Zoonotic bacterial pathogens: antimicrobial resistance turns repeated animal exposure into a One Health threat

Zoonotic bacterial diseases cannot be understood simply as isolated spillover events from animals to humans. A new review argues that the real public-health risk is created by repeated exposure through livestock, food, water, soil, aerosols, vectors and contaminated environments, with antimicrobial resistance making these transmission networks increasingly difficult to control.

The review examines zoonotic bacteria from a One Health perspective, focusing on antimicrobial resistance, exposure pathways and control priorities. The authors stress that bacterial zoonoses differ from many viral threats: the main problem is often not a single species jump followed by human-to-human transmission, but the continuous maintenance of bacteria in animal populations and production environments.

Multiple pathways sustain human exposure

Humans may encounter zoonotic bacteria through direct animal contact, occupational exposure, contaminated meat or milk, water, soil, aerosols or arthropod vectors. This means that farms, slaughterhouses, food-processing environments and animal waste systems can all act as points of exposure. Wildlife and companion animals may also contribute depending on the pathogen and local ecology.

The review therefore places emphasis on the whole transmission system, rather than viewing infection only as a direct animal-to-human event.

AMR makes the problem more complex

Antimicrobial resistance adds another layer of risk because resistant bacteria and resistance genes can circulate between humans, animals and the environment. Use of antimicrobials in both human and veterinary medicine creates selective pressure, while manure, wastewater and contaminated environments can help resistant organisms persist and spread.

The result is a One Health problem in which controlling disease requires more than treating individual infections: surveillance must also monitor resistance patterns, reservoirs and routes of exposure.

Food systems remain central

Food-producing animals are particularly important because bacterial pathogens can enter the human population repeatedly through contaminated food chains. Unlike an outbreak caused by a newly emerging virus, bacterial zoonoses may persist silently within animal populations, with human infections appearing sporadically over long periods. This makes prevention at farm level, during slaughter and processing, and throughout food distribution particularly important.

Control requires integrated surveillance

The review argues for stronger coordination between veterinary, food-safety, environmental and human-health surveillance. Priorities include reducing unnecessary antimicrobial use, improving farm biosecurity, strengthening food hygiene, monitoring resistant bacteria in animals and environments, and integrating genomic surveillance across sectors.

The central message is that zoonotic bacterial risk is sustained by interconnected ecological and production systems. Effective control therefore depends not only on detecting human cases, but on identifying where bacteria are maintained, amplified and repeatedly transmitted before infection reaches people.