Analysis of seroprevalence against Coxiella burnetii in a sample of farm workers in Western Sicily.

Abstract

Little is known about the development of chronic Q fever caused by Coxiella burnetii in occupational risk groups and in the general population in Italy, as well as in many countries in the world. The aim of this study was to highlight the presence of the infection in a sample of workers operating outdoors (but not directly in contact with animals), in three provinces of western Sicily, in order to detect the human seroprevalence and compare the obtained data with those found in animals raised in the same territory. The study included 126 generic seasonal agricultural workers (labourers), 84 male and 42 female; none of whom were aware of any previous contact with Coxiella burnetii. Their immunologic status against Coxiella burnetii was tested through research and titration of both phases I and II specific antibodies (IgG) with an indirect immunofluorescence assay, using anti-antibodies labeled with fluorescein isothiocyanate. All data were statistically analyzed, comparing all positive results from the three provinces through variance analysis, and then comparing human results with those obtained from animals raised in the considered areas, specifically, 1,511 cows, 46 of which were found positive (3.04%), and 3,391 sheep, 548 of which were found positive (16.16%). Anti-Coxiella antibodies were found in nine of 42 females sampled (21.4%; 95%CI=[9.0-33.8]) and 21 of 84 males sampled (25.0%; 95%CI=[15.7-34.3]). 60% (18 of 30; 95%CI=[42.5-77.5]) of seropositive samples were positive either for Phase I antigen or for both Phase I and II antigens, representing cases of chronic infection. Applying Spearman's rank correlation, the percentage of seropositive humans was significantly correlated with that observed for sheep (r=1.00; p<0.001), but not for cows (r=-0.5; p=0.667). The results obtained, although based on a small sample, suggest that the disease is present in the territory of Western Sicily, both in animals and in humans. A closer collaboration between doctors and veterinarians is therefore necessary to fight against the spread of the infection.