Herd-level seroprevalence, molecular prevalence, and trends of Coxiella burnetii (Q fever) in cattle worldwide: A systematic review and meta-analysis.

Background and aim: Cattle are the reservoir host of Coxiella burnetii, a causative agent of Q fever. Pooling herd-level prevalence data from individual studies would help determine the global prevalence of C. burnetii in cattle herds. This study aimed to estimate the global herd-level seroprevalence and molecular prevalence of C. burnetii in cattle, explore sources of heterogeneity, and determine trends and cumulative evidence of the pooled prevalence over time.

Materials and methods: Relevant studies were retrieved from PubMed, Scopus, and Web of Science and then screened for possible inclusion. A random-effects model was used for all meta-analyses. Subgroup meta-analysis and meta-regression were used to explore some sources of heterogeneity associated with the pooled prevalence and to determine the trends of C. burnetii in cattle herds over the study years (1961-2020). A cumulative meta-analysis was used to determine the cumulative evidence of the pooled prevalence over the publication years.

Results: Of the 1541 citations, 86 studies with 38,057 cattle herds from 42 countries on six continents were included in the meta-analysis. The global herd-level seroprevalence of C. burnetii in cattle was estimated to be 44.4% (95% confidence interval [CI], 37.9%-51.1%), with high heterogeneity among the included studies. The herd-level seroprevalence was significantly higher in dairy than in beef cattle herds (49.0% [95% CI: 41.9%-56.2%] vs. 14.5% [95% CI: 5.8%-32.1%], respectively). The global herd-level molecular prevalence of C. burnetii in cattle was estimated to be 32.3% (95% CI: 25.3%-40.01%), with high heterogeneity among the included studies. Herd-level molecular prevalence was significantly different among continents. The herd-level molecular prevalence ranged from 12.8% (95% CI: 7.1%-21.9%) in Asia to 70.0% (95% CI: 36.3%-90.5%) in North America. Regarding trends, the herd-level seroprevalence of C. burnetii in cattle did not change significantlyover the study years.

Conclusion: The global herd-level seroprevalence and herd-level molecular prevalence of C. burnetii in cattle were high, estimated at 44% and 32%, respectively. The herd-level seroprevalence trend did not significantly change over time. This result indicates that cattle remain a major reservoir host for C. burnetii and pose a potential risk to human health.