Prevalence of antibodies to spotted fever group rickettsiae in human beings and dogs from and endemic area of mediterranean spotted fever in Catalonia, Spain.

We assessed the prevalence of antibodies to spotted fever group rickettsiae in human beings and dogs by indirect immunofluorescence in the region of 'Vallés Occidental', Barcelona (Spain). In the group of 150 serum samples from patients without former history of Mediterranean spotted fever, 12 had antibodies to Rickettsia conori. The overall seroprevalence was 8% (95% confidence interval, 4.6% to 13.5%). There were no statistically significant differences between the mean ages of patients with positive and negative antibodies to R. conorii. However, seropositivity was significantly more common among patients living in semi-rural areas. In the group of 138 dog serum samples, 36 (26.1%) sera had antibodies to R. conorii. When the present results were compared with those obtained in a previous seroepidemiological survey carried out in the same geographical region in 1987, no significant differences were found. Therefore, although the epidemiological markers have dropped, this does not absolutely confirm the decrease of the presence of R. conorii in this area.