The Role of Wildlife in Animal Disease
While many livestock and poultry diseases
can be researched and controlled exclusively by working with the specific
animal of concern, others can only be understood by incorporating wildlife into
the research and risk assessment.
For example, raccoons serve as a source of
rabies infection in the Midwest, while birds play a key role in the
transmission of West Nile virus to horses and humans. ARS studies the role of
wildlife in several diseases important to agriculture: tuberculosis,
brucellosis, lyme disease, malignant catarrhal fever, transmissible spongiform
encephalopathies, pine needle abortion, avian influenza, and Newscastle
In some cases, wild animals serve as a
direct reservoir for the infectious agent. Bison and elk in Yellowstone
National Park carry the bacterium that causes brucellosis in cattle. In 1956,
124,000 cattle herds tested positive for brucellosis. This year, there are no
known cattle herds with brucellosis thanks to a cooperative USDA and state
eradication program. But as long as bison and elk serve as havens for the
bacteria, theres always potential for the disease spilling back over to
Other eradication programs, such as for
bovine tuberculosis, also suffer from wildlife carriers. The existence of these
diseases causes trade barriers. These barriers wont be overcome until the
disease is not only eradicated from livestock, but scientists can devise
methods to prevent reintroduction from wildlife.
Studying wildlife also helps researchers
assess the risk that a disease will spread. Avian viruses such as those that
cause influenza, Newcastle disease, and avian pneumovirus can pass back and
forth between wild and domestic birds. But only some virus strains cross
species. By understanding which viruses are likely to spread with wild birds,
researchers can develop strategies to reduce exposure and
Also, when scientists identify a new virus
in poultry, they can look at their data on wild birds to help discover the
virus origin, as well as the likely direction in which it will
And the research may one day help local
economies. For example, deer infected with tuberculosis in Michigan and elk
with chronic wasting disease in the West create hunting-related restrictions
that greatly dampen local economies as well as threaten agriculture. MCF
affects many animal species, especially exotic deer and related animals in
Research on chronic wasting disease may help
define if and how a prion disease can cross species-- key to overcoming trade
issues associated with spongiform encephalopathies and helping to ensure that
the United States remains BSE-free.
Because wildlife and the diseases they carry
do not observe human boundaries, ARS has a key national research role--along
with the USDAs Animal and Plant Health Inspection Service--to help state
agricultural agencies manage disease outbreaks. ARS also has the containment
facilities that allow them to study infected animals and the disease agents, as
well as veterinarians with specific expertise in these diseases.
For more information on ARS wildlife disease
Diana Whipple or
Keith Murray, (515)
Knowles, (509) 335-6022
David Swayne, (706)
ARS scientists have
cracked the biochemical
code of the chicken herpesvirus that causes Marek's disease--that could
help in creating new vaccines against the poultry disease.
Piglets grew about 12
percent faster in their first 18 days of life than did other pigs when they
were given a one-time injection of the anti-inflammatory agent dexamethasone,
according to ARS research.
Measuring immune system messengers--called
basic questions about how pigs and cattle respond to infection or stress.
Researchers can use information from this ARS research to design targeted
therapies that stimulate the desired response.
An ARS research project to determine the
anaplasmosis, babesiosis, and theileriosis in Morrocan livestock will help
producers in that country as well as help standardize testing procedures for
these diseases internationally.
ARS' patented "four-poster" device is the basis
for controlling ticks
on white-tailed deer in the Northeast. In Maryland, populations of
blacklegged tick nymphs
dropped 59 to 71 percent.
J. Mathews Pound
ARS animal ethologists hope to
help prevent accidental
crushing behavior in pigs and encourage less agressive behavior in cattle
while feeding. They are seeking clues to these behaviors by undetected
observation of the animals.
New clues about the role of hormones and genetics
in birth weight may
help reduce dystocia in heifers. ARS research on birth weight, feeding, and
sire contribution have already helped breeders greatly reduce the
These ARS researchers have been honored recently
for their achievements:
ARS Honor Awards:
Mohammad Koohmaraie ,
Meat Animal Research Center, for developiing
first rapid tests for detecting pathogens on beef, pork, and poultry carcasses,
as well as techniques for reducing E. coli O157:H7 in red meat.
S. Karl Narang and
Southeast Poultry Research Laboratory, as part
of the West Nile Virus Team, for outstanding and dedicated efforts in
developing a strategy for addressing issues related to surveillance,
diagnostics, and prevention of the West Nile Virus in the Western Hemisphere .
Mitchell, Southeast Poultry Research
Laboratory, received a
Consortium award for designing an electrostatic space charge system that
removes dust and microorganisms from the air of poultry-producing facilities.