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Tufts OpenCourseware
Author: Mark Pokras, D.V.M.

OCW Zoological Medicine 2008
Conservation Medicine in Practice (2009)
M. Pokras, DVM
Cummings School of Veterinary Medicine at Tufts University

1. Conservation Medicine in Practice – why veterinary medicine belongs

1.1. Focus on Ecosystem Health

1.1.1. How do we define health?

  • Absence of disease

  • Having the capability to achieve one's fullest potential

Some three decades before the Rio Summit ('92), human health was defined by the World Health Organization as, "...a complete state of physical, mental and social well-being, and not merely the absence of disease or infirmity." Therefore, the metaphorical concept of ecosystem health must incorporate the dynamic interrelations among natural systems, human activity, and social organization, not merely focus on ecosystem deterioration or human health risks, manifested in the resurgence and spread of old epidemics and the emergence of new ones.

1.1.2. Defining Ecosystem Health

More than half a century ago, Aldo Leopold suggested the notion of "land sickness," referring to the breakdown of regional terrestrial (and aquatic) ecosystems to whole landscapes by human activities. He drew attention to specific signs (e.g., erosion, loss of soil fertility, hydrological abnormalities, occasional irruption of certain species, mysterious local extinction of others, and qualitative deterioration in farm and forest products) by which this condition might be recognized.

Healthy Ecosystems are ..."Sustainable and stable state of ecological systems capable of maintaining organization, autonomy and resistance to stress" - Costanza et al. 1992.

David Rapport : ('85) - Identified that stressed ecosystems are characterized by reduced biodiversity and altered primary and secondary productivity but also by increased disease prevalence, reduced efficiency of nutrient cycling, increased dominance of exotic species, and increased dominance by smaller, shorter-lived opportunistic species. Ecosystem Distress Syndrome (EDS) – (Rapport, 1999)

  • "A high prevalence of diseases is one of the key indicators of the pathology of ecosystems, and a sick ecological system increases the health risks of its components."
    "…a collection of symptoms signaling that an ecosystem is being pushed to its limits. EDS Presages the transformation of an ecosystems into something different, usually something less productive, something less useful to humans."

  • Biological impoverishment: loss of biodiversity & disruption of ecological processes

  • Global toxification: contaminants, hazardous waste and endocrine disruptors

  • Global climate change/ ozone depletion

  • Human ecological footprint expands as a result of population growth

  • Overloaded air -- clarity, ozone, chemicals, effects on plant growth & wildlife health, etc.

  • Overloaded water -- loss of wetlands, decreased water quality, sediments, contaminants, decr. health of organisms

  • Overloaded soils -- loss of biodiversity & productivity of communities, loss of functions of soil (absorption, transformation & recycling), erosion (affects water) -- septic systems, storm drains, pavement effects

  • Loss of biodiversity -- shift in dominance of biota from the larger, longer-lived life forms that are specialists in their food requirements to smaller, shorter-lived forms that are generalists

  • Loss of biological productivity

1.1.3. Ecosystem Fragmentation – edge effect

  • Amphibians

  • Turtles

1.1.4. Stressors

  • Marine iguana

  • Spotted owl

1.1.5. Diagnostic tools for assessing health

  • Multi-disciplinary tools

  • Rapid assessment

  • Ecological epidemiology

  • Remote sensing

  • Integrated assessment

  • Surveillance studies -- quality of air, water, & soils, density of grazing animals, pollutants, productivity & diversity of biological systems, etc.

  • Monitoring protocols

1.1.6. Defining solutions and treatments

  • The Precautionary Principle

  • Invasive activity

  • Management

  • Conservation

  • Public policy

  • Evaluation of remediation strategies

1.2. Emerging disease & developing zoonoses

"The wild beasts of this century and the next are microbial, not carnivorous" - Joel Cohen
  • Ecological change

  • Human demographic & behavior shifts

  • International travel and commerce

  • Technology and industry

  • Microbial adaptation and change

  • Breakdown in public health measures

  • Cumulative & Synergistic - effects of multiple stressors

1.2.1. Consequences of Emerging Infectious Diseases

  • EIDs causing mass mortality events

    • Population declines

    • Local extinctions

    • Global extinctions

  • EIDs causing subtle population loses

    • death, decreased reproduction, deformities, etc.

1.2.2. Basic Concepts in Disease Emergence

  • Mary Wilson, 1995

    • Emergence of EIDs is complex

    • Infectious diseases are dynamic

    • Most new infections not caused by genuinely new pathogens

    • The concept of the microbe as the cause of the disease is incomplete and inadequate

    • Human factors are the most potent factors driving disease emergence

    • The current global situation favors disease emergence

  • Daszak et al. 2000

    • Spill-over

      • from domestic animals

      • from humans

      • from imported wildlife

    • Pathogen pollution - translocation of host, vector and/or pathogens

      • for conservation

      • for hunting

      • for agriculture & food

      • for pet trade

      • for fashion, whim, ethos

      • by accident

    • Passive emergence - no "overt" human involvement, e.g. Climate change

      • Warming

      • Sea level

      • Ozone thinning & UV

      • Climatic instability

Origin of Hantavirus Pulmonary Syndrome in USA

Six year drought
Reduction of predator populations
Heavy rains > > heavy seed crop
Depleted predator and increased rodent populations
Elimination of virus in feces and urine
Human exposure by inhalation of aerosols
Epidemic of HPS

1.3. Climate change

  • Shifts of species & food sources

1.4. Medical geology

  • Hg pollution in fish eating birds & humans

1.5. Toxics & interactions with disease

1.6. Animal movements

  • Exotic species, including pets, invertebrates & plants

  • Direct ecologic effects

  • Vectors/intermediate hosts

  • Examples: plague, rabies, monkeypox

1.7. Agricultural impacts

  • Antibiotics

  • Nutrients & runoff

  • Toxics

  • Disease

  • Fragmentation

  • Some positives:

    • open space preservation

    • polyculture

    • organic agriculture

2. What are the roles for veterinarians?

  • Eyes & ears - reportable, networking, integrative health issues

  • Be educators in your practice & community

  • Be part of solution, NOT problem

  • Important research & policy opportunities

  • Veterinary means ALL animals... but can't ignore plants

We need....

  • Surveillance & epidemiology

  • Research

  • Greening Veterinary Medicine

  • Public Education

  • Changes in human attitudes

    • towards wildlife & exotic species

    • towards human population

    • towards achieving a balance

3. References and Resources

3.1. Organizations and websites

Aquatic Ecosystem Health & Management Society P.O. Box 85388, Brant Plaza Postal Outlet Burlington, Ontario CANADA L7R 4K5.

Millennium Ecosystem Assessment: strengthening capacity to manage ecosystems sustainably for human well-being.

ProMED-mail web site at

Emerging Infectious Disease journal (CDC)

WHO Rabies Network

AHEAD Emerging Animal Disease (Fed. of Amer. Sci.)

USGS--National Wildlife Health Center

3.2. Books

Aguirre, Alonso, et al. (ed.) Conservation Medicine: Ecological Health in Practice . Oxford University Press, 2002.

Calder WA III. Size, function and life history . Cambridge,MA:Harvard Univ. Press.1984.

Carson, R., 1962. Silent spring . Houghton Mifflin Pub. Boston, MA

Colburn, T. et al. 1996. Our stolen future . Dutton Pub.NY

Costanza, R (ed). 1992. Ecosystem Health: New Goals for Environmental Management . Island Press, Washington, DC.

DeSalle, R. (ed). 1999. Epidemic! The world of infectious disease . The New Press, NY.

Disease Emergence and Resurgence : The Wildlife-Human Connection. U.S. Geological Survery, National Wildlife Health Center.

Furness, RW and JJD Greenwood. 1993. Birds as monitors of environmental change . Chapman & Hall. London.

Garrett, L. 1994. The coming plagues . Farrar, Strauss and Giroux. New York.

Graham, F. 1970. Since silent spring . Houghton Mifflin Pub. Boston, MA

Leopold, Aldo. A Sand county almanac . Ballantine Books, reissue 1986.

McCormick, JB and S Fisher-Hoch. 1996. Level 4: Virus hunters of the CDC . Turner Pub. Atlanta

Moeller, DW. 1992. Environmental Health . Harvard Univ. Press.

Peters,R.H. The ecological implications of body size . New York: Cambridge Univ. Press. 1983.

Rapport, D, et al. 1998. Ecosystem Health: Principles and Practice . Blackwell Science.

Ryan, F. 1997. Virus X: tracking the new killer plagues . Little, Brown & Co.

GeoYearbook: an overview of our changing environment 2004/5. United National Environment Programme.

Wilson EO.1992. The diversity of life . Press, Cambridge, MA.

3.3. Journal articles

The domestic animal/wildlife interface: issues for disease control, conservation, sustainable food production, and emerging diseases . Annals of the New York Academy of Sciences . 2002. Volume 969.

Burkholder, J M. 1999. The Lurking perils of Pfiesteria. Scientific American , Aug. pp. 42-49.

Callicot, JB et al. 1999. Current normative concepts in conservation. Cons. Biol . 13(1): 22-35.

Daszak, P, Cunningham, AA and AD Hyatt. 2000. Emerging infectious diseases of wildlife. Science , 287(5452):443-449.

Dobson AP, May RM.1982. Disease and conservation. In: Soule, M (ed) Conservation biology . Sinauer Assoc., MA pp: 345-365.

Epstein, PA. 1999. Climate and health. Science , Vol. 285, 16 July, pp. 347 -348.

Epstein, PA. 1995. Emerging disease and ecosystem instabilities: new threats to public health . Am J Pub Health 85 (2):168-172.

Harvell, CD et al.1999. Emerging marine disease: climate links and anthropogenic factors. Science , 285 (5433):1505

Koch M.1996. Wildlife, people and development: veterinary contributions to wildlife health and resource management in Africa. Trop. Anim. Hlth. Prod ., 28: 68-80.

Kruess A, Tscharntke T.1994. Habitat fragmentation, species loss and biological control. Science . 264 (5165):1581-1584.

Landres, PB, Verner, J and JW Thomas. 1988. Ecological uses of vertebrate indicator species: a critique. Cons. Biol . 2(4):316-328.

LeBlanc, Gerald. Are Environmental Sentinels Signaling? Environmental Health Perspectives , volume 103, number 10, October 1995.

Nisbet. ICT. 1994. Effects of pollution on marine birds. In: Nettleship, DN et al (eds).

Seabirds on islands. BirdLife International . Cambridge, England: 8-25

Patz, J. et al. 1996. Global climate change and emerging infectious diseases. JAMA. 275 (3):217-223.

Pimentel, David et al. 1998. Ecology of increasing disease. Bioscience, Oct.

Pokras, MA,Tabor, G, Pearl,M, Sherman, D, and P Epstein. 2000.Conservation medicine: an emerging field. In: Nature and human society: the quest for a sustainable world . National Academy Press. Washington, DC. pp: 551-556.

Rapport, DJ and WG Whitford. 1999. How ecosystems respond to stress. BioSci . 49(3):193-203.

Sherman, DM, Pokras, MA and AW English. 1999. Preparing veterinarians for meaningful participation in wildlife conservation. J Vet Med Educ . 26(1):26-29.

Silva, M and JA Downing.1998. Allometric scaling of minimal mammal densities. Cons. Biol . 8(3):732-743.

Steidinger KA, Burkholder JM, Smith SA.1996.Pfiesteria piscida gen. et sp. nov.: a new toxic dinoflagellate with a complex life cycle and behavior. J. Phycol . 1996; 32(1):157-161.

Thorne, ET, Williams ES.1988. Disease and endangered species: the black-footed ferret as a recent example. Cons.Biol . 2(1):66-74.

Walker, DH. et al. 1996. Emerging bacterial zoonotic and vector-borne diseases: ecological and epidemiological factors. JAMA 275(6): 463-469.

Walters, Mark Jerome. 2003. Six Modern Plagues and How We are Causing Them . Washington, Island Press.