High seroprevalence of Coxiella burnetii infection in Eastern Cantabria (Spain)

Background Coxiella burnetii is the causative agent of Q fever, a worldwide zoonosis which shows a wide diversity of clinical manifestations. The objective of this seroepidemiological study was to estimate the prevalence of antibodies to C. burnetii in a representative population of the Eastern area of the Cantabrian Community (Northern Spain). Methods A cross-sectional study was conducted in 595 subjects from Eastern Cantabria. Four different zones (one urban and three rural zones) were defined according to the geographical characteristics of the area and the economic activities of the population. The population sample for this study was collected between December 1994 and March 1995, and was stratified by age, sex and municipality of residence. IgG and IgM antibodies against C. burnetii were assayed by an indirect immunofluorescence technique. Results The prevalence of anti-phase II Coxiella IgG (titre greater than or equal to 1:16) was 48.6% (95% confidence interval: 44.6-52.6%), with 81.3% having a titre of greater than or equal to 1:64. The prevalence of IgG increased with age, ranging from 12.0% in people <15 years to 70.3% in those >65 years (P < 0.001). The antibody detection rate was higher in males (53.6%) than in females (43.3%) (P < 0.01). The prevalence of anti-phase II Coxiella IgG was less among subjects living in the urban zone (32.8%) than in those living in the other three rural zones: the two situated on the coast (54.0% and 54.9% respectively) and the inner mountainous zone (82.3%) (P < 0.001). Conclusions The prevalence of C. burnetii infection observed in this study is one of the highest reported in Europe. The eastern area of Cantabria is a hyperendemic area for Q fever.