Infectious Disease Ecology: Effects of Ecosystems on Disease and of Disease on Ecosystems

Infectious Disease Ecology Effects of Ecosystems on Disease and of Disease on Ecosystems \ \ Princeton University Press \ Copyright © 2008 Princeton University Press\ All right reserved.\ ISBN: 978-0-691-12484-1 \ \ \ Introduction Felicia Keesing, Richard S. Ostfeld, and Valerie T. Eviner \ PATHOGENS ARE UBIQUITOUS. We are all familiar with the cold viruses that give us sniffles, coughs, and aches, and with the more frightening pathogens that cause diseases such as AIDS, malaria, and tuberculosis, which kill millions of people each year. But pathogens affect much more than our own health. Farmers struggle with fungi that attack their crops, managers of endangered species worry about the potential impact of an epidemic on the fragile populations under their stewardship, and tourists find their favorite snorkeling destinations devastated by coral bleaching diseases. Because of concerns like these, enormous quantities of energy and resources are deployed each year in the diagnosis and treatment of infectious diseases of humans, nonhuman animals, and plants. Yet annihilation of harmful pathogens is an unrealistic goal in most cases, and many other pathogens play critical positive roles in ecosystems, from recycling nutrients to increasing biological diversity. We are just beginning to recognize the degree to which pathogens, and the diseases they cause, are embedded within ecological systems.\ Infectious diseases necessarily involve interactions among at least two species, the pathogen and the host species itinfects. For many pathogens, such as the virus that causes avian flu, the fungus that causes soybean rust, and the protist that causes African sleeping sickness, more than one species can serve as a host. And many pathogens are transmitted from host to host by at least one species of vector, such as a mosquito, an aphid, or a tick. Understanding the dynamics of any particular disease system, then, involves understanding at best a simple but more often a complex system of interactions among the organisms most directly involved in disease transmission. Ecologists would seem to be natural allies of a suite of health specialists, including epidemiologists, physicians, veterinarians, and agricultural scientists.\ With notable exceptions, however, ecologists have not traditionally studied infectious diseases or have considered disease outbreaks as disturbances rather than inherent parts of the ecosystem. Similarly, most biomedical scientists have not considered the broader ecological contexts of disease. But the need to integrate these disciplines has become increasingly apparent in the past several years as we face a surge of emerging or reemerging infections, including West Nile virus encephalitis, sudden oak death, severe acute respiratory syndrome (SARS), monkeypox, and new types of avian influenza. Typically, a newly emerging infectious disease is recognized from a cluster of mysterious disease cases arising in a host population, followed by the elimination of well-known pathogens as potential causes, and finally the identification of a new pathogen, or perhaps of an old one outside its known range. Remedial action is then undertaken to prevent further spread of the disease. When the pathogen is specialized-that is, largely restricted to one host species-and is transmitted directly between individuals, the standard public health arsenal to battle disease-quarantine, vaccination, emergency public education-is usually effective. SARS is a recent example. However, when the pathogen is more generalized, infecting multiple host species, including asymptomatic reservoirs, or when it is transmitted indirectly, such as by vectors or through environmental contact, then remedial action is much more problematic, and outbreaks may be followed by poorly contained spread, often with devastating consequences. Recent examples of poorly contained outbreaks include West Nile virus in humans, horses, and wild birds; sudden oak death in live oaks and tanoaks; Ebola virus in humans and apes; Lyme disease in humans; hantavirus pulmonary syndrome in humans; and various transmissible spongiform encephalopathies in livestock, wildlife, and humans. Failure of the standard biomedical arsenal in the cases of some human, nonhuman animal, and plant diseases may be largely a consequence of the ecological complexity involved in the evolution, transmission, and maintenance of these pathogens in nature.\ Other lines of evidence also suggest that a more ecological perspective would greatly enhance our understanding and management of diseases. For example, more than 75% of emerging human pathogens are zoonotic (Taylor et al. 2001), that is, they are transmitted to humans from other animals. This observation suggests that a focus on the ecological interactions between wildlife hosts and zoonotic pathogens would be fruitful. Climate change has been associated with an increase in the frequency, distribution, and severity of many infectious diseases worldwide (Harvell et al. 2002), demonstrating ecological impacts on pathogen dynamics. And the rapid spread throughout Eurasia and Africa of the H5N1 strain of avian flu virus highlights just how much we need to know about bird migration patterns to develop appropriate management strategies for a potential human pandemic (Olsen et al. 2006). Some recent studies attest to the ability of ecological approaches to inform disease prevention and management. For example, the number of Lyme disease cases can be predicted almost two years in advance simply by monitoring annual acorn production (Ostfeld et al. 2006), allowing early, targeted public warnings. As another example, planting a diversity of rice strains rather than a monoculture has been shown to increase yields and reduce rates of infection with fungal rice blast in China (Zhu et al. 2000). More and more case studies like these are being published every year.\ There are, in our view, two pressing needs if we are to improve our ability to predict the occurrence, dynamics, and consequences of infectious diseases. The first and most obvious need is to forge stronger alliances between ecologists and the traditional infectious disease specialists. Biomedical, veterinary, and agricultural scientists are well equipped to track infectious disease in populations and to treat and attempt to prevent disease in individual patients or populations. The power of these disciplines to improve the quality of life for people and other animals is enormous. Nevertheless, these disciplines often are not well equipped to anticipate disease outbreaks or to track the consequences of diseases beyond direct effects on victim populations. We see a strong role for ecologists in both these endeavors. Assembling the conceptual expertise is only part of the challenge, however: disease biologists from all disciplines need to work together more effectively to integrate knowledge of the functioning of ecological systems with knowledge of pathogens, cells, tissues, and immune systems and to develop effective management strategies based on this integration.\ The second need is to identify the general ecological principles that underlie the dynamics of disease systems. Case studies now exist in sufficient number to allow the vigorous pursuit of conceptual syntheses. Such syntheses would provide a crucial unification of many disparate diseases and provide guidance for researchers attacking new disease systems. We know, for example, that some hosts are more efficient at transmitting particular pathogens than others, but what generalities, if any, can be made about the role of host diversity in disease transmission? Habitat fragmentation has been shown to affect the transmission of malaria in Brazil (Vittor et al. 2006), Lyme disease in New York and New England (Allan et al. 2003; Brownstein et al. 2005), and hantavirus in Panama, but do we know enough to be able to predict the impact of habitat fragmentation-and perhaps other forms of habitat alteration- on other diseases? Are some types of pathogens more likely than others to affect ecosystem functioning, and similarly, are some ecosystems more vulnerable to the impacts of pathogens? Under what conditions do infectious diseases alter the functioning of ecological systems in desirable ways, by, for example, increasing the cycling rates of nutrients or increasing biological diversity?\ This book attempts both to develop conceptual frameworks and to more fully integrate ecology with traditional disease biology. We have invited outstanding scientists and educators to provide conceptual syntheses of their areas of expertise. We have organized these efforts into three main sections. The first focuses on the effects of ecosystems, in the broadest sense, on infectious diseases, the second on the effects of infectious diseases on ecosystems, and the third on management and applications using these ideas. In an effort to foster the developing dialogue among scientific specialties, we have included contributions from ecologists, biomedical scientists, agricultural scientists, and veterinarians.\ The contributions in this book exhibit a three-pronged conceptual approach. They articulate the generalities emerging from the increasing number of case studies appearing in the scientific literature, raise specific questions to guide future studies, and demonstrate both the challenge and the potential for ecologists and other disease biologists to work together. Owing to increased interest, particularly on the part of young scientists, and to rising levels of funding, opportunities to study the ecology of infectious disease are increasing. From higher agricultural yields to more diverse animal communities to reduced human suffering and mortality, we have much to gain from the marriage of ecology and disease biology.\ (Continues...)\ \ \ \ \ Excerpted from Infectious Disease Ecology\ Copyright © 2008 by Princeton University Press . Excerpted by permission.\ All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.\ Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site. \ \

Acknowledgments     ixList of Contributors     xiIntroduction   Felicia Keesing   Richard S. Ostfeld   Valerie T. Eviner     1Effects of Ecosystems on DiseaseIntroduction   Felicia Keesing     9Effects of Host Diversity on Disease Dynamics   Michael Begon     12The Role of Vector Diversity in Disease Dynamics   Alison G. Power   Alexander S. Flecker     30Understanding Host-Multipathogen Systems: Modeling the Interaction between Ecology and Immunology   Pejman Rohani   Helen J. Wearing   Daniel A. Vasco   Yunxin Huang     48Influence of Eutrophication on Disease in Aquatic Ecosystems: Patterns, Processes, and Predictions   Pieter T. J. Johnson   Stephen R. Carpenter     71Landscape Structure, Disturbance, and Disease Dynamics   Hamish McCallum     100Effects of Disease on EcosystemsIntroduction   Valerie T. Eviner     125Effects of Disease on Keystone Species, Dominant Species, and Their Communities   Sharon K. Collinge   Chris Ray   Jack F. Cully, Jr.     129Red Queen Communities   Keith Clay   Kurt Reinhart   Jennifer Rudgers   TammyTintjer   Jennifer Koslow   S. Luke Flory     145Invasion Biology and Parasitic Infections   Sarah E. Perkins   Sonia Altizer   Ottar Bjornstad   Jeremy J. Burdon   Keith Clay   Lorena Gomez-Aparicio   Jonathan M. Jeschke   Pieter T. J. Johnson   Kevin D. Lafferty   Carolyn M. Malmstrom   Patrick Martin   Alison Power   David L. Strayer   Peter H. Thrall   Maria Uriarte     179Effects of Disease on Community Interactions and Food Web Structure   Kevin D. Lafferty     205Is Infectious Disease Just Another Type of Predator-Prey Interaction?   Spencer R. Hall   Kevin D. Lafferty   James M. Brown   Carla E. Caceres   Jonathan M. Chase   Andrew P. Dobson   Robert D. Holt   Clive G. Jones   Sarah E. Randolph   Pejman Rohani     223Microbial Disease in the Sea: Effects of Viruses on Carbon and Nutrient Cycling   Mathias Middelboe     242Effects of Pathogens on Terrestrial Ecosystem Function   Valerie T. Eviner   Gene E. Likens     260Disease Effects on Landscape and Regional Systems: A Resilience Framework   F. Stuart Chapin III   Valerie T. Eviner   Lee M. Talbot   Bruce A. Wilcox   Dawn R. Magness   Carol A. Brewer   Daniel S. Keebler     284Research Frontiers in Ecological Systems: Evaluating the Impacts of Infectious Disease on Ecosystems   Sharon L. Deem   Vanessa O. Ezenwa   Jessica R. Ward   Bruce A. Wilcox     304Management and ApplicationsIntroduction   Richard S. Ostfeld     321The Community Context of Disease Emergence: Could Changes in Predation Be a Key Driver?   Robert D. Holt     324The Emergence of Wildlife Disease and the Application of Ecology   Peter J. Hudson   Sarah E. Perkins   Isabella M. Cattadori     347Applied Biodiversity Science: Managing Emerging Diseases in Agriculture and Linked Natural Systems Using Ecological Principles   K. A. Garrett   C. M. Cox     368The Ecology of an Infectious Coral Disease in the Florida Keys: From Pathogens to Politics   James W. Porter   Erin K. Lipp   Kathryn P. Sutherland   Erich Mueller     387Infection and Ecology: Calomys callosus, Machupo Virus, and Acute Hemorrhagic Fever   Karl M. Johnson     404Resolved: Emerging Infections of Humans Can Be Controlled by Ecological Interventions   C. J. Peters      423From Ecological Theory and Knowledge to Application   James E. Childs     441Educating about Infectious Disease Ecology   Carol A. Brewer   Alan R. Berkowitz   Patricia A. Conrad   James Porter   Margaret Waterman     448Concluding Comments: Frontiers in the Ecology of Infectious DiseasesThe Ecology of Infectious Diseases: Progress, Challenges, and Frontiers   Richard S. Ostfeld   Felicia Keesing   Valerie T. Eviner     469Index     483

\ Ecology\ - Mark L. Wilson\ One exciting aspect of this book is that 'ecologists' and 'epidemiologists' and 'microbiologists' and 'botanists' and various other scholars were brought together to share ideas, data, and inferences. This volume reflects such interdisciplinary exchange, and more interactions like this are sorely needed. . . . It is highly recommended as a useful set of readings for ecologists interested in disease-causing microbes, and for epidemiologists seeking understanding of the ecosystem interactions that affect infectious agent transmission.\ \ \ \ \ BioScience\ - Gregory E. Glass\ Infectious Disease Ecology provides new and useful insights that expand upon earlier works in the field.\ \ \ Journal of Archaeological Science\ - Holger Schutkowski\ [T]his is an enormously useful book which, for the first time, brings together a wide range of disciplinary expertise under the umbrella of a comprehensive, integrated approach towards understanding the interrelationship between disease and ecology. . . . This book is tremendously recommendable. It provides comprehensive cutting edge insights into the fascinating interplay of the proximate and ultimate forces that shape the host-pathogen race. . . . It will be the standard for some time to come.\ \ \ \ \ Quarterly Review of Biology\ - A. Townsend Peterson\ Overall, the book is quite strong, and offers useful and thorough overviews, a difference from the usual reworks and overviews that pervade edited volumes—in this sense, the editors are to be congratulated. . . . [T]his book is a useful picture of the state of the field, and could be a basis for graduate-level seminars treating the field of disease ecology.\ \ \ \ \ EcologyOne exciting aspect of this book is that 'ecologists' and 'epidemiologists' and 'microbiologists' and 'botanists' and various other scholars were brought together to share ideas, data, and inferences. This volume reflects such interdisciplinary exchange, and more interactions like this are sorely needed. . . . It is highly recommended as a useful set of readings for ecologists interested in disease-causing microbes, and for epidemiologists seeking understanding of the ecosystem interactions that affect infectious agent transmission.\ — Mark L. Wilson\ \ \ \ \ BioScienceInfectious Disease Ecology provides new and useful insights that expand upon earlier works in the field.\ — Gregory E. Glass\ \ \ \ \ Journal of Archaeological Science[T]his is an enormously useful book which, for the first time, brings together a wide range of disciplinary expertise under the umbrella of a comprehensive, integrated approach towards understanding the interrelationship between disease and ecology. . . . This book is tremendously recommendable. It provides comprehensive cutting edge insights into the fascinating interplay of the proximate and ultimate forces that shape the host-pathogen race. . . . It will be the standard for some time to come.\ — Holger Schutkowski\ \ \ \ \ Quarterly Review of BiologyOverall, the book is quite strong, and offers useful and thorough overviews, a difference from the usual reworks and overviews that pervade edited volumes—in this sense, the editors are to be congratulated. . . . [T]his book is a useful picture of the state of the field, and could be a basis for graduate-level seminars treating the field of disease ecology.\ — A. Townsend Peterson\ \