WILDLIFE HEALTH AND DISEASE: SURVEILLANCE, INVESTIGATION,

AND MANAGEMENT

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

Introduction 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

DISEASEDefinition: 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

Veterinarians/physicians Pathologists

Microbiologists/Parasitologists Epidemiologists

Wildlife biologists

• Organ system • Disease abnormality

• Etiological agent • Mode of transmission

• Host species involved

Cardiology Dermatology Neurology Ophthalmology

Ulcerative colitis Spongiform

encephalopathy Hemorrhagic

enteritis

Bacterial Viral Mycotic Parasitic Toxic

Direct Indirect

The “grouse disease”

Diseases of deer

Diseases of waterfowl

Interactive Relationships

Epidemiological Perspective

Agent

Host Environment

Ecological Perspective

Parasite

Host Habitat

Effect of Environmental/Habitat Factors

Relative balance

Parasite/

AgentHost

Favors host

Parasite/

Agent Host

Favors parasite/Agent

Parasite/

Agent

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

Agent

Host Environment

Agent

Host Environment = habitat of both host and parasite

Resources►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

►Field observations►Environment or Habitat►Magnitude and Onset►Temporal Distribution►Geographic Distribution►Species, Age, and Sex►Clinical Signs

Resources and Methods for Disease Investigation

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; a ubiquitous 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 Olaus J. Murie 1930

Upper: young elk in last stages of diseaseLower: elk calf in last stages of disease

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 Olaus J. Murie 1930

Upper: characteristic wad of foodLower: dying elk calf

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 intervention

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)

SUMMARY► 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

SUMMARY

► 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!