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Infectious Disease Ecology

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

Richard S. Ostfeld
Felicia Keesing
Valerie T. Eviner
Copyright Date: 2008
Pages: 504
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  • Book Info
    Infectious Disease Ecology
    Book Description:

    News headlines are forever reporting diseases that take huge tolls on humans, wildlife, domestic animals, and both cultivated and native plants worldwide. These diseases can also completely transform the ecosystems that feed us and provide us with other critical benefits, from flood control to water purification. And yet diseases sometimes serve to maintain the structure and function of the ecosystems on which humans depend.

    Gathering thirteen essays by forty leading experts who convened at the Cary Conference at the Institute of Ecosystem Studies in 2005, this book develops an integrated framework for understanding where these diseases come from, what ecological factors influence their impacts, and how they in turn influence ecosystem dynamics. It marks the first comprehensive and in-depth exploration of the rich and complex linkages between ecology and disease, and provides conceptual underpinnings to understand and ameliorate epidemics. It also sheds light on the roles that diseases play in ecosystems, bringing vital new insights to landscape management issues in particular. While the ecological context is a key piece of the puzzle, effective control and understanding of diseases requires the interaction of professionals in medicine, epidemiology, veterinary medicine, forestry, agriculture, and ecology. The essential resource on the subject,Infectious Disease Ecologyseeks to bridge these fields with an ecological approach that focuses on systems thinking and complex interactions.

    eISBN: 978-1-4008-3788-5
    Subjects: Biological Sciences, Ecology & Evolutionary Biology

Table of Contents

  1. Front Matter
    (pp. i-iv)
  2. Table of Contents
    (pp. v-viii)
    (pp. ix-x)
    Richard S. Ostfeld, Felicia Keesing and Valerie T. Eviner
    (pp. xi-xiv)
    (pp. 1-6)
    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...

  6. PART I Effects of Ecosystems on Disease

    • Introduction
      (pp. 9-11)
      Felicia Keesing

      For many, many years, people have recognized connections between the environment and outbreaks of infectious disease. For example, in the fourth century B.C., Hippocrates developed a “miasmatic” theory that linked malaria transmission to the environment, a link that was strengthened in the 1700s by Giovanni Lancisi, physician to the pope, who recognized that malaria transmission decreased after drainage of wetlands. Lancisi even postulated that mosquitoes might be involved in transmission (Cook and Webb 2000). Two centuries later, in the early 1900s, another environmental connection was proposed for malaria by an Italian public health worker, who suggested that the presence of...

    • CHAPTER ONE Effects of Host Diversity on Disease Dynamics
      (pp. 12-29)
      Michael Begon

      This chapter review insights that have been gained from studies that explicitly acknowledge the contribution of multiple hosts to the dynamics of pathogens. I start from a simple, deterministic viewpoint, distinguishing the contrasting possible effects that a multiplicity of hosts can have on pathogen dynamics, either favoring pathogen persistence or high pathogen abundance (amplification) or reducing these (including especially the dilution effect). A review of the limited available data suggests that although the theoretical possibility of pathogen amplification by multiple hosts is clear, it is not inevitable, in part because transmission between species is rarer than has sometimes been...

    • CHAPTER TWO The Role of Vector Diversity in Disease Dynamics
      (pp. 30-47)
      Alison G. Power and Alexander S. Flecker

      Although many important diseasesof humans, animals, and plants are transmitted by vectors, we know little about the role of vector diversity in disease dynamics. In this chapter we explore two ways in which vector diversity may affect the epidemiology of insect-transmitted plant viruses: through effects on pathogen host range and through effects on transmission rates. Our analysis of a large database of plant viruses indicated that most viruses have a low diversity of vectors and a large diversity of hosts. Nearly 60% percent of vector-transmitted plant viruses have a single known vector species, whereas less than 10% have a single...

    • CHAPTER THREE Understanding Host-Multipathogen Systems: Modeling the Interaction between Ecology and Immunology
      (pp. 48-70)
      Pejman Rohani, Helen J. Wearing, Daniel A. Vasco and Yunxin Huang

      We present a new mathematical framework for exploring the ecological and immunological interactions between multiple infectious diseases. The mechanism underlying the ecological interaction is the modulation of susceptible numbers for one pathogen as a result of isolation or mortality following infection with a competitor. Immunological interactions are assumed to result from immunosuppression or crossimmunity to co-circulating pathogens, both during and after infection. This model is briefly examined to explore the consequences of these factors for the coexistence of multiple infectious diseases. We show that strong competition among pathogens reduces the region of coexistence, while substantial immunosuppression acts to facilitate pathogen...

    • CHAPTER FOUR Influence of Eutrophication on Disease in Aquatic Ecosystems: Patterns, Processes, and Predictions
      (pp. 71-99)
      Pieter T. J. Johnson and Stephen R. Carpenter

      Habitat alteration and disease emergence are among the most pressing environmental concerns facing society. Aquatic ecosystems present a nexus of these issues. In this review, we explore interactions between a particularly widespread form of anthropogenic change, aquatic eutrophication, and the incidence of disease. Our goal was to examine broad-scale patterns in the types of parasites and pathogens favored under eutrophic conditions and how these patterns vary with environment, degree of eutrophication, and type of disease. We considered the consequences of eutrophication on macroparasitic, microparasitic, and noninfectious diseases of humans and wildlife in freshwater and marine ecosystems. We found that eutrophication...

    • CHAPTER FIVE Landscape Structure, Disturbance, and Disease Dynamics
      (pp. 100-122)
      Hamish McCallum

      Landscape structure influences population density and movement patterns of hosts, vectors, and transmission stages. It is therefore selfevident that landscape will influence the dynamics of infectious diseases. Most classic models of infectious disease dynamics do not, however, explicitly include any spatial structure. Its inclusion has major implications for understanding both invasibility and persistence, because in a spatial context, an infected host is more likely to be near another infected host than is the case in a homogeneously mixing system. Understanding landscape is critical in predicting the quantitative spread of infectious disease, because landscape features can be either barriers or conduits...

  7. PART II Effects of Disease on Ecosystems

    • Introduction
      (pp. 125-128)
      Valerie T. Eviner

      While many studies demonstrate that pathogens can have dramatic impacts on their hosts, substantially fewer studies have explored the ecological consequences of these pathogen-induced changes in hosts. Pathogen effects on host behavior, reproduction, and mortality can influence community interactions such as competition, facilitation, predation, and invasion. These pathogen-induced changes in host individuals and communities can have strong impacts on ecosystem processes (e.g., productivity, nutrient cycling) and landscape structure and function (e.g., disturbance regimes, land use, land-atmosphere interactions). While we know that pathogens have thepotentialto shape communities, ecosystems, and landscapes, we still have poor ability to predict the magnitude...

    • CHAPTER SIX Effects of Disease on Keystone Species, Dominant Species, and Their Communities
      (pp. 129-144)
      Sharon K. Collinge, Chris Ray and Jack F Cully Jr

      Keystone species disproportionately affect the abundance and distribution of other species and, because of their central functional role, may significantly influence the dynamics of infectious diseases in the communities in which they occur. For example, changes in the abundance of keystone species due to disease may cause major shifts in community composition and ecosystem function, thereby providing dynamic feedback to disease transmission processes. We highlight specific examples of the effects of disease on keystone and dominant species, using as examples sea otters in coastal California, chestnut trees in the eastern United States, and prairie dogs in western grasslands. Sea otters...

    • CHAPTER SEVEN Red Queen Communities
      (pp. 145-178)
      Keith Clay, Kurt Reinhart, Jennifer Rudgers, Tammy Tintjer, Jennifer Koslow and S. Luke Flory

      We extend the Red Queen hypothesis, a mechanism proposed to maintain genetic diversity at the population level, to explain diversity at the community level. The Red Queen hypothesis assumes that pathogens become specialized on common host genotypes and reduce their fitness, thereby favoring genetic mechanisms generating rare genotypes. Here we develop the idea that pathogens favor diversity in communities by an analogous mechanism of frequency-dependent selection against common species. Empirical evidence from a variety of studies suggests that hostspecific pathogens are more likely to attack and reduce population sizes of common species relative to rare species. Pathogens could therefore counteract...

    • CHAPTER EIGHT Invasion Biology and Parasitic Infections
      (pp. 179-204)
      Sarah E. Perkins, Sonia Altizer, Ottar Bjornstad, Jeremy J. Burdon, Keith Clay, Lorena Gómez-Aparicio, Jonathan M. Jeschke, Pieter T. J. Johnson, Kevin D. Lafferty, Carolyn M. Malmstrom, Patrick Martin, Alison Power, David L. Strayer, Peter H. Thrall and Maria Uriarte

      Parasitic infections can strongly affect invasion success and the impact of invasive species on native biota. A key mechanism facilitating invasion is escape from regulation by natural enemies—the enemy release hypothesis. The level and duration of release depend on the types of parasites lost and gained, with highly regulating acute infections most likely to be lost and, over time, pathogenic RNA viruses likely to be gained. The rate at which hosts accumulate parasites depends on multiple factors, including the biotic resistance of the community and the ecosystem changes induced by the invasive species themselves. We discuss several examples of...

    • CHAPTER NINE Effects of Disease on Community Interactions and Food Web Structure
      (pp. 205-222)
      Kevin D. Lafferty

      Infectious diseases can be powerful forces in natural populations. When diseases affect influential species, the consequences of disease can ramify through communities. For instance, parasites can reverse the outcome of competition and, therefore, alter biodiversity. They may aid or buffer against biological invasions. Parasites permeate food webs and may change communities by altering predator-prey interactions. In particular, they may alter trophic cascades. Infectious human diseases probably limited our influence on the environment in the past. Humans’ continued escape from disease through history has contributed to our having the largest influence over natural communities of any species.

      This chapter considers how...

    • CHAPTER TEN Is Infectious Disease Just Another Type of Predator-Prey Interaction?
      (pp. 223-241)
      Spencer R. Hall, Kevin D. Lafferty, James H. Brown, Carla E. Cáceres, Jonathan M. Chase, Andrew P. Dobson, Robert D. Holt, Clive G. Jones, Sarah E. Randolph and Pejman Rohani

      Which factors fundamentally separate infectious disease from other types of predator-prey interactions studied by community ecologists? Could parasitism and predation be combined into a unifying model? After all, parasites and predators both convert energy and nutrients contained in their resources (hosts or prey, respectively) into new biomass and reproductive work. If these focal consumers perform similar roles, disease ecologists and community ecologists may essentially study the same problems. Therefore, they should use the same conceptual toolkits. Given this important potential for more intellectual crossfertilization, we contemplate these questions by way of two arguments. First, we consider the case that parasitism...

    • CHAPTER ELEVEN Microbial Disease in the Sea: Effects of Viruses on Carbon and Nutrient Cycling
      (pp. 242-259)
      Mathias Middelboe

      Viruses are dynamic and integrated components of both aquatic and terrestrial ecosystems, where they are usually present in abundances of 10⁶–10⁸ viruses per milliliter of water or cm³ of sediment or soil. Most of these viruses are infectious to bacteria, and they constitute a significant mortality factor for prokaryotes in all ecosystems. In the marine environment, 5%–30% of heterotrophic bacteria and cyanobacteria are infected by viruses, and approximately 5%–40% of the daily bacterial and cyanobacterial production is lost as dissolved organic matter due to viral lysis. Also, eukaryotic protists are signifi cantly influenced by viral infections, and...

    • CHAPTER TWELVE Effects of Pathogens on Terrestrial Ecosystem Function
      (pp. 260-283)
      Valerie T. Eviner and Gene E. Likens

      Many studies have demonstrated that pathogens can have strong effects on the performance of individual organisms, population dynamics, and community interactions. A more limited set of studies suggests that pathogens can alter a wide range of ecosystem functions in terrestrial systems; however, we are lacking a framework to predict the type and magnitude of ecosystem effects that a given pathogen will have. In this chapter, we present a number of general principles that determine how pathogens influence ecosystems over time, based on the welldeveloped fields of disturbance ecology and the ecosystem effects of species composition. Our focus is not only...

    • CHAPTER THIRTEEN Disease Effects on Landscape and Regional Systems: A Resilience Framework
      (pp. 284-303)
      F. Stuart Chapin III, Valerie T. Eviner, Lee M. Talbot, Bruce A. Wilcox, Dawn R. Magness, Carol A. Brewer and Daniel S. Keebler

      In this chapter we present and evaluate a conceptual framework intended to improve predictability of the role of disease in landscape processes of socioecological systems. On a local scale, disease tends to increase the interactions among patches on a landscape, particularly through changes in the frequency and severity of disturbances and increases in the vulnerability of ecosystems to fundamental changes in state in response to such disturbances. In addition, human activities that alter landscape structure or connectivity often increase the likelihood of disease epidemics or landscape sensitivity to disease. In contrast, on global and regional scales, disease tends to reduce...

    • CHAPTER FOURTEEN Research Frontiers in Ecological Systems: Evaluating the Impacts of Infectious Disease on Ecosystems
      (pp. 304-318)
      Sharon L. Deem, Vanessa O. Ezenwa, Jessica R. Ward and Bruce A. Wilcox

      Among biologists, the awareness of infectious diseases and their population-, community-, and ecosystem-level impacts has increased dramatically over the past decade. This growth in interest seems to have paralleled an unprecedented global rise in the appearance of new pathogens, the spread of old pathogens, and changes in the pathology of many infectious agents in both humans and wildlife. However, the paucity of historical data makes it difficult to assess whether these current patterns represent a new or unique threat to ecosystem health. To evaluate the level of threat infectious diseases may pose to ecosystems, it is important to examine if,...

  8. PART III Management and Applications

    • Introduction
      (pp. 321-323)
      Richard S. Ostfeld

      The notion of preventive medicine is intuitively appealing. If disease can be prevented before the onset of symptoms, then needless suffering will be avoided, along with associated costs, economic and otherwise. For infectious diseases of humans, vaccinations are a hallmark of preventive medicine, having prevented countless cases of disease. For noninfectious diseases as well, the public health community has had many successes in identifying, for example, dietary, genetic, or lifestyle-related causes of increased disease risk and prescribing preventive measures. In a sense, preventive medicine is the acid test of epidemiology and public health. Only if the causes of variable patterns...

    • CHAPTER FIFTEEN The Community Context of Disease Emergence: Could Changes in Predation Be a Key Driver?
      (pp. 324-346)
      Robert D. Holt

      All host-pathogen interactions play out against a background of other ecological drivers and the web of interactions in local communities. Parasites can infect multiple host species, and most host species are subject to infection by multiple parasites. Predators can affect hostpathogen interactions by acting as mortality factors or by facilitating disease transmission. Environmental change alters this background of species interactions and thus can indirectly modify host-pathogen dynamics in a variety of directions. Each of the many dimensions of environmental change—extirpation of endangered species, introduction of exotics, harvesting, habitat alteration and fragmentation, the addition of toxicants and pollutants, eutrophication, and...

    • CHAPTER SIXTEEN The Emergence of Wildlife Disease and the Application of Ecology
      (pp. 347-367)
      Peter J. Hudson, Sarah E. Perkins and Isabella M. Cattadori

      Since most emerging diseases are zoonotic infections derived from wildlife, they can be considered invasive species that exploit a new habitat. In this paper we consider emerging diseases as interspecific transmission events, but the fitness of the invading parasite is determined by the success of subsequent dispersal (transmission) to new resource-rich patches (susceptible hosts) and sustaining the chain of transmission. Successful invasion does not depend simply on invading a closely related host species but on the number of times invasion is attempted and the size of the individual dose. Successful invasion also depends on the presence of competitors and release...

    • CHAPTER SEVENTEEN Applied Biodiversity Science: Managing Emerging Diseases in Agriculture and Linked Natural Systems Using Ecological Principles
      (pp. 368-386)
      K. A. Garrett and C. M. Cox

      Pathogen reproduction tends to be host frequency dependent, so that disease may be more problematic when particular crop species or genotypes are very common. Nonetheless, production agriculture is dominated by extensive monocultures. This situation is partly an artifact of agricultural policy and decision making, but it also reflects the real challenges of understanding and manipulating the ecological genomics of a single crop genotype, not to mention multiple species and genotypes. There are trade-offs in investing agricultural research in many versus only a few agricultural species. Agricultural diseases may emerge or reemerge for a number of reasons, including new pathogen introductions,...

    • CHAPTER EIGHTEEN The Ecology of an Infectious Coral Disease in the Florida Keys: From Pathogens to Politics
      (pp. 387-403)
      James W. Porter, Erin K. Lipp, Kathryn P. Sutherland and Erich Mueller

      Coral reefs are in severe decline. Between 1996 and 2000, 38% loss of living coral cover was recorded in the Florida Keys. By far the greatest loss, in terms of both absolute abundance and percent loss, occurred in the elkhorn coral,Acropora palmata. Once the most common coral in the Caribbean, this species had lost more than 90% of its surface area in the Florida Keys. All elkhorn populations observed to decline in the Florida Keys exhibited signs of white pox disease prior to demise. The pathogen that causes white pox isSerratia marcescens, a common fecal enteric bacterium found...

    • CHAPTER NINETEEN Infection and Ecology: Calomys callosus, Machupo Virus, and Acute Hemorrhagic Fever
      (pp. 404-422)
      Karl M. Johnson

      Attempts to explain the origin and transmission of pathogens and how they variously cause disease certainly require knowledge of pathogen biology and biomedical science. But time and again, ecological methods have proved critical for understanding the interactions that can lead to prevention or control of infection, as well as for appreciating evolutionary history relevant to the origins and dissemination of given pathogens.

      This chapter is a personal account of such discovery and how my team and I came to partially understand the underlying ecology of a particularly deadly zoonotic virus that causes severe human disease.

      Beginning in 1959, residents of...

    • CHAPTER TWENTY Resolved: Emerging Infections of Humans Can Be Controlled by Ecological Interventions
      (pp. 423-440)
      C. J. Peters

      It has become very apparent over the past decade that new and emerging viruses will plague us for the foreseeable future. The causes were addressed in detail by a recent Institute of Medicine report, and the conclusions were that underlying factors would only worsen in an accelerated fashion and that interactions among these factors would exacerbate the situation. Equally alarming is the fact that new vaccines, anti-infectives, and mea sures directed against vectors and reservoirs are not being developed by commercial or public sector researchers. This chapter analyzes ten recent serious emerging viral infections and concludes that ecological factors drive...

    • CHAPTER TWENTY-ONE From Ecological Theory and Knowledge to Application
      (pp. 441-447)
      James E. Childs

      This chapter considers means to increase communication and understanding between practitioners of infectious disease ecology (IDE) and mainstream public and veterinary health practitioners (PVHP). Successful integration of the remarkable achievements and advances in IDE into standard health practice would improve human, animal, and ecosystem health.

      The discussion of IDE focuses on academically based scientists who are developing theoretical constructs of the interaction of pathogen and host populations mediated by disease and immunity (Anderson and May 1991; Nowak and May 2000), scientists who are developing mathematical models or simulations of specific disease processes or epidemiological patterns of disease spread (Coyne et...

    • CHAPTER TWENTY-TWO Educating about Infectious Disease Ecology
      (pp. 448-466)
      Carol A. Brewer, Alan R. Berkowitz, Patricia A. Conrad, James Porter and Margaret Waterman

      Human health depends on healthy ecosystems, and ecosystem health depends on human choices. Because people play key roles in moving diseases around and modifying the environment in ways that determine the prevalence, spread, and severity of diseases, every citizen needs to understand the basic linkages between ecosystems, diseases, and health. In this chapter we address the thinking skills and essential habits of mind needed to understand the ecology of infectious diseases (IDE) and to develop the self-confidence, motivation, and skills to use their understanding in their professional and personal lives. Today, there are few examples of IDE or of effective...

  9. PART IV Concluding Comments:: Frontiers in the Ecology of Infectious Diseases

    • The Ecology of Infectious Diseases: Progress, Challenges, and Frontiers
      (pp. 469-482)
      Richard S. Ostfeld, Felicia Keesing and Valerie T. Eviner

      Recent years have seen explosive growth in research activity devoted to understanding the ecology of pathogens and the diseases they cause. The importance of pathogens and diseases to humans, wild and domesticated animals, and plants has been recognized since antiquity. Only recently, however, has the science of ecology assumed a major role in understanding disease dynamics. Ecologists are beginning to routinely include pathogens as focal study organisms and to incorporate them and their consequences into the communities and ecosystems under study. The incorporation of ecological perspectives into the forecasting, prevention, and management of human diseases, however, remains rare; it is...

  10. INDEX
    (pp. 483-506)