Prevalence, Risk Factors, and Relationship between Reproductive Performance and the Presence of Antibodies against Coxiellosis in Dairy Farm Milk Tanks in the Northwest of Spain

Abstract

Q fever is an infectious disease caused by Coxiella burnetii that can affect both humans and animals. Given its consequences and the lack of epidemiological data published about its distribution and risk factors, we aimed to evaluate the prevalence of Coxiella burnetii at dairy farms in the northwest of Spain, identify which risk factors favor its occurrence, and the consequences on reproductive performance at the farm level. Bulk tank milk samples were collected from 262 farms and analyzed to identify antibodies against this bacterium. Additionally, data about potential risk factors and reproductive performance were obtained. A total of 60.1% of the farms tested positive for coxiellosis, and the main risk factors were the herd size, the purchase of livestock, and the geographical area. Additionally, conception rate and first-service conception rates were lower in positive farms, which also tended to have higher incidence of reproductive disorders after calving.Q fever is a zoonotic disease that has been associated with reproductive problems in animals. As there is little epidemiological data regarding the distribution and risk factors of this disorder in cattle, the objective of this study was to evaluate the prevalence of Coxiella burnetii among dairy herds in the northwest of Spain, and to determine the on-farm risk factors associated with the disease and its effects on reproductive performance. Bulk tank milk (BTM) samples were collected from 262 commercial dairy herds from A Coruña, Lugo, and Pontevedra provinces. Data about location, mean age, and herd management features were obtained. A commercial indirect ELISA kit was used to determine the presence of antibodies against C. burnetii in BTM samples. The relationship between seropositivity to C. burnetii and the risk factors was checked using a Pearson’s χ2 test and a classification tree analysis. In addition, a one-way ANOVA test and the Mann–Whitney U test were used to check the impact of seropositivity to C. burnetii on reproductive performance. A total of 60.1% of the farms tested positive for coxiellosis, the herd size, the external purchase of livestock, and the geographical area were identified as the main risk factors. Conception rate and first-service conception rate were significantly lower (p < 0.05) in positive farms (37.1 and 32.9%) compared to negative farms (39.8 and 36.1%). Similarly, positive farms had significant higher incidence of endometritis (13.7% vs. 11.2%, p < 0.05). Consequently, a high seropositivity and slightly negative effects of coxiellosis on reproductive performance were observed, which intensifies the need for further research, including the identification an active infection in positive herds and the characterization of the genotype.