BioOne.org will be down briefly for maintenance on 12 February 2025 between 18:00-21:00 Pacific Time US. We apologize for any inconvenience.
Open Access
How to translate text using browser tools
1 March 2009 Big Fleas Have Little Fleas
Gregory E. Glass
Author Affiliations +

Infectious Disease Ecology: Effects of Ecosystems on Disease and of Disease on Ecosystems consists principally of presentations given at the 2005 Cary Conference on the ecology of infectious diseases, held at the Cary Institute for Ecosystem Studies in Millbrook, New York. The book includes chapters on nearly all of the presentations made during the three-day meeting, as well as a few additional chapters, and captures the twofold intent of the original symposium: (1) to emphasize the ecological complexity in the evolution, transmission, and maintenance of pathogens and (2) to further the field's development by merging disease studies with community and ecosystem studies. Infectious Disease Ecology provides new and useful insights that expand upon earlier works in the field, notably B. T. Grenfell and A. P. Dobson's Ecology of Infectious Diseases in Natural Populations (Cambridge University Press, 1995), published 13 years ago.

Richard Ostfeld, a senior scientist at the Cary Institute, has for years studied the relationships between biodiversity and disease ecology. Felicia Keesing is an associate professor at Bard College in New York who focuses on the impacts of species interactions on community structure. Valerie Eviner is an assistant professor at the University of California, Davis; her expertise in ecosystems and landscape ecology in plant sciences provides an important perspective missing from most books on infectious diseases that focus exclusively on humans and other animals.

The purpose of the 2005 Cary Conference was to improve our ability to forecast the occurrence, dynamics, and impacts of infectious diseases, because despite researchers' greater focus on changing patterns of infectious diseases during the past two decades, the record for anticipating outbreaks is still poor. Better forecasting can be accomplished by building better relationships between ecologists and more traditional infectious disease specialists, and by better identifying the general ecological principles influencing the dynamics of disease systems. Infectious Disease Ecology captures the essence of attempts to reach these goals and is a successful contribution at various levels. The book keeps the flavor of the formal presentations as well as that of the critical, informal discussions. For people interested in the history of this field, it will be important reading not only because of what it says but also because of its demonstration of the challenges of merging two diverse approaches to problem solving. Although those two approaches are complementary, each faces constraints in how they dealt with key research issues.

f01_263.eps

At a basic level, the book is a good overview of the ecological perspective on infectious diseases. After largely ignoring the field for several decades, traditional ecologists have in recent years begun to consider these as systems of interacting agents. Chapters that are predominantly theoretical keep the details of the analyses to a minimum and concentrate on providing a conceptual rationale for the results. These will be especially appealing to readers who seek an intuitive understanding of the approaches or who need a framework for their research program. In addition, many chapters have a descriptive emphasis, characterizing general properties of infectious diseases in both plants and animals. The inclusion of plant pathogens and aquatic ecosystems— especially Mathias Middelboe's chapter about the impacts of viruses on carbon and nutrient cycling in the ocean—is a wonderful benefit for those want a broad overview of host-pathogen interactions.

The first two of the book's four major sections represent nearly two-thirds of the volume. The first explores how ecosystem structure influences patterns of disease, presenting some of the more intriguing perspectives in the book by placing infectious processes within a community and landscape structure and moving beyond simple dyadic interactions. The second section, no less engaging, considers how diseases affect the structure and function of ecosystems. It includes Middelboe's chapter, as well as one by Spencer R. Hall and colleagues that looks at the conditions under which we can recast host-parasite dynamics in terms of familiar predator-prey systems.

The third section considers the management and applications of disease ecology to public health, education, and control of emerging diseases. This section includes chapters that will provide a basis for research programs for the next several years. The final section is a single chapter, written by the editors, that summarizes the volume and provides their vision of how disease ecology currently fits within the framework outlined in the introduction. It also suggests where the field needs continued development.

The book generally works well. If it has a shortcoming, I suspect that it lies in the ambitiously declared first goal of the conference—improving relationships between ecologists and more traditional infectious disease specialists. This is a critical and needed step. If ecologists really want to understand the tension between themselves and “traditionalists,” they should read the chapter by James E. Childs, who uses the recent foot-and-mouth disease outbreak in the United Kingdom as a case study, before they read the remainder of the book. With two short quotations, he shows just how far apart the two fields are. They demonstrate the wide divergence between what infectious disease ecologists claim they contributed and what an influential part of the veterinary community believes was added. This divide spills over, not surprisingly, even into terminology. The use of “disease,” a phenotypic expression of infection, by ecologists makes an epidemiologist cringe. Interchanging prevalence and incidence—two quite different measures of infection—generates a similar reaction.

The two remaining chapters in this arena, by Karl M. Johnson and C. J. Peters, present fairly typical, descriptive overviews of disease systems in the form of case studies. Characterizing them as descriptive is not pejorative; they do capture the approach of traditional studies, in which there are typically a small number of pathogens whose actions and effects are summarized. What is evident from these chapters is just how better supported by data the descriptions of these specific systems are than those of most plant and animal systems. Consequently, we are left to wonder what would happen if epidemiologists applied ecological modeling to their systems. Sadly, this question wasn't addressed by the conference, and it would have been informative to include some epidemiologic modelers. After all, as early as the late 1960s and early 1970s, this group had conducted stochastic simulations of epidemics, characterized threshold population sizes, and evaluated intervention scenarios for disease outbreaks. This work was quite close to that of the ecological modelers at the conference.

The evolution of public health modeling away from these approaches would have been a useful adjunct to clarifying how the fields developed and how they might come together. As the editors note in the final chapter, however, ecologists face a challenge in finding ways to build conceptual-theoretical models that will be useful to human systems, not because they are inherently different but because the medical research community has different expectations. In that regard, the integration of ecological modeling with human diseases has shown tremendous progress in the years since the conference, which vindicates the editors' hopes. The creation of large-scale modeling efforts, whether focusing on strictly human diseases such as syphilis, gonorrhea, malaria, and measles, or pandemics of spillover pathogens such as avian influenza, demonstrates the tremendous vitality and growth of the field.

Gregory E. Glass "Big Fleas Have Little Fleas," BioScience 59(3), 263-264, (1 March 2009). https://doi.org/10.1525/bio.2009.59.3.11
Published: 1 March 2009
Back to Top