Highly pathogenic avian influenza in wild mammals: critical appraisal of spill-over events and of strategies for prevention, surveillance and preparedness

Recent years have seen an increase in spill-over events of Highly Pathogenic Avian Influenza (HPAI) to mammals, posing a significant public health threat. This report examines the epidemiological drivers behind these events, the clinical and pathological features observed in naturally infected mammals, and the strategies for surveillance, control, and prevention. The study focuses on wild mammals in different settings, including sylvatic environments, farms, and zoos/rescue centres, highlighting the complexity of HPAI transmission from birds to mammals and potentially between mammals. Key factors influencing spill-over include bird migration patterns, shared habitats, mammalian diet and behaviour, and environmental contamination. Carnivorous mammals, particularly juveniles, are more susceptible to HPAI, with predatory and scavenging behaviours identified as critical epidemiological drivers. Outbreaks in farmed and captive wildlife are often linked to inadequate biosecurity and contaminated feeding practices. Surveillance efforts should integrate passive and active components, focusing on high-risk populations, and be linked to bird and human surveillance to effectively monitor and mitigate HPAI outbreaks. Control measures require a thorough understanding of transmission mechanisms, with specific protocols needed for different environments. Prevention strategies should emphasise biosecurity, carcass management, and communication efforts to foster effective outbreak management and preparedness.