Ecology of diseasesDr. Bhoj R singh, Principal Scientist (VM)

I/C Epidemiology; Centre for Animal Disease Research and DiagnosisIndian Veterinary Research Institute, Izatnagar-243122, Bareilly, UP, India.

TeleFax +91-581-2302188

Ecology

• Ecology (Greek: οἶκος, "house"; -λογία, "study of”) is the scientific study of interactions among organisms and their environment.

• Interactions which organisms have with each other (biotic) and with their abiotic environment.

• Ecology also deals with the diversity, distribution, amount (biomass), number (popultion) of organisms, as well as competition between them within and among ecosystems. 

Disease ecology• The ecology of infectious disease is an important, growing sub-discipline of ecology

that combines field studies, epidemiology, molecular approaches, and modeling to understand interactions among wildlife hosts, vectors, and pathogens, and to better forecast risk of disease." (Paul Stapp, from EcoHealth 4:121 124� )

• The study of the underlying principles that influence the spatio-temporal patterns of diseases. Incidence, spatial distribution, and timing of diseases reflect the interactions of populations with each other. Diseases may be environmental (i.e., caused by things like toxins, cancers, environmental shortages such as famine), or infectious (i.e., caused by pathogens).

• The interaction of the behaviour and ecology of hosts with the biology of pathogens, as it relates to the impact of diseases on populations. (Sci-Tech Encyclopedia Online)

• The study how hosts and pathogens interact in populations, communities and even entire ecosystems." (Les Real, Emory University)

• Disease ecology is interdisciplinary field that necessarily involves the disciplines of microbiology, ecology, genetics, geography, medicine, mathematics and epidemiology to better understand how climate and environment affects the interaction between hosts and pathogens." (Margie Lee, University of Georgia)

Disease ecology

• Many diseases are result of filing to understand ecology of diseases, disturbing the ecosystem without knowing the consequences viz., Plague, Malaria, AIDS, Ebola, West Nile, SARS, Lyme disease and hundreds more.

• Any emerging disease in the last 30 or 40 years has come about as a result of encroachment into wild lands and changes in demography, says Peter Daszak, a disease ecologist and the president of EcoHealth.

• Sixty percent of emerging infectious diseases that affect humans are zoonotic — they originate in animals. And more than two-thirds of those originate in wildlife.

Objectives• Why do the patterns of disease occur as they do?

Conceptual: what variables are important?• To figure out, the ways in which people alter the landscape — with a new

farm or road, for example — where the next diseases are likely to spill over into humans and how to spot them when they do emerge, before they can spread.

• To study the interaction of the behaviour and ecology of hosts with the biology of pathogens, as it relates to the impact of diseases on populations.

• The environmental impact assessment (EIA)• EIA has three main functions:• • to predict problems,

• to find ways to avoid them, and• to enhance positive effects.

What is the challenge and areas of research in ecology of diseases?

• The challenge is to understand – Ecological and evolutionary aspects of infectious diseases; – Develop an understanding of the interactions among pathogens,

hosts/receptors, and the environment; – To make it possible to prevent changes in the infectivity and virulence

of organisms that threaten plant, animal, and human health at the population level.

Important research areas include:– Examining the effects of environmental changes as selection

agents on pathogen virulence and host resistance; – Exploring the impacts of environmental change on disease

aetiology, vectors, and toxic organisms; – Developing new approaches to surveillance and monitoring; and – Improving theoretical models of host-pathogen ecology."

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How it is different?

• Differs from a traditional medical approach in that it’s not concerned with describing the pathology of individuals

• Differs from epidemiology in that the emphasis �is on general processes of population interactions rather than characterization of specific diseases.

• Populations are systems of organisms interacting with and in the environment, and these interactions result in emergent properties.

• Emergent properties: outcomes of higher-order interactions among components of a system that can’t be anticipated by studying the components in isolation

Example: can the introduction of an efficacious.vaccine actually make a disease situation worse?

• Basic concept of disease ecology is related to the niche.• Niche: those sets of biotic and abiotic conditions in the environment

that define the limit of a species’ ability to survive.• In disease ecology, the dynamics of infectious disease are viewed as �

the overlap in time-space of niches of the component populations.• Spatio-temporal fluctuations in niche overlap affects disease rates

Disease ecology in News• Climate Change and Disease Ecology, Science Daily, August 15, 2007• Employing Ecology to Predict and Manage Infectious Diseases

, Science Daily, May 10, 2005• When Animals Sound a Warning. Yale Medicine, Spring 2006• Grad Specialization Created in Wildlife Disease Ecology. MSU

News Bulletin, October 24, 2002• WA Govt Urged to Invest More in Wildlife Disease Research.

ABC Perth, July 13, 2007• Conference Signals Growth of Disease Ecology Field. Emory Report, June 7, 2004• UGA symposium explores the role of climate and ecology on infectious disease.

UGA Press Release, March 29, 2007• UGA to inaugurate new lecture series on infectious disease ecology. UGA

Press Release, March 21, 2006• Amphibian Declines, Disease Ecology, Biodiversity Are Highlighted at Conference.

NSF Press Release, August 8, 2006

Books

• Infectious Disease Ecology: Effects of Ecosystems on Disease and of Disease on Ecosystems . Eds. Richard S. Ostfeld, Felicia Keesing, Valerie T. Eviner. Princeton University Press, Princeton and Oxford

• The Ecology of Wildlife Diseases. Peter J. Hudson. Oxford University Press, Oxford.