A scoping review of One Health interventions 2005-2025: What has been done, are they effective, and what are the best...

One Health research and practice are evolving rapidly, necessitating solid evidence-building and quality assessment of One Health interventions. We conducted a scoping review to (1) characterize how many and what kinds of One Health interventions are published in peer-reviewed literature; and (2) assess whether the identified interventions demonstrated effectiveness. We hypothesized that the evidence was limited in numbers and ability to demonstrate effectiveness.

The review was reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews. The initial search was conducted on Medline (Ovid), Embase, PubAg, and Web of Science in May 2024 and updated in December 2025. Inclusion criteria were: Primary research in which the investigators intervened with humans, animals, or their shared environment (at least two of three domains); an outcome assessment was included, and full text was available in English, published on or before December 16, 2025. Two researchers independently screened and analyzed all manuscripts.

Over 18,000 references were screened, and 151 studies were included. Studies were conducted in 53 countries representing all six WHO Regions. The highest number of interventions were reported from the United States of America, Tanzania, and India. Among 79 interventions that targeted zoonoses, the most common diseases were general zoonoses, rabies, and cysticercosis. Over half (55%) of the study designs were quasi-experimental, followed by 23% randomized control trials (RCTs) and 19% non-randomized experiments. Less than half (41%) of the studies had a control or comparison group. The most common perceived sources of bias were immigrative (28%) and emigrative selection bias (11%). Eight field-based RCTs identified that a One Health intervention was effective in reducing disease occurrence or pathogen detection compared to the control. Exemplary practices included a comprehensive intervention spanning human, animal, and environmental domains, using a participatory approach, assessing longer-term outcomes, triangulating results using more than one method, not overstating findings, and providing a visual aid to describe the intervention.

A small number of field-based RCTs clearly demonstrated the comparative effectiveness of One Health interventions, while it was challenging to assess the effectiveness of other studies without a more granular definition of effectiveness. Rigorous studies that assess the effectiveness of One Health interventions will collectively improve buy-in from governments, researchers, and policymakers, and advance the evidence base for employing the One Health approach.