Rickettsial tick bite fever: clinical aspects and laboratory diagnosis 1

Abstract

Since the last decades of the past century the frequency of rickettsial tick-bite fever has extremely increased. Patients often do not feel or realize a tick-bite. The most important diagnostic criterion after a tick-bite is a blue-red, later black skin ulcer with a black rim, called eschar or tache noir, and local lymph adenopathy. Clinical diagnosis can already be based on these symptoms. In some cases, the typical dark skin discoloration is absent or the color change may be misinterpreted as a minor skin injury. Also, exanthems occur and are of a maculo-papulous appearance. They show different variations and are often absent. In serological diagnosis, nearly half of the patients show antibodies against rickettsiae. Doxycycline as the drug of choice for therapy with one-day treatment (2×200 mg) has proven very effective. Alternative antibiotics include josamycin and ciprofloxacin. Whenever fever, head and/or muscle pain occur combined with typical skin involvement, particularly an exanthem or an eschar, tick-bite fever should be taken into consideration as a differential diagnosis when travelers have returned from a region where rickettsiae are known to be transferred by tick-bites. In returning travelers from defined areas of the American continent, Rocky Mountain spotted fever should be considered because of its complicated course with a mortality rate up to 5%. That is why in all cases, immediate antibiotic therapy should be initiated. Only then a quick defervescence can be accomplished after a one-day antibiotics therapy. © 2009 by Walter de Gruyter Berlin New York.