Why this matters: Case definitions are regularly used in human medicine and with certain domestic animal diseases of concern, but less commonly in wildlife. The consistent use of diagnostic case definitions among pathologists and across institutions forms a necessary foundation for data sharing because they provide a common understanding of the basis for the diagnosis.

There are multiple ways to reach a diagnosis, some of which have a higher degree of certainty than others. A case definition provides a standardized, science-based set of criteria for diagnosing disease and pathogens that includes an assessment of diagnostic certainty. Based on the information available for individual, place, time, history, clinical signs, diagnostic observations, and diagnostic test results, specimens and samples are classified as “confirmed,” “presumptive,” or “suspected” when diagnosing a specific disease or “exposed” or “present/detected” for detecting a pathogen or toxin.

The USGS and CWHC Case Definition Joint Working Group produced a template and instructions for drafting new case definitions that is available as a fillable Word document. Creating the template and case definitions was a collaborative process involving the joint working group and pathologists at both institutions. The documents were then peer-reviewed as part of the USGS Techniques and Methods publication process. Case definitions have now been published for avian botulism, electrocution, snake fungal disease, Stony Coral Tissue Loss Disease, and West Nile virus. The NWHC-CWHC working group has additional draft case definitions in process, including avian cholera, distemper, chronic wasting disease, aspergillosis, brucellosis, duck virus enteritis, and lead poisoning. The template and all published case definitions are available online. Case definitions will be periodically reviewed and updated to incorporate new scientific techniques and information as needed.

The NWHC-CWHC working group would like to acknowledge the generous collective input and expertise of the staff, pathologists, students, and colleagues at both institutions and other additional contributors, as well as the USGS Science Publishing Network for guidance in the development of these case definitions.