Integrating zoonotic pathogen spillover risk into Life Cycle Assessment: Probabilistic method development for chicken farming

Abstract

Animal agriculture contributes substantially to the risk of emerging zoonotic diseases, which are an environmental and human health risk not captured by current life cycle assessment (LCA) methods for animal products. Furthermore, new value chains in the bioeconomy are emerging to valorize sidestreams from the farmed animal industry, such as using feathers for protein-based materials, potentially leading to changing pathogen exposures. Methods for assessing the risk of zoonotic pathogen spillovers across the life cycle of animal agriculture are thus critically needed. We present a conceptual framework for the life cycle risk of zoonotic pathogen spillovers in industrial-scale chicken production, based around the spillover risk at each stage of chicken production (i.e., breeding, hatching, grow-out, processing, and sidestream valorization). We develop an initial semi-quantification for the spillover risk of avian influenza at the grow-out stage in two key chicken producing countries (Brazil and the United States) utilizing event tree modelling. Our preliminary findings suggest spillover risk at the grow-out stage is higher in the US than Brazil, owing in part to a larger presence of migratory bird species (key reservoirs of avian influenza). Additional research is necessary to quantify risk distributions for other production stages and develop methods for allocating spillover risks (especially to emerging valorization of sidestreams). Incorporating the risk of zoonotic pathogen spillovers into animal product LCA - as has been done for e.g., greenhouse gas emissions and land use - would help inform policymakers and consumers regarding the impacts of dietary choices and contribute to international One Health goals.