New paper led by biology professor Bard Felicia Keesing calls for more rigorous study of dilution effects in natural ecosystems to better understand infectious disease ecology


Biology professor Bard Felicia Keesing conducts fieldwork on tick-borne diseases in Laikipia district of Kenya

The COVID-19 pandemic has highlighted the global importance – and the challenge – of understanding the ecology of infectious diseases, particularly with regard to the impact of biodiversity on the transmission of zoonotic diseases. A new paper in Ecology letters co-authored by biology professor Bard Felicia Keesing and Rick Ostfeld, a disease ecologist at the Cary Institute of Ecosystem Studies, argues that one of the keys to improving this understanding is a more rigorous and creative study of the dilution effects, which occur when the diversity of an ecological community decreases the transmission of the disease. Dilution effects have been used for decades to manage the transmission of parasites and pathogens in plants, animals and humans.

“The impacts of diversity on the emergence and transmission of pathogens have never been more relevant,” write Keesing and Ostfeld in their article, “Dilution Effects in Disease Ecology”. “Over the past 20 years, attention has focused on whether the patterns that can occur – when someone chooses which organisms are present in a system – ever occur naturally, as diversity changes. under natural conditions This is a particularly important issue because the diversity within natural ecosystems changes rapidly in response to human impacts such as habitat fragmentation, overexploitation, pollution and climate change.

In their article, Keesing and Ostfeld discuss how and where dilution effects have been used to manage infectious diseases. “We explore the ecological mechanisms underlying these effects, then turn to more recent questions: whether dilution effects occur in natural communities, and if so, whether these effects are impacted by changes in biodiversity. natural, ”they write. “We review the evidence for when and how often natural dilution effects occur, describe some of the challenges of studying them, and describe common misapplications of the concepts, as well as important unresolved questions.”

Keesing and Ostfeld write that the analyzes reveal that natural dilution effects are common, but that their study remains difficult “due to limitations in the ability of researchers to experimentally manipulate many disease systems, difficulties in acquiring data on host quality and confusion over what should and should not be considered a dilution effect. Important questions for future research, they write, include: “Does the pattern of variation in host quality predictably vary for different metrics (e.g., reservoir competence, vector preference? ) and according to the types of pathological systems? How do interactions within hosts affect dilution effects in multi-pathogenic systems? What is the frequency of positive relationships between ecological resilience and host quality? What are the forms of these relationships when they occur, and what are their underlying causes? What are the best metrics for measuring transmission between disease systems? What are the characteristics of natural disease systems that exhibit dilution effects and which do not, and what does this suggest about whether we could apply our understanding of dilution effects to manage disease? in nature ? “

Keesing and Ostfeld conclude that there is much to learn about the relationship between change in biodiversity and the emergence of pathogens, and that further study of dilution effects will be essential. “Important questions include how biodiversity, and its loss, affects the emergence of pathogens from non-human hosts; how we can effectively determine whether hosts can actually transmit pathogens, instead of just being infected by them; and how to manage our behavior and use of landscapes to minimize spillover events, ”they write. “Recognizing what we have learned about dilution effects in nature over the past 20 years is of critical importance, as is understanding their similarities and differences to the dilution effects that operate in water systems. disease management such as agricultural fields. “

To read the full article in Ecology Letters, click here.

This research was funded by a grant from the National Science Foundation OPUS 1948419 in Keesing.

Felicia Keesing, David and Rosalie Rose, Emeritus Professor of Science, Mathematics and Computer Science, has been on Bard’s faculty since 2000. She holds a BS from Stanford University and a PhD. from the University of California, Berkeley. Since 1995, she has been studying the functioning of African savannas when large charismatic animals such as elephants, buffaloes, zebras and giraffes disappeared. She is also studying how interactions between species influence the likelihood of humans being exposed to infectious diseases. Keesing is also studying Lyme disease, another disease transmitted by ticks. She is particularly interested in how species diversity affects disease transmission. Most recently, she has focused on science literacy for students and she has led the overhaul of the Citizen Science program at Bard College. Keesing has received research grants from the National Science Foundation, the National Geographic Society, the National Institutes of Health, the Environmental Protection Agency, and the Howard Hughes Medical Institute, among others. She received the United States Presidential Early Career Award for Scientists and Engineers (2000). She is co-editor of Ecology of infectious diseases: effects of ecosystems on diseases and diseases on ecosystems (2008) and has contributed to publications such as Nature, Science, Proceedings of the National Academy of Sciences, Ecology letters, Emerging infectious diseases, Acts of the Royal Society, Ecology, Biosciences, Conservation biology, and Trends in ecology and evolution, among others.

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Publication date : 09-08-2021


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