Zoonotic Disease Classification in Wildlife: A Theoretical Framework for Researchers

1. Classification systems are useful tools for aggregating diseases to study them in more detail. The most widespread system for the classification of human diseases is the International Classification of Diseases (ICD), however the ICD was designed for use in health care and fails to capture many details of zoonotic diseases as a result.
2. We propose a framework for zoonotic disease classification which combines four known classification types (pathogen type, life cycle, transmission direction and habitat) into one systematic method. We chose to focus on four specific aspects to provide as broad an overview as possible of zoonoses to inform the risk of transmission to humans.
3. This framework can be applied to the zoonoses occurring in any animal species and lead to the generation of systematically collected empirical data useful for monitoring of zoonosis spatio-temporal dynamics.
4. To demonstrate the utility of our framework, we focus on deer species that are widespread in Eurasia; Red (Cervus elaphus), roe (Capreolus capreolus), fallow (Dama dama), sika (Cervus nippon), muntjac (Muntiacus reevesi) and Chinese water deer (Hydropotes inermis). We then examined the worldwide occurrence and prevalence of zoonoses in these species through a scoping review of the literature.
5. Altogether, 996 records of zoonotic diseases in wild deer, from 431 peer-reviewed papers, and 120 zoonotic pathogens were found. Within deer populations the most prevalent zoonoses were bacterial, while the most prevalent life cycles were metazoonoses. We also found that the most prevalent pathogens in deer were those with hosts capable of occupying sylvatic, peridomestic and domestic habitats.
6. Baseline data generated using this method can provide important starting points for making projections of human disease risk, assisting wildlife managers in making wildlife management decisions and assisting experts in the development of disease monitoring and management plans.