Research Targets Livestock
ARS uses various strategies to deal with
different arthropod-borne viruses (arboviruses) and parasites. Researchers
might seek to stop a pathogen a pest is carrying, treat a resulting disease or
focus on managing populations of the pest itself. They might take all of these
approaches and more.
An ARS National Program,
Pests of Animals and Humans (#104), addresses problems concerning a range
of insects, including ticks, flies and mosquitos. Researchers are concerned
with pests indigenous to the United States, while also seeking methods to
assess and suppress potential risks from invasive pests outside U.S. borders.
Arthropod-borne pathogens pose potential
risks for epidemic disease to the U.S. livestock industry. The presence of some
disease-carrying pests can lead to restrictions on the exportation of animals
and animal products from the United States, and can lead to higher prices in
the domestic market.
Screwworm flies' flesh-eating maggots
parasitize livestock, wildlife and humans. ARS researcher Edward F. Knipling
first developed a theoretical sterilization technique in 1937 to control the
screwworm. The technique involves irradiating male insects, then turning them
loose to mate with wild fertile female insects. These matings don't produce
fertilized eggs, so numbers of insect offspring drop dramatically.
Knipling demonstrated in the early 1950s
that the male screwworm could be sterilized. His colleague, Raymond C.
Bushland, proceeded to develop this idea, which eventually resulted in the
eradication of screwworms from the United States, Mexico and Central America.
Today, the technique is used worldwide to eradicate outbreaks of other pests
such as Mediterranean fruit flies and tsetse flies.
Researchers at ARS'
Livestock Insects Research Unit in Lincoln, Neb., are working to develop a
male-only strain of screwworms to mate with females in the wild. They are also
preserving screwworm germplasm and enhancing screwworm rearing for eradication
programs. A new field
diagnostic kit developed at the lab differentiates screwworm fly maggots
from similar fly species that are not so harmful to cattle.
Knipling is remembered as the "founding
father" of areawide integrated pest management (IPM). Realizing total
eradication is not feasible for most pests, he developed the concept of using
specific insect parasites, predators, and other tactics over a broad area to
keep pest populations below the point where they are a financial burden on
farmers and ranchers. Kept at low levels, pests are more responsive to
biological, rather than chemical control.
Livestock Insects Research Laboratory in Kerrville, Texas, the legacy of
these pioneers continues as ARS works to control the cattle fever tick with a
variety of methods. Research has identified two independent mechanisms by which
the ticks become resistant to a class of pesticides. The Kerrville scientists
are also developing and improving laboratory tests to
pesticide-resistant ticks. The scientists have patented an invention, known
as the four-poster,
that uses bait to lure deer to self-apply pesticide to their heads, where most
ticks feed. This device will help control cattle fever in the Southwest and
Lyme disease in the Northeast.
The Kerrville researchers are teaming with
scientists at the ARS Animal Disease Research Unit in Pullman, Wash., in
spearheading the first tick genome project. They hope to learn more about the
protozoa in the Babesia genus that causes cattle fever.
Arthropod-Borne Animal Diseases
Research Laboratory in Laramie, Wyo., is another ARS lab working to
diagnose and control domestic livestock diseases transmitted by arthropods.
Currently, the most economically important arthropod-borne disease of U.S.
livestock is bluetongue disease (BLU). The biting midge transmits BLU and the
related epizootic hemorrhagic disease (EHD) viruses to ruminant livestock. The
presence of BLU viruses in the U.S. has resulted in restrictions on the
movement of livestock and livestock germplasm to BLU-free countries. The
Laramie research unit is assessing the role of arthropods in the transmission
of these viruses and others, such as West Nile virus. They developed the first
single genetic test to distinguish all five types of the virus that causes
bluetongue in the U.S. and developed rapid tests that
bluetongue from EHD.
Pesticides and drugs used for the control
of pests and pathogens can pose threats to the health of animals and humans.
ARS is developing safe, effective and user-friendly methods to detect, monitor
and control pests in ways that are safe for the environment.
For more information, contact the
Philip J. Scholl,
John E. George,
Richard T. Mayer,