Wildlife Diseases

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• Wildlife Diseases
• An overview of selected examples
• (with tests of your wildlife forensic skills!)
• .

Many diseases can exist as chronic, often
low-level infections (enzootic) or as
rapidly-spreading, erruptive infections
(epizootic)
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Botfly larvae Ugly but not lethal!
Text example Problem Hunter reaction Management
Season Start
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Papilloma/fibroma viruses (warts) Ugly but not
lethal unless disrupt vision etc Usually attacked
by immune system
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Avian Pox (Virus) Vector Mosquito or contact
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Mange caused by mites usually nonlethal,
Sarcoptic mange Can be lethal Outbreaks in wild
canids in N. America May be of concern for small
populations or pops of special concern
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A wildlife forensics quiz
Dead rabbits or rabbits acting lethargic, easily
approached, or having trouble running
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Toxin or Tularemia - bacterial infection
In U.S., rabbits source of infection in 90 of
human cases of tularemia, 70 of which result
from contacts with cottontails. Jackrabbits are
an important source of infection in some areas,
but are a minor factor nationally. Snowshoe hares
comprise less than 1 of the source of human
infection.
Transmission bloodsucking arthropods
  Symptoms Hunters should be very suspicious of
"lazy" rabbits which are easily
killed Treatment/Management See text example
Human Concerns Can be deadly in humans.
Rubber gloves should probably be worn when
dressing rabbits. The meat of these animals
should be thoroughly cooked.
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Dead birds, especially members of the crow/jay
family (corvids)
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Toxin or West Nile Virus (WNV) Encephalitis
(inflammation of the brain) Meningitis
(inflammation of the lining of brain and spinal
cord).  Transmission mosquitos  
Symptoms uncoordinated walking, weakness,
lethargy, tremors, and abnormal head posture.
Although crows and blue jays account for between
50 and 90 percent of reported avian cases, WNV
infection has been identified in over 170 other
avian species across North America.
Treatment/Management monitoring, mosquito
eradication Human Concerns When the level of
virus transmission among birds and mosquitoes
becomes high, horses and humans can be
incidentally infected. Only 1 of humans bitten
actually become infected.
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Emaciated, slobbering, wide-legged stance, poor
coordination
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If Cervid, Chronic Wasting Disease CWD
Agent prion Prion proteins can be passed in
predator feces, decaying matter, etc. Prions
cause conformational change in other proteins.
These are slow to build-up, explaining the time
required for symptoms to develop
First recorded in deer in Colorado, has spread to
many western states and recently to Wisconsin
Attacks central nervous system, leads to
emaciation and eventual death Transmission
unknown Treatment/Management Monitoring of
brain tissue and containment Restricted
transport of live cervids, and import of nervous
tissue Reducing density of deer in infected
areas Human concerns avoid contact with nervous
tissue
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Malnutrition
Symptoms Emaciation, lethargic, unsteady,
reduced fear response
Dont rule out other potential factors.
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Mass waterfowl deaths, waterfowl weak, easily
approached, may act partially paralyzed
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Avian cholera bacteria Transmission spread
by contact between healthy and ill birds, in an
environment contaminated with Pasteurella
organisms. Environmental correlates Stress
appears to be an important factor in breaking
down the bird's resistance. Cold, damp weather
predisposes birds to this disease and outbreaks
are generally seen during the winter months in
overwintering waterfowl flocks.
Symptoms Convulsions, uncoordinated fluttering,
stiffness and rapid breathing. Respiratory
sound, sneezing and sticky nasal discharges are
sometimes observed.
Treatment/Management reduce population
build-ups, drain infected areas, kill infected
populations - controversial! Human concerns
not transferred to humans
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Avian Botulism- toxin produced by Botulinum
anaerobic bacteria The Salt Lake Tribune Article
Last Updated10/05/2006 125237 AM MDT    Utah
wildlife officials are reporting that an outbreak
of type C avian botulism has killed between
10,000 and 15,000 ducks and shorebirds statewide,
with the majority of the dead birds on marshes of
the Great Salt Lake.    "During an aerial count
in the middle of September, we estimated about
6,000 dead birds," said Tom Aldrich, (DWR).
Ecological Correlates High temps and lots of
decaying meat as bacterial food source,
fluctuating water levels, pesticide kills,
etc. Transmission Waterfowl ingest toxin from
substrate or ingest maggots that magnified
toxin concentrations Other Symptoms paralysis
of infected animals Treatment/Management
Control amt of decaying matter Control water
fluctuations Remove carcasses rapidly Remove
powerlines over water (collision kills)
Human concerns toxin destroyed in
cooking meat
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Avian Plague (Duck Viral Enteritus) (DVE) Herpes
virus - Entered US in 1972, cases growing
since. Differentially impacts specific
species pintails resistant, blue-winged teal
highly susceptible Ecological
correlates not known Symptoms Listless,
loss of appetite, bloody discharge from the
bill and vent, watery diarrhea Transmission
contact Treatment/Management Contain or
destroy infected flocks controversial!!!
Text example in California Human concerns not
transferred to humans
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Lead Poisoning
In waterfowl a dose as small as 1 pellet can
result in anemia, while 5 or more pellets can
result in death due to heart attack or muscle
paralysis. Symptoms lowered food intake,
weakness, weight loss, drooping wings, inability
to fly, and green watery diarrhea. Necropsy may
reveal a cracked, green-stained, peeling gizzard
lining, with or without lead shot present.
Treatment/Management Chelation of infected
birds (lead-binding chemicals). Shift to steel
shot has greatly reduced this in USA Fishing
sinkers still problematic MERCURY Great Salt
Lake For teal and shovelers, adults should eat
no more than two 8-ounce meals per month, and
young children and women who are pregnant or may
become pregnant should have no more than one
4-ounce meal per month, the advisory says. Women
of child-bearing age and children should not eat
goldeneye at all, while other adults ought to
limit their consumption to one 8-ounce meal of
goldeneye a month.
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Note that symptoms for differing diseases often
similar e.g. Avian botulism, cholera, DVE, lead
poisoning,
Spasmodic twitching and muscle quivering, body
trembling. Convulsions and/or blind staggers.
Jerkiness in gait, tremors, and
convulsions Convulsions, uncoordinated
fluttering, stiffness and rapid breathing,
listlessness, shivering Listless, loss of
appetite, may have a bloody discharge from the
bill and vent, develop a great thirst and exhibit
a watery diarrhea. Uncoordinated walking,
weakness, lethargy, tremors, and abnormal head
posture
Often disease may have key symptom, but not
always expressed
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Aspergillosus Fungal
Ecological correlates moisture favoring moldy
grain, grass
Transmission Inhalation of fungal spores
Symptoms Weak, emaciated, gasping, fungal
tissue in respiratory tract Treatment/management
removal of moldy food sources (bird
feeders, crops in fields) Human Concerns can
inhale spores from air sacs but usually dangerous
only to those already immunocompromised
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Avian Influenza (Bird Flu)
Free-living birds in the orders Anseriformes
(ducks, geese, swans) and Charadriiformes (gulls,
terns, shore birds) have traditionally been
considered the natural reservoirs for avian
influenza viruses (AIVs) Before 2005, no
evidence that highly pathogenic avian influenza
(HPAI) was maintained in wild bird
populations. In 2005, outbreaks involved large
numbers of wild birds with subsequent spread of
viruses to Europe and Africa probably by
migratory birds. Many types of AIVs, only some
highly pathogenic. Low pathogenicity types
present in most birds. HPAIVs may kill large
numbers of domestic birds and potentially humans.
Management Monitoring and rapid response in
destroying infected birds
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What are these suffering from? They look healthy
to me
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Could be suffering Brucellosis Early
malnutrition Early chronic wasting disease Liver
flukes Lungworm Tapeworm Or a host of others!
So not all animals, not all diseases show
symptoms at all times See text for this
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• Ultimately a manager must determine the role
  disease plays in the system they are managing by
  answering several basic questions
• Is it an important, natural, density dependent
  factor (dashed line) or is it density independent
  (solid line)?

If density dependent could indicate crowding or
increased stress in small populations
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2. Does it affect the overall population health
in a positive way? (the tapeworm-moose-wolf
interaction described in text)
Wolf feces with tapeworm eggs.
Contaminate forage water
Wolf
Moose Tapeworm forms cysts in
lungs Worse the older the moose gets
Wolf eats moose, ingests
Result Wolves prey more on older moose!
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• Is the disease an unnatural event due to human
  alteration of habitat, vectors,
• population densities or other factors?

• Does the disease threaten the health or viability
  of populations of special concern?
• (e.g. Parvovirus and wolves, distemper and
  black-footed ferrets)