Public and animal health risks associated with spillover of Brucella melitensis into dairy farms

Brucellosis is a worldwide zoonosis with important public health, animal health and economic implications. Brucella melitensis, commonly associated with small ruminants, is an emerging bovine pathogen in dairy farms. We analysed all B. melitensis out-breaks affecting dairy farms in Israel since 2006, combining traditional and genomic epidemiology to explore the public health implications of this One Health challenge. Whole-genome sequencing was applied to bovine and related human B. melitensis isolates from dairy farm outbreaks. cgMLST- based and SNP -based typing was integrated with epidemiological and investiga-tion data. A secondary analysis combining the bovine -human isolates with endemic human isolates from southern Israel was performed. A total of 92 isolates from dairy cows and related human cases originating from 18 epidemiological clusters were analysed. Most genomic and epi-clusters were congruent, but sequencing showed relatedness between apparently unrelated farm outbreaks. Nine secondary human infections were also genomically confirmed. The bovine -human cohort appeared inter-mixed with 126 endemic human isolates in southern Israel. We show a persistent and widespread circulation of B. melitensis in dairy farms in Israel with secondary occupational human infection. The genomic epidemiology also uncovered cryptic con-nections between outbreaks. A regional connection between bovine and endemic human brucellosis cases points to a common reservoir, most probably local small ruminant herds. Control of humans and bovine brucellosis is inseparable. Epidemiological and microbiological surveillance and implementation of control measures across the entire range of farm animals is needed to mitigate this public health challenge.

Automated summary

Brucellosis, a global zoonotic disease, poses significant public health, animal health, and economic challenges. A study in Israel analyzed Brucella melitensis outbreaks in dairy farms since 2006 and used genomics to explore the implications of this One Health issue. Genomic sequencing revealed connections between seemingly unrelated outbreaks and confirmed secondary human infections. The study also identified a regional connection between bovine and endemic human brucellosis cases, suggesting a common reservoir in local small ruminant herds.