Understanding pathogen spillover

Amanda Budd, amanda.budd@uga.edu

Contact: Cecilia Sánchez, sanchez@ecohealthalliance.org

Network diagrams depicting the similarity between disciplines. Courtesy of Sanchez et al.

How different disciplines provide a holistic picture

A new study from the University of Georgia examines how different disciplines think about zoonotic spillover, the process of a pathogen transmitting from wildlife or livestock to infect humans. Because three quarters of emerging infectious diseases of humans start in animals, understanding how they can come to infect humans is critical.

The study, published in Zoonoses and Public Health, analyzed review papers across 10 disciplines, including veterinary science and molecular biology, and identified nine common mechanisms for pathogen spillover along with eight gaps in research.

Ecologists Cecilia Sánchez, Joy Vaz and John Drake from the Odum School of Ecology began the project to expand their own understanding of pathogen spillover and that of researchers in other disciplines.

Because pathogen spillover involves interactions among animals, humans, pathogens and the environment, perspectives from multiple disciplines are needed to understand its processes, which range from human behaviors that affect people’s exposure to wildlife to molecular mechanisms that control pathogen entry into host cells. Understanding these processes is important to inform efforts to prevent future outbreaks of infectious disease.

“We were thinking about how we can be sort of siloed in our respective academic disciplines and so the interest was, how do other disciplines outside of ecology think about the process of spillover and how diseases are transmitted?” explained Sánchez, now a research scientist with EcoHealth Alliance.

The researchers searched multiple databases for review papers discussing processes that allow pathogens to transmit from wildlife and livestock into humans. Using the 88 papers that met their search criteria, they identified more than 500 text segments that described spillover pathways. They consolidated these into nine clusters, or spillover processes: viral adaptation, climate and vectors, food and livestock, environmental contact, global movement, socioeconomics, agricultural land conversion, biodiversity and community, and reservoir hosts. Each process consisted of multiple interacting elements such as environmental change, host and pathogen traits, and human behaviors that create a favorable environment for cross-species transmission.

In addition to identifying common mechanisms of spillover, the researchers also pinpointed eight conceptual gaps where more knowledge or research was needed. These included areas such as identifying traits in pathogens that can raise the chance of cross-species transmission, and the effects of climate and weather on transmission risk.

The researchers also determined the discipline or disciplines to which each review paper belonged. The ten disciplines included those in the life sciences, social sciences, and public health, among others. As part of the study, the group mapped which disciplines were least and most similar in their content.

By pinpointing these similarities and differences, the researchers hope that their findings will be useful for directing interdisciplinary work and encouraging more collaboration across disciplines when looking at disease spillover.

Vaz noted that the gaps in understanding in certain fields highlighted by their research may be addressed by collaboration.

For example, they found that in veterinary science, review papers mentioned a lack of a complete understanding of viral adaptation as a mechanism of spillover, while in cellular and molecular biology, this is a better understood process.

“It could be that even though they’re doing very relevant research, there isn’t crosstalk between those disciplines,” Vaz said. “But if there was, we could really solve more problems or get more insight into what’s going on.”

This research was funded by the National Science Foundation and a President’s Seed Grant from the University of Georgia, and was a project of the Spillover Working Group of the UGA Center for the Ecology of Infectious Diseases.