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A series of sudden unexpected cardiac deaths among Swedish elite orienteerers in the 1980s have resulted from the combination of infectious diseases and physical exercise. Studies in the late 1990s have pointed to Chlamydia and Barontella, which both had a high seroprevalence among Swedish elite orienteerers. We conducted a case–control study aimed to elucidate the serologic prevalence of rickettsial diseases among Danish elite orienteerers. Ticks are known as vectors for some rickettsial diseases. None of the orienteerers had a positive antibody titer against any of the tested Rickettsia despite a very high frequency of tick bites in this group. [ABSTRACT FROM AUTHOR]

Sudden death in Swedish orienteers was demonstrated to be significantly associated with antibodies to Bartonella sp. To test if these antibodies could be related with tick exposure, we searched Bartonella sp. in Ixodes ricinus ticks using specific PCR amplification and culture. No Bartonella sp. was detected in 167 ticks tested.

Bartonella spp. have been identified as aetiological agents in culture-negative infective endocarditis (IE). Coxiella burnetii may cause chronic Q-fever with endocarditis, 334 blood samples collected from 329 patients (334 episodes) with IE diagnosed between 1984 and 1996 in Göteborg, Sweden, were investigated for antibodies to Bartonella spp. and C. burnetii. 71 of the episodes (21%) were blood culture negative. A microimmunofluorescence assay revealed immunoglobulin G (IgG) antibodies to Bartonella in 13 of the culture verified episodes and in 2 of the culture-negative episodes. Three of the patients had IgG antibodies to > or = 200 in the blood culture-verified group, but none had a titre > or = 800, the cut-off level for Bartonella endocarditis. One patient had elevated antibodies to C. burnetii, diagnosing chronic Q-fever endocarditis. In conclusion, serologically verified Bartonella endocarditis is not prevalent in western Sweden and Q-fever endocarditis is rare.