Wildlife health and disease surveillance investigation and management
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WILDLIFE HEALTH AND DISEASE: SURVEILLANCE, INVESTIGATION, AND MANAGEMENT. Markus J. Peterson 1 and Pamela J. Ferro 2 1 Department of Wildlife and Fisheries Sciences, 2 Department of Veterinary Pathobiology, Texas A&M University College Station, TX 77843, USA. Introduction.

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Markus J. Peterson1 and Pamela J. Ferro2

1Department of Wildlife and Fisheries Sciences, 2Department of Veterinary Pathobiology, Texas A&M University College Station, TX 77843, USA


  • Wildlife health and disease important in wildlife conservation.

    • Species at risk of extinction

    • Human health

  • 60% of 335 emerging infectious diseases worldwide since 1940 were zoonoses, 72% originated in wildlife (Jones et al 2008).

  • Proportion of emerging infectious diseases originating in wildlife has increased since 1940 (Jones et al 2008).

Historical Perspective

Wildlife health and disease—often integral to early wildlife studies (e.g., Com. Inq. Grouse Dis. 1911, Stoddard 1931, Leopold 1933)

By 1950s, leading wildlife scientists typically perceived wildlife diseases to be simply extensions of inadequate habitat (e.g., Trippensee 1948, Lack 1954, Taylor 1956)

By 21st century, problems associated with chronic wasting disease, bovine tuberculosis, West Nile virus, rabies, etc., in wild hosts reemphasized the ecological and management importance of wildlife diseases


  • Definition: Interruption, cessation, or disorder of body functions, systems or organs

    • In addition to macro-and microparasites, includes:

      • Toxic

      • Genetic

      • Metabolic

      • Behavioral

      • Neoplastic

      • Nutritional diseases

Various Taxonomies of Disease Classification

Interactive Relationships

Epidemiological Perspective

Ecological Perspective







Effect of Environmental/Habitat Factors

Favors parasite/Agent

Relative balance

Favors host







Change in View of Disease on Population Dynamics

  • Traditionally, epidemiologists did not address the influence of infectious agents on human population dynamics

    • Pioneering work by Anderson and May (1978,1979) demonstrated that if predatory mammals and birds can influence prey population dynamics, it is just as reasonable to assume macro- and microparasites (ecologically predators as well) have the same potential

Change in Epidemiological Perspective





Environment = habitat of both host and parasite



  • Many resources available

    • Web based

    • Manuals

  • Common formats:

    • By host species or related groups of species

    • A single disease in array of host species

    • By region

    • By class of etiological agent

Detailed Reviews of Wildlife Diseases

  • Summarizes literature

  • Cautions:

    • Out of date

      • For most diseases, doesn’t matter much

      • In areas with considerable on-going research, need to supplement with current literature

    • Some sources contain unpublished data; thus, not simply a review of what was known

Sources for Wildlife Disease Expertise

  • Wildlife health centers (U.S. and Canada)

    • National

    • Regional

    • State/provincial laboratories

  • Some offer training

  • Source of expertise

Resources and Methods for Disease Investigation

  • Field observations

  • Environment or Habitat

  • Magnitude and Onset

  • Temporal Distribution

  • Geographic Distribution

  • Species, Age, and Sex

  • Clinical Signs

Laboratory Procedures

  • Pathology

    • Necropsy

    • Histopathology

  • Microbiology

    • Bacteriology

    • Mycology

    • Virology

    • Parasitology

    • Serology

  • Clinical Chemistry and Hematology

  • Toxicology

Specimen Collection and Handling

  • Proper training essential

  • Send whole carcass to laboratory if possible

  • If not, use safe procedures

  • Ship samples according to national regulations

Managing Wildlife Diseases

  • Classes of management objectives:

    • Preventing infectious agent from becoming established (preferred)

    • Controlling an existing disease

    • Eradicating an existing disease (most difficult)

  • Management manipulation can target hosts, parasite/agent, and/or habitat/environment

Managing Disease

  • Requires various approaches

    • Must assess the situation

    • Adjust accordingly

Case Study #1: Necrotic Stomatitis in Elk

  • Once described as “by far the most important elk disease” (Murie 1951)

  • Today, few have heard of the disease, or find it an interesting historical note

  • Causative agent: Fusobacterium necrophorum; aubiquitous microorganism that is part of normal intestinal and fecal flora

Case Study #1: Necrotic Stomatitis in Elk (cont.)

  • Problem:

    • When elk densities approach K-carrying capacity for winter—forced to browse on coarse twigs and branches

    • Generates abrasions, punctures, etc.

    • Open wound for entry of bacterium

  • Result: infection, illness, sometimes death

Upper: young elk in last stages of disease

Lower: elk calf in last stages of disease

Olaus J. Murie 1930

Case Study #1: Necrotic Stomatitis in Elk (cont.)

  • Resolution:

    • Since part of normal gut flora, cannot eliminate

    • Management focus:

      • Winter habitat

      • Elk density

    • Management of winter range

      • Initially, not effective because hay contained sharp foxtail barley, cheatgrass seeds, and awns (causing wounds)

      • Only high quality hay

    • Reduction in Elk densities

Upper: characteristic wad of food

Lower: dying elk calf

Olaus J. Murie 1930

Case Study #2: Rabies in Wild Carnivores

  • Different from necrotic stomatitis because:

    • Causative agent not commensal

    • Rhabdovirus

      • Essentially disease of mammals, primarily

        carnivores and bats

      • Most commonly, transmitted through bite

      • Incubation varies from less than a week to

        several years, depends on several factors

    • Long incubation period

      • Allows for normal movement of infected animals

      • Can shed virus for several days before becoming clinically ill

Case Study #2: Rabies in Wild Carnivores (cont.)

  • Typically occurs at low rates in populations of wild canids

  • When density of susceptible hosts exceeds threshold required for rapid transmission  epidemic

  • Becomes problem for humans during epidemics because more likely to spillover

    • Increasing human encroachment

Case Study #2: Rabies in Wild Carnivores (cont.)

  • Management:

    • Focuses on reducing density of susceptible hosts

      • Lethal methods

        • Problem: public opposition

        • Implementation proved ineffective (Rupprecht et al. 2001)

      • Vaccination

        • Immunization of pets (since closest contact to humans)

        • Key wildlife species (e.g. coyotes, foxes)

          • Oral vaccination through bait

          • Challenging in some species: i.e., raccoons and skunks

Case Study #3: Brucellosis in Elk

  • Bovine brucellosis disease of reproductive tract in cattle

  • Causative agent: Bacterium Brucella abortus

  • Cattle, bison, and African buffalo can sustain infection without human intervention

Case Study #3: Brucellosis in Elk (cont.)

  • Causes abortion during last half of gestation or birth of non-viable calves in both bison and elk

  • Mode of transmission:

    • Licking infected material (e.g., fetuses, calves, placentas, or vaginal discharge)

    • Consuming contaminated feed

    • Consuming contaminated placentas

    • Licking genitalia of infected females soon after abortion or birth

  • Wide array of susceptible hosts

    • Wild ungulates, carnivores, rodents, lagomorphs, humans, and other mammals; cattle and other domestic livestock

Case Study #3: Brucellosis in Elk (cont.)

  • Bovine brucellosis formerly occurred worldwide in cattle, eradication programs targeting livestock reduced distribution

    • USDA coordinated eradication program

    • As of 2000, 48 US states classified as brucellosis free

  • Thus, reservoirs such as bison and elk in Greater Yellowstone Area, considered threat to this program

  • Brucellosis in elk, problem of wintering grounds

    • Increased elk densities during period when females abort or give birth to infected calves due concentrated elk densities on winter feed grounds

    • Feeding grounds are shared space:

      elk, bison—can maintain B. abortus

      in the population without human


Case Study #3: Brucellosis in Elk (cont.)

  • Solution:

    • Reduce density of susceptible hosts

      • Vaccination

        • Vaccine not particularly efficacious in elk

        • Difficult to deliver vaccine

      • Decrease number of elk in population

        • Decrease to capacity winter habitat can support

        • Discontinue winter feeding (feeding grounds)

  • Problems with solution:

    • Primarily sociopolitical

      • Public pressure to continue winter feeding

      • Many people enjoy high elk densities provided by winter feeding (hunters, wildlife enthusiasts, tourists, guides, chambers of commerce)


  • Case studies illustrate different problems and strategies for wildlife disease management

    • Case 1: Problem for wildlife health; habitat/environment changes is key to management

    • Case 2: Problem primarily for human health; reducing density of susceptive hosts is key to management

    • Case 3: Problem primarily for livestock health; negotiating sociopolitical challenges is key to management

  • Each presented specific challenges to overcome based on situation

    • Agent, host, habitat/environment, public perception


  • Wildlife health and disease becoming increasingly important to wildlife conservation

    • Threat to human and livestock health as well as biodiversity conservation

  • Wildlife biologists bridge disciplines

    • Provide holistic, ecological approach

    • Must be able to adapt to situation and circumstances

  • Most importantly: Use available resources and OBTAIN PROPER training!

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