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United States Department of Agriculture

Agricultural Research Service

Healthy Animals Newsletter

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Issue 2, October 1999
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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 spongiform encephalopathy.

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 illness.

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 all TSEs.

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.

Research Briefs

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) 546-3434

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) 887-3741

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.
Henry F. 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) 663-7372

A 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

A patented deer 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.
J. Mathews 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) 882-1047

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ARS Animal Health Research Laboratories

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Last Modified: 2/6/2007
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