Wildlife Diseases

Are you prepared to be grossed out?

Disease:

Any departure from health

Classification

• Infectious

• Parasitic

• Toxic

• Physiological

• Nutritional

• Congenital

• Degenerative

Infectious

Caused by pathogens

• Bacteria

• Viruses

• Rikettsiasa

• Parasites

• Fungi

Bacterial Diseases

Avian BotulismClostridium botulinum, an anaerobic bacterium

Major Botulism Outbreaks in N.A.

Avian Botulism

1. Inability to fly—’steaming’

2. Paralyzed nictitating membrane

3. Paralysis of neck muscles; can’t hold head erect; drowning

Rickettsia

• Bacterial, intracellular parasites

• All transmitted by arthropod vectors

• Humans are accidental/incidental hosts

Rickettsiae  

Disease Organism Vector Reservoir

Rocky Mountain spotted fever

Rickettsia rickettsii Tick Ticks, wild rodents

Ehrlichiosis Ehrlichia  chaffeensisE. erwingiiAnaplasma phagocytophilium

TickDeerDeerSmall mammals

Rickettsialpox R. akari Mite Mites, wild rodents

Scrub typhus R. tsutsugamushi Mite Mites, wild rodents

Epidemic typhus R. Prowazekii Louse Humans, squirrel fleas, flying squirrels

Murine typhus R. typhi Flea Wild rodents

Q fever Coxiella  Burnetii None Cattle, sheep, goats, cats 

Rocky Mountain Spotted Fever

American dog tick (Dermacentor variabilis)

Rocky Mountain Spotted Fever

The ‘spots’

•Most common rickettsial disease in US

•Principal reservoir is a hard tick

•Most cases April-September

•Inactive rickettsia are warmed by blood meal, get into saliva; hence, prolonged bite increases transmission likelihood

•Wild rodents infected, but not main reservoir host

•Symptoms: abrupt onset of fever, chills headache and myalgia usually 2-12 days after the bite

•Mortality rate in untreated patients is 20%

Parasitic Diseases

Parasitic Life Cycles

• Several different kinds of hosts– Definitive– Intermediate

• Reservoir• Dead end

• May be endo- or ectoparasites

Ichthyophthirius

A ciliated protozoan

Black Spot/Black Grub

•complex life cycle requires fish-eating birds or mammals, snails, and fish at different stages

•encysted larval stage of one of several flukes

•even heavy infestation do relatively little damage unless on gills, eyes, or very young fish

Botfly life cycle

Tapeworm

Taenia pisiformis

Taenia pisiformis

Cysticercosis

• In rabbits, appears as conspicuous spots on the liver (sometimes confused with tularemia)

• Dogs and related carnivores are host to the adult tapeworm.  • Eggs are passed out of the body in the feces. • Rabbits are the major intermediate host; become infected when the

eat vegetation contaminated with the eggs.  • In digestive tract eggs develop into tiny free-moving parasites that

penetrate the gut wall and enter the blood stream where they are carried to the liver.  After traveling through the liver tissue for a number of days, they break through the liver wall and enter the abdominal cavity.  There they attach to the surface of various abdominal organs and complete development into cysts. 

• The cyst stage is as far as these tapeworms develop in rabbits.  If eaten by a dog or other suitable carnivore, the tapeworms will then continue their development to maturity.

Sarcoptic Mange

Sarcoptes scabiei •mite parasites of squirrels, rabbits, foxes, dogs, humans, and many other mammals

•larvae and adult mites eat skin cells from their hosts

•mate on the surface of the host's skin

•cause allergic reaction w/intense itching and often bald spots

•often leads to secondary infections

Deer Liver FlukeFascioloides magna

•Often fatal in sheep

•In cervids, are encapsulated, thus restricting migration

•Usually fairly well tolerated in deer

Whirling Disease

• introduced from Europe• serious problem in hatcheries• pathogen is Myxobolus cerebralis, a metazoan parasite• penetrates the head and spinal cartilage of fingerling

trout where it multiplies very rapidly, putting pressure on the organ of equilibrium

• causes the fish to swim erratically (whirl), and have difficulty feeding and avoiding predators

http://upload.wikimedia.org/wikipedia/en/4/45/LifeCycle%28Myxobolus_cerebralis%29.jpg

GapewormSyngamus trachea

Male and female gapeworms entwined in tracheal lumen

•Inhabit trachea of wild and domesticated birds

•Infection can be direct (eggs or larvae) or by eating a host (earthworms, snails, slugs, flies)

•Not a problem of confined birds, but can be serious in free ranging birds (so much for free range chicken!)

Toxic Substances

• Pesticides– Chlorinated hydrocarbons a.k.a. organochlorines

• Lipophilic, attack CNS, persistent, mobile, biomagnify; some may mimic action of sex hormones

• Examples: DDT (banned), aldrin, dieldrin, endrin, chlordane, heptachlor, toxaphene (banned)

– Organophosphates• Less persistent than organochlorines• Associated with secondary poisoning, e.g., hawks die after eating poisoned

grasshoppers (the target species)• Examples: malathion, parathion; inhibit acetylcholinesterase

– Carbamates• Less persistent, hence less biomagnification; also inhibit Ach-ase• Example: Fenoxycarb-inhibits insect metamorphosis; Temic. Sevin. Furadan

– Bacillus thuringiensis (Bt)-not toxic to animals, but may affect their prey, e.g. silkworm moths and Whip-poor-wills

Toxic Substances

• Herbicides– Of course, animals are non-target species;

may have direct toxicity or indirect effects such as defoliation

– Examples:• Trifluralin (mallards)• 2, 4-5 T-little effect on mallards• Paraquat-very significant effects

Mercury Poisoning• used in the past as the active ingredient in ointments, parasiticidals,

antiseptics, disinfectants, diuretics and fungicides • A current major source is coal-burning power plant emissions• accumulates in fish and fish-eating animals. Inorganic mercury

which enters a water source is readily converted to methyl mercury by aquatic microorganisms and accumulates in the tissues of fish. The common loon, mink and otter have been poisoned by mercury as a result of ingestion of mercury contaminated fish.

• reported to cause abnormal egg laying behavior, impaired reproduction, slowed duckling growth, and altered duckling behavior in mallard ducks. Occasionally seed eating birds are affected by mercury toxicity after feeding on mercury fungicide treated seed.

Lead Poisoning• Today is the result of ingestion of spent lead shot or

fishing sinkers and jig heads during normal feeding activities.

• When the lead reaches the acidic environment of the gizzard (ducks, geese and swans) or the ventriculus (loons), it is worn down, dissolved, and absorbed into body tissues.

• Also been noted in small mammals (raccoon) and raptors, presumably from the ingestion of lead contaminated prey.

• Once the lead reaches toxic levels in the tissues, muscle paralysis and associated complications result in death.

• Mimics the movement of calcium.• Signs include lowered food intake, weakness, weight

loss, drooping wings, inability to fly, and green watery diarrhea.

• mortality directly due to lead poisoning may be secondary to the losses due to "non-lethal" effects of lead such as reproductive problems, increased susceptibility to disease and infection, and increased predation due to anemia and weakened muscles.

• The switch from lead to non-toxic shot has significantly reduced the number of birds dying from lead poisoning in the U.S.

Others of Interest

• Brucellosis in bison

• Epizootic hemorrhagic disease

• Tuberculosis

“New” Diseases

• Conjunctivitis

• West Nile Virus

• Lyme Disease

• Spongiform encephalopathies– Mad Cow Disease– Chronic Wasting Disease

Transmission to Humans

• Lyme Disease

• Sylvatic (bubonic) Plague

• Tularemia

• Rabies