Shedding of Coxiella Burnetii in Milk of Dairy Cattle and Evidence of Q Fever in Domestic Ruminants with Emphasis on Abortion Cases in Latvia

Q-fever is widespread globally. The goal of this study was to estimate the prevalence of Q-fever infection in Latvia among dairy cattle in 2018–2020, in comparison with that in 2012–2015. The shedding of Coxiella burnetii DNA in milk was assessed. Screening of blood samples of abortion cases for the presence of antibodies against Q-fever and testing of aborted fetuses for C. burnetii DNA were also carried out. Additionally, serum samples from clinically healthy cattle, sheep and goat were included. Overall, 18.34% of milk samples were positive, representing 11.02% of all tested sheds. In total, 20.62% of serum samples from the cattle that suffered abortions were positive or suspicious, representing 12.63% of all sheds. Only 3.33% of serum samples from clinically healthy cattle and 3.42% from sheep and goat were positive. The highest proportion of serologically positive and suspicious samples was observed in cattle that suffered abortion with age from three to nine years, and in the first and third gestation period. One dominant genotype of C. burnetii (MST61) was detected. Ruminant import from abroad was identified as a significant risk factor, as well as the dairy cattle population density.