ARS' Approach to Scrapie and Other TSEs:
Long-Term Research and Practical Tools
On a day-to-day basis, sheep producers worry
much less about scrapie than about predator control and foot rot. Cattle and
dairy producers likewise focus their disease-control efforts on Johne's disease
and mastitis rather than on diseases not present in the U.S., such as bovine
Nevertheless, scrapie, BSE and other
transmissible spongiform encephalopathy (TSE) diseases rank high among concerns
of all livestock producers. That's because in our global economy, the fear or
threat of an emerging disease can hamper operations almost as much as an actual
To help address the long-term needs of the
U.S. animal industry, Agricultural Research Service
laboratories in Ames, Iowa and
Pullman, Washington have been conducting
long-term studies on TSEs and aberrant prions, the form of protein believed to
cause these diseases. ARS' goal to provide researchers and producers with tools
that will help them protect their animals, improve trade opportunities and
maintain public confidence in our food supply.
ARS researchers just announced a
promising test that
appears to detect prions in blood. The test needs further validation, but it
could be the first blood test to indicate a possible TSE. Further along in the
regulatory chain are monoclonal antibody-based tests that detect prions in
specific tissues of mammalian species. Other accomplishments include the first
non-invasive test for scrapie and ongoing studies of the relationship between
genetics and susceptibility to becoming ill with scrapie.
Scrapie, a fatal, neurological disease of
sheep and goats, has been recognized for more than 200 years. The first case in
the United States was identified in 1947. Scrapie-infected animals have never
been linked to human disease. Chronic wasting disease, a recently discovered
TSE that affects elk and mule deer, as well as transmissible mink
encephalopathy, have also been present in the U.S.
BSE, a similar spongiform disease that
affects cattle, first appeared in England in the mid-1980s. Since then, a new
variant of an existing human spongiform encephalopathy, Cruetzfeldt-Jakob
disease, also appeared in England.
Although BSE has never been detected in the
U.S., its presence in Europe--and fears of its presence elsewhere--have created
international trade barriers affecting most livestock producers.
For this reason, as well as the actual
disease incidence caused by scrapie, U.S. producers are anxious to eliminate
ARS began working on scrapie and mink
encephalopathy in the mid-1980's. Their research contributed to the knowledge
that the TSEs could be transmitted across species, and that the disease agent
was highly resistant to destruction.
ARS strengths in the TSE arena include
- Large, secure containment facilities that
allow researchers to work with large numbers of animals, and
- Cooperative agreements with regulatory
agencies that give scientists access to scrapie-positive animal tissues.
ARS performs high-risk, long-term research
projects spanning several years, a crucial support for TSEs, which typically
take several years to manifest in an animal.
Researchers today have a greater opportunity
than ever to understand TSEs and to manage--and eventually eliminate--their
threat. ARS scientists will continue to play a major role in that effort.
For more information about ARS research on
scrapie or other transmissible spongiform encephalopathies, contact
Randall Cutlip or Donald Knowles.
ARS researchers are using genetic analysis and
clinical tests to distinguish weak Newcastle
strains from virulent strains. The techniques can provide an early warning
system for the poultry industry.
Daniel J. King and
Bruce S. Seal, (706)
A new ARS-developed laboratory test provides the first single genetic test
that distinguishes all five types of bluetongue viruses found in the U.S.
Other new tests identify epizootic hemorrhagic disease viruses.
William C. Wilson and
James O. Mecham, (307) 766-3600
ARS researchers are developing a
vaccine to protect fish
from Streptococcus iniae, along with health management guidance that
may help replace use of antibiotics.
Philip H. Klesius, (334)
Richard L. Witter was
inducted into the ARS Hall of Fame in September for his career-long
contributions. He lead scientific teams that discovered the cause of Marek's
disease and developed vaccines and other control measures for Marek's disease
and avian leukosis. Witter works at the ARS Avian Disease and Oncology
Laboratory in East Lansing, Mich.
Richard L. Witter , (517) 337-6828
Cattle, sheep and goats
prefer alfalfa hay
harvested in the afternoon, according to ARS research. Apparently, the
animals discriminate on the basis of total nonstructural carbohydrates.
Mayland, (208) 423-6517
FANS, or fan assessment numeration system, is an
ARS-designed measurement tool that can
pinpoint the best
location for fans that ventilate animal barns and poultry houses.
John Simmons, (662) 320-7480
Hog farmers may be able to
breed pigs with a
natural resistance to edema disease by using a genetic test developed by
ARS and the Pig Improvement Company of Franklin, Kentucky. ARS and other
researchers previously discovered genetic influences over resistance and
susceptiblity to E. coli F18, which causes the edema.
Julia Ridpath, (515)
new oral vaccine for
cattle shipping fever developed by ARS scientists could be available within
3 years. The oral dose is highly effective and protects animals within 4 days
rather than the 10-14 days needed by current injectable vaccines.
Robert E . Briggs and
Fred M. Tatum, (515) 663-7639
feeder developed by ARS scientists releases a self-adjusting collar to the
animals when they feed. The goal is to equip deer with tick-repellant collars
to help reduce Lyme disease in the northeast and control cattle fever ticks
along the Texas-Mexico border.
Pound, (830) 792-0342
PEMS, or Poult Enteritis Mortality Syndrome,
strikes first in the
thymus,or lymphoid glands of turkeys, discovered ARS and North Carolina
State Univerity researchers. The scientists are now trying to identify the
virus they isolated from a turkey thymus to help determine the cause of PEMS.
Stacey Schultz-Cherry and
David Swayne, (706) 546-3432
A single injection of a hormone orexin-B into
3-week-old pigs increased feed intake 18
percent, but only for a short time. Researchers hope to devise synthetic
hormones and other strategies to help piglets thrive.
Robert L. Matteri, (573)