no treatment is indicated. If the tick is Ixodes, then duration of attachment is a factor.

--The Borrolia spirochete survives in the midgut of Ixodes tickes and does not generally penetrate the tick's salivary glands until 24 hours after the start of the blood meal. The risk of infection increases dramatically after 36 to 48 hours. If the tick is thought to be recently attached, and this can be established with reasonable certainty (e.g., the patient examined himself nightly and the newly discovered tick does not appear to be engorged), observation alone is recommended, as the side effect profile from antibiotics is thought to outweigh the risk of contracting Lyme. In this case, repeat tiers 4 to 6 weeks should be checked. The development of symptoms (an EM rash or Lyme meningitis) or a four-fold rise in titers would be an indication for treatment.

--If the tick is engorged, the duration of attachment is uncertain and/or the tick is from an endemic area (as is the case here), and antibiotic prophylaxis seems appropriate.

The following regimens have been suggested:

a) Doxycycline 100 mg PO BID for 10-30 days
b) Tetracycline 250 mg PO QID for 10-30 days
c) Amoxacillin 500 mg PO TID for 10-30 days

The duration of treatment should be toward the shorter end of the range for the EM rash alone, and toward the longer end of the range for symptoms of early disseminated infection (multiple erythema lesions, arthralgias, neck stiffness, parasthesias).

(Note the recommendation regarding the prophylaxis are controversial with regard to patient selection as the consequences of not treating Lyme disease are devastating. Many authors recommended prophylaxis of all tick bites.)