Development of disease risk assessment on invasive alien species: evaluation of the risk of introduction of new infections and spread of local ones

Invasive alien species (IAS) represent one of the main global threats to biological conservation and can heavily affect human activities. To tackle this issue, the European Community has approved Regulation No 1143/2014 to define a common intervention line. According to it, a list of invasive alien species of Union concern has been defined and will be regularly updated in order to define priority interventions. Although infectious diseases have dramatic impacts on human health, economic sustainability of animal farming and biodiversity conservation, they are rarely included into evaluations due to the methodological complexities of their risk assessment. We used raccoon (Procyon lotor), coypu (Myocastor coypus) and grey squirrel (Sciurus carolinensis) as model species to develop a qualitative methodology for disease risk assessment that allows to assign each IAS’ pathogen into one out of four risk categories, depending on its impacts and the likelihood of the infection to occur. For each IAS we assessed the risk towards humans, domestic animals and wildlife relative to the introduction of new parasites and the amplification of local ones. Additionally we obtained a total disease risk evaluation for every species that included all these aspects. We also estimated the uncertainty level associated with each risk estimate to point out knowledge gaps. The hazard identification, carried through bibliographic review, identified 377 parasite species showing that raccoon is the IAS infected by the highest number of pathogens. The multiple outcomes produced by our approach showed that raccoon plays the highest risk of introduction and spreading of infections toward humans, livestock and wildlife. Moreover, it is the species with the highest uncertainty. This approach provides a method to explore whether alien species, with relatively low impact on biodiversity and human economy, might indeed entail high disease risks, underlining the importance to consider different aspects in the IAS risk assessment.