Links between emerging infectious diseases and global food production
The global human population is projected to reach 11 billion by 2100. How can we address the need to sustainability feed the planet while limiting the emergence and spread of human infectious diseases?
Agricultural practices must shift to support changing and increasing food demand. But how will such changes in global agriculture influence the emergence and spread of global infectious diseases? How can we achieve a more sustainable food system while also making progress towards reducing communicable diseases? To answer these questions, we assembled a team of ecologists, epidemiologists, agricultural scientists, and others who work on one or more aspects of agricultural and food systems and infectious disease transmission. It is widely acknowledged across each of our scientific disciplines that agricultural systems and practices have broad impacts on ecosystem and public health, and vice versa, but we found no comprehensive synthesis of the infectious disease risks and benefits associated with agricultural expansion and intensification. Our recently published work in Nature Sustainability offers key insights into how we can achieve a sustainable food system while also making progress towards reducing infectious diseases.
Our team learned three important lessons as we assessed the evidence for relationships between agriculture and infectious disease transmission. First, research at this interface is furthest along and has achieved the greatest theoretical, observational and experimental rigor in the area of nutrition and infectious disease, mainly through biomedical and clinical research. Many direct, within-host interactions between nutrition status and susceptibility and progression of infectious diseases have been recognized, studied and acted upon for many decades, resulting in the clear delineation and characterization of specific mechanisms, and paving the way for integrated interventions linking food, nutrition and infectious disease control.
Second, while direct, within-host interactions between nutrition status, immunity and infection are generally well understood, many indirect and bidirectional pathways linking agricultural and food systems to infectious disease transmission have been understudied, and these generally require systems-level description, formalization and analysis. Examples include situations where—as nutrition improves—certain parasites might proliferate faster than immunity can increase, resulting in more, rather than less, morbidity; where parasitic infections place direct demands on host nutrition, compromising resistance and tolerance to future infections; and where increasing high-density, industrialized animal agriculture operations yield greater global vulnerability to livestock infections, potentially devastating losses of animals to disease (e.g., highly pathogenic avian influenza, foot and mouth disease), and the resistance consequences of increasing antimicrobial use at nontherapeutic doses. Understanding interactions between agricultural and infectious disease systems across the relevant scales—e.g., from molecular in the spread of antimicrobial traits, to the global in the proliferation of confined animal feeding operations—requires multiple levels of analysis, and defies description, let alone robust analysis, by any one disciplinary approach. We argue for future studies that are capable of capturing these multi-scale interactions, feedbacks and dynamics, and the transdisciplinary expertise needed to rigorously carry them out.
Third, because agricultural and pathogen dynamics arise from inherently complicated, multi-species systems that exhibit interactions at many levels, sophisticated quantitative modeling approaches will be necessary to achieve improved understanding, develop sound theory, and design appropriate solutions. Modeling approaches will be critical for evaluating—and projecting into future decades—the risks and benefits that accompany the complex web of interactions between agricultural systems, social dynamics, and infectious diseases. Here, our disciplines share significant common ground—and thus a head start on interdisciplinary collaboration—in that mathematical modeling of complex systems has a long history of advancement and application in ecology, pest management, agricultural economics, and infectious disease epidemiology alike. We see considerable opportunity for innovation in the years to come, establishing models that will provide the means to evaluate and balance efforts to expand agricultural systems, achieve social benefits, and reduce infectious disease risk.
Collaborations such as ours are ready to put modeling, agroecology, field experiments, epidemiologic designs, and other approaches to work to sustainably improve human nutrition while controlling infectious diseases. We cite exciting developments and signs of progress, including efforts to enforce global regulations to cap antimicrobial use, enhance education and health literacy with regards to nutritional guidelines and meat consumption, and leverage agricultural development to escape poverty traps associated with infectious diseases. We are made hopeful by efforts to vigorously assess the degree to which biodiversity conservation can prevent zoonotic disease spillover and emergence, and recent advances to improve and diversify plant and animal genetic material to resist pests and other stressors with fewer chemical inputs. Still, our authorship team argues for the need to vigorously target structural aspects of these global problems, by investing in family planning, promoting education and employment opportunity among women, enhancing early childhood survival, and reducing income inequality. Such investments would not only improve health and quality of life among those most vulnerable, but also yield resource conservation and protection for future generations.
Justin Remais, Karena Nguyen and Meggan Craft