Seroprevalence of infection by Coxiella burnetii in Canary Islands (Spain)

Objectives: The aims of our study were:(i) to know the seroprevalence of Coxiella burnetii infection in the Canary Islands, (ii) to evaluate its epidemiologic features and (iii) to compare the rates of seroprevalence using two different cut-offs (1:20 and 1:80) for the diagnosis of past infection. Methods: We analysed a representative sample of the canarian population. 662 sera were tested. For the detection of IgG and IgM antibodies against C. burnetii phase II antigens an immuofluorescence assay was used. The serologic screening for IgG detection begun with a 1:20 dilution. A titer of IgG greater than or equal to 1:80 along with a negative IgM were used as criteria for previous infection. Results: At an IgG antibody titer against C. burnetii of 1:80 as diagnostic for past infection, the observed global seroprevalence was 21.5%. If the cutoff used was 1:20, the observed prevalence increased up to 35.8% (p = 0.001). Significantly different seroprevalence rates were obtained at these different cutoffs when results were analysed for groups of age and socioeconomic status, but not for either the island of origin or for farmers. Conclusion: Our results strongly suggest that Coxiella burnetii infection is endemic in all the Canary Islands. Although it is more frequent in males above 30 years old, it do affect people of all ages, and thus it should be borne in mind in the face of any acute febrile syndrome.