Chapter 8Chapter 8Wildlife Wildlife DiseasesDiseases

Essentials of Disease in Wild Animals (2006)

Gary Wobeser DVM, PhD

CBS580: Veterinary Clinical Epidemiology

FW720: Epidemiology of Wildlife Diseases

Case 1

And who will scavenge the scavengers?

South Asian Vultures

“Conservationists say that the population of three species of Asian vultures has fallen by 97% in 12 years, and they are now at risk of extinction.” BBC News 2005

Loss of “Air burial” ritual Increase of canine rabies

National Geographic 2004

South Asian Vultures Who – 3 species of Old World Vultures (Gyps spp.)

Oriental white-backed Vulture (Gyps bengalensis)

Long-billed Vulture (Gyps indicus) Slender-billed Vulture (Gyps tenuirostris)

What – Course of non-specific illness followed by rapid death, renal pathology, gout

When – Early 1990’s to present Where – India, Nepal, Pakistan Why –

Why - Diclofenac treated cattle carcasses. Different feeding strategies, different physiologic/anatomical responses

How – Suspected effect on blood flow to kidney creating a vicious cycle of kidney damage

Vulture restaurants Rapid Test to Save Vultures Vulture Hatchlings

Case 2

Our birds have gone crazy

Regional epidemic of neurologic disease and death in Bald eagles and American coots (and other birds)

Who - >100 Bald eagles, thousands of American coots, small number of other species

What – erratic flight, inability to fly, crash landings, swimming in circles, inability to stay upright in water, staggering, unable to right self.

Clinical features of AVM in American coots When – Fall-Winter months, since 1994 Where – 12 lake locations in 5 states

AR, GA, NC, SC, TX Why - Avian Vacuolar Myelinopathy (AVM)

AVM

Why – Current theory: neurotoxin from blue-green algae Stigonemetales.

Epizootiologic studies of AVM in waterbirds

Failure to transmit AVM to Mallard ducks

AVM linked to Exotic Aquatic Plants and a novel Cyanobacteria Spp.

How – Mechanism?

Case 3

The worst wildlife die-off in recent

history

Since the winter of 2006 over a million bats have died in North America

February 2006 – a caver 40 miles outside Albany, NY photographed hibernating bats with a white substance on their muzzles. A few dead bats were seen

Winter 2006-07 – NY Dept. of Environmental Conservation documents a few hundred dead bats, bats behaving erratically, bats with white noses

Tennessee to New Hampshire and parts of Canada are seeing unprecedented numbers of dead bats 90-100% loss of bats per hibernacula

Signs white fuzzy substance on nose and other parts

Movement to cold parts of cave Decreased body fat Flight during day and cold weather

Species of insect-eating bats affected include LITTLE BROWN BAT Tri-colored Northern Long-eared Big Brown Small-footed Indiana (endangered) Cave Myotis Virginia Big-eared (endangered) Gray (endangered)

Geomyces destructans

Cold-loving fungus Associated with Arctic permafrost soils

Reproductive range overlaps year-round NE cave temperatures 35 and 59 Fahrenheit

Found in Europe Little effect on bats

Managing for WNS

Close caves and mines Designate bats as threatened species

Designate fungus as prohibited invasive species

Pathogen investigation Genome sequencing

Treat the pathogen Antifungals, antiseptics

Case 4

Under heavy gray skies one morning in August 1995, eight schoolchildren and their nature-studies teacher set off across a bean field in south-central Minnesota and walked straight into the middle of an environmental mystery. They were headed for a woodlot where they planned to spend the day sketching trees, but got no farther than a large pond halfway there. As the kids walked along an overgrown field road that skirted the edge of the pond, they encountered large numbers of young leopard frogs fleeing into the weeds as they approached. Scampering after the animals, the students caught first one and then another and then yet another that turned out to be grossly deformed. During the next 12 months, a wave of similar discoveries all but overwhelmed worried officials in St. Paul. By the fall of 1996, the Minnesota Pollution Control Agency had received more reports of deformed frogs than it could handle--more than 200 sightings around the state. The MPCA, which had hurriedly persuaded the Legislature to fund a preliminary study of the problem and had assumed responsibility for the investigation, was soon joined in its search by the U.S. Environmental Protection Agency, the National Wildlife Health Center, the Natural Resources Research Institute in Duluth, several independent academic scientists, and an influential but little-known federal toxicology laboratory called the National Institute of Environmental Health Sciences, which investigates threats to human health.Even before that fateful field trip five years ago, the scientific community knew that frogs and other amphibians were imperiled around the world. Frog populations were declining or disappearing, and the causes were not always apparent. Habitat destruction, ecosystem modification, global warming, pollution, ozone depletion, exotic species introductions, new diseases, and acid rain were all understood to be threats, though not equally discernible ones. Some frogs seemed to be prospering in heavily developed and polluted environments; others were going extinct in what appeared to be pristine surroundings. But the mere mention of a "human health risk" raised the stakes in everyone's eyes. From the outset, Minnesota's deformed frogs suggested that a dramatic alteration in the local ecosystem had taken place, one that had to be considered a potential problem for other species.

Since 1980, populations of hundreds of the world's estimated 5,100 amphibian species have been vanishing or declining in almost every part of the world, even in protected wildlife reserves and parks. In some locales, frog deformities (such as extra legs and missing legs), which usually lead to mortality, are occurring in unusually high numbers. Imagine you found this frog (above) in a pond on your property. On further investigation you discovered that over 30% of frogs in that pond have similar deformities. How will you determine what caused the deformities? (http://www.first2.org/resources/inquiry_activities/frog_activity.htm)

1 site2 sites3 sites4 sites5 or more

USGS

"The complex life-cycle of the parasitic trematode Riberoria ondatrae“Brandon Ballangée

Environment

Agent

Host

Disease

September 2010

Case 5

The Appalachian Elktoe

2006 NCWRC Press Release

Case 6

Disappearing Cervids

Chronic Wasting Disease

Transmissible Spongiform Encephalopathy Contagious neurologic disease Causes degeneration of the brain Emaciation, abnormal behavior, loss of body function, death

Currently found in 18 states and 2 Canadian provinces

Captive and wild Mule deer, black-tailed deer, elk, moose

Impacts?

Timeline www.cwd-info.org