Seroprevalence of Coxiella burnetii infection (Q fever) in sheep farms located in Sicily (Southern Italy) and related risk factors

Q fever is an important and widespread zoonotic disease caused by the bacterium Coxiella burnetii, which has been recently reclassified as belonging to the order Legionellales. Q fever in humans is considered an endemic, mostly occupational, disease in several Mediterranean Countries. The infection is often asymptomatic in ruminants but infected animals excrete the bacteria into the environment, mainly during and after parturition or abortion. The aim of this study was to estimate the seroprevalence of C. burnetii infection and related risk factors in Sicilian ovine farms. A total of 6641 serum samples, from sheep belonging to 205 flocks, were examined by Enzyme Linked ImmunoSorbent Assay (ELISA). The seroprevalence at the animal level was 18% (95% CI), while at farm level it was 73.6% (95% CI). Moreover, an evaluation of potential risk factors was carried out on farms, including: farm size, contact with other animals, production type, farm localization and presence of water sources. The multivariate analysis indicated only two factors significantly associated with C. burnetii seropositivity: flock size (chi(2) = 10.82; p < 0.0010) and altitude of the farm (chi(2) = 4.28; p < 0.0386). These findings represent a first piece of information on Coxiella burnetii circulation in the examined areas. There is actually no specific vaccination plan to reduce the infection prevalence in animals; therefore, a better knowledge on the pathogen spreading could be helpful to take adequate preventive measures, especially considering the potential consequences and risks for human public health too.