Serological evidence of exposure to Coxiella burnetii in sheep and goats in central Portugal.

The recent outbreak of Q fever in The Netherlands warned European health authorities of the need of studying Coxiella burnetii. In Portugal, little is known about C. burnetii infection in animals. A cross-sectional study was designed to investigate the exposure to C. burnetii in sheep and goats in the Central region of Portugal, estimating the herd and individual prevalence. A serosurvey was conducted in a two levels random sampling of 89 herds and 460 animals. Individual blood samples were collected from animals older than 6 months, and specific antibodies anti-C. burnetii were detected by ELISA testing. Results showed a global herd prevalence of 32.6% (95% CI: 23.1-42.1%). Herd prevalence was higher in mixed herds (38.5%; 95% CI: 12-65%) and in sheep herds (37.5%; 95% CI: 21-54%) than in goat herds (28.8%; 95% CI: 17-41%). Global individual prevalence was estimated at 9.6% (95% CI: 6.9-12.2%), and it was higher in goats (10.4%; 95% CI: 7.8-13%) than in sheep (8.6%; 95% CI: 5.8-11.4%). Sample positive percentages (S/P) ranged from 41.5% to 185.9%. S/P percent higher than 100 was found in 18.2% (8/44) of sera from distinct herds. Positive results were significantly associated with goats, older animals and larger herds. These results revealed the presence of C. burnetii in small ruminants evidencing their potential role in the infection cycle.