Because One Health is, by definition, a multidisciplinary topic, it is difficult to identify one or two "best" databases to search. Instead, it will depend very much on what topic you are searching for, and what aspects of that topic you are interested in. Here are some databases which are likely to help you when searching for material from various disciplines, but this is not an exhaustive list. There are several databases listed for each area; each covers a different selection of the journals published in that discipline, so often you will want to search more than one database so that you can do a more thorough search.
If you do not find the information you need, please feel free to get in touch with the One Health liaison librarian. Her contact information is on the home tab of this guide.