Seroepidemiological survey of Mediterranean spotted fever in an endemic area ('Vallés Occidental', Barcelona, Spain).

A seroepidemiological survey of Mediterranean spotted fever was carried out in the region of 'Vallés Occidental', Barcelona (Spain). The prevalence of antibodies to Rickettsia conorii in human beings and dogs was determined by indirect immunofluorescence. In 200 samples of sera from subjects without former history of boutonneuse fever, an overall prevalence of antibodies to R. conorii of 11.6% was found. Seropositivity was significantly higher in the age group greater than 50 years. A significant correlation between seropositivity and habitat, social status, contact with dogs or risky practices was not found. In 48 sera from subjects with a history of Mediterranean spotted fever in the previous 10 years, the overall prevalence of antibodies was 68.7%, being 56.2% among those individuals who had suffered from the disease between 5 and 10 years earlier. In 103 dog serum samples collected during the summer, seropositivity was 36.8%. Positive sera were only detected in 1 of the 97 samples collected in winter, which suggests a relatively short duration of the canine immune response after contact with R. conorii.