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.

Q fever is a widespread disease affecting reproduction in dairy cattle. Several risk factors can increase the possibility of the herd becoming infected and the persistence of infection. The aim of this study was to characterise the dynamics of C. burnetii infection in affected herds and to evaluate reproduction problems and risk factors using a questionnaire within infected and infection-free dairy herds. In total, 25 farms that were serologically positive or shedding C. burnetii DNA in milk and 14 C. burnetii infection-free farms in Latvia answered the questionnaire. Ten positive herds were studied by testing individual blood and milk samples from up to 10 animals at two times separated by 7.5 to 13 months. The number of serologically positive and suspicious animals was higher in the second sampling even though several animals were culled. In the positive herds, the percentage of dystocia, stillborn calves and abortions during the last year was significantly (p=0.001; 0.01; 0.005, respectively) higher than in the negative herds. Several significant factors were found for the presence of Q fever infection, such as the herd size, the regional population density of ruminants, artificial ventilation systems, and frequent farm visitors. Deratisation was less practised in the negative farms and the presence of ticks was observed more often in the negative farms. Only two identified risk factors can be mitigated – the ventilation system and frequent farm visitors. The other factors cannot be changed arbitrarily but they have to be taken into account by decision makers.

Q fever is an important zoonotic disease worldwide. The main sources of human infection are inhalation of aerosols containing Coxiella burnetii bacteria and exposition to infected materials during parturition or slaughtering. The high-risk group includes people who work directly with infected livestock, such as farmers, veterinarians, veterinary medicine students, slaughterhouse and laboratory staff. Here we present a pilot study of risk-group human seroprevalence to C. burnetii in Latvia. The study included 240 sera samples — 190 from the risk groups and 50 from the control group. Samples were tested with Coxiella burnetii (Q-fever) Phase 1 and 2 IgG ELISA kits. All sera from the control group were negative. The seroprevalence among risk group persons was 8.04–11.54%. No statistically significant differences were observed between genders. The highest percentage of seropositive and equivocal sera samples (25%) were detected in age categories 39–48 years and 49–58 years. Working as a practicing veterinarian or former veterinarian was the only risk factor identified as statistically significant, and belonging to the risk group in general. The geographical distribution of seropositive risk group participants indicated that they tend to located more in the northern, central, and eastern part of the country.