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)
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
► By
DISEASE
 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
Veterinarians/
physicians
Pathologists
Microbiologists/Par
asitologists
Wildlife
biologists
Epidemiologists
•
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
Ecological Perspective
Agent
Host
Parasite
Environment
Host
Habitat
Effect of Environmental/Habitat
Factors
Relative balance
Parasite/
Agent
Favors host
Favors parasite/Agent
Parasite/
Host Agent
Host
Host
Parasite/
Agent
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
Agent
Host
Environment
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
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
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
► Once
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
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
► Many
pressure to continue winter feeding
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!