Fever after a tick bite:: Clinical manifestations and diagnosis of acute tick-borne infections in North-Eastern Switzerland

Background: Different tick-borne infections can cause an acute febrile illness. The study objectives were to investigate the clinical manifestations and diagnosis of infections among patients who presented with fever after a tick-bite, and to detect newly described pathogens, including Ehrlichia, Babesia and Rickettsia helvetica, in North-Eastern Switzerland. Patients and methods: We studied 75 patients (41 male, 34 female, median age 38 years, among them 10 children) who had fever within 3 weeks after a tick-bite. Paired sera were tested for antibodies to Borrelia burgdorferi, tick-borne encephalitis virus, Anaplasma (Ehrlichia) phagocytophila, Babesia microti, B. divergens, and Rickettsia helvetica. In addition, microscopy and polymerase chain reaction was used to detect Ehrlichia. Clinical data were obtained at baseline and at 1 and 2 year follow-up. Results: Tick-borne infections were confirmed or possible in 36 (48%) patients: 7 (9%) Erythema migrans, 6 (8%) other specific manifestations of Lyme borreliosis, 6 (8%) Lyme borreliosis presenting as non-specific febrile illness, 8 (11%) tick-borne encephalitis, 7 (10%) granulocytic ehrlichiosis, 1 B. microti infection in a traveler from the US and 6 (8%) dual infections. in 8 (11 %) patients serological findings were suggesting possible acute or past R. helvetica infection. Conclusion: Among patients with fever after a tick-bite, Lyme borreliosis was most frequently found. There was no evidence for babesiosis among the resident population. Serologic data suggest that human granulocytic ehrlichiosis and R. helvetica infections may be endemic in Switzerland. Among 50% of the patients no tick-borne infections could be diagnosed.