Mediterranean spotted fever in Salamanca, Spain. Epidemiological study in patients and serosurvey in animals and healthy human population.

Mediterranean spotted fever is a spotted fever group rickettsiosis caused by Rickettsia conorii. The fever has a recognized incidence in large geographic areas, and its presence in Salamanca Province (Spain) has been well documented since 1981. This work presents the results of the centralized prospective survey carried out in this area and was designed to study the epidemiological behavior of the disease and the prevalence of antibodies against R. conorii among animals and healthy human population. In 110 patients with confirmed diagnosis by an immunofluorescent antibody test we have observed a bimodal temporal curve of incidence of Mediterranean spotted fever in our zone and their predominant origin in villages under 2000 inhabitants. The serosurvey in a statistically representative sample of the human population of Salamanca shows a rate of 73.5% of reactive sera and percentages as high as 82% in samples from small villages. The seroepidemiological study of 300 animals reveals a widespread response to rickettsial antigens throughout the province. Immunofluorescent antibody titers of greater than or equal to 1:40 are present in 93% of dogs and high rates and titers are detected in other domestic mammals, suggesting their feasible epidemiological role in Mediterranean spotted fever.