The first preclinical, noninvasive test for scrapie, a fatal brain disease of sheep and goats, should be available in a few years, thanks to ARS research. Reliable diagnosis of scrapie is the first step to eradicating the disease, which would greatly improve U.S. sheep and goat export opportunities. ARS scientists discovered that the nictitating membrane, or third eyelid, in sheep collects proteins known as prions. Abnormal prions are the infectious agents believed to cause scrapie. Until now, scrapie could be confirmed only by examining the brains of dead animals. The researchers also developed a new laboratory-built molecule, called a monoclonal antibody, that detects the presence of the abnormal prions. The test will eventually allow veterinarians to detect scrapie before animals show clinical signs. Only a local anesthetic is needed to sample the eyelid tissue, so the procedure will be inexpensive and safe. ARS has applied for a patent on the test. (PATENT APPLICATION 08/950,271)
Animal Diseases Research Unit, Pullman, WA
Donald P. Knowles, (509) 335-6022, dknowles@vetmed.wsu.edu

New tests to accurately diagnose and identify all known strains of Chlamydia bacteria that infect birds, humans and other mammals have been developed by ARS researchers. In humans, Chlamydia cause sexually transmitted diseases, respiratory disease and eye infection leading to blindness. In animals, the bacteria cause respiratory disease, conjunctivitis, arthritis, enteritis and reproductive failure. In birds, chlamydial infection results in lethargy and sometimes death. Until now, the only way to study these bacteria has been in cell cultures or fertilized chicken eggs. The four DNA-based tests use polymerase chain reaction (PCR) to target genetic material found in all chlamydial strains. One of the tests takes only about 4 hours, compared to 2 to 4 days needed by current culturing methods. The new tests will help veterinarians diagnose and improve treatment for sick birds and animals. Most important: They will shed light on how people and animals become infected. ARS is pursuing patents on these tests.
National Animal Disease Center, Ames, IA
Arthur A. Andersen/Karin D.E. Everett, (515) 239- 8338/8414, aanderse@nadc.ars.usda.gov, keverett@nadc.ars.usda.gov

An intestinal parasite that feeds on the blood of sheep, cattle and other ruminant animals could become its own worst enemy. That's if ARS researchers can exploit important biochemicals in the parasite's own gut that help it digest red blood cells. One possibility: a vaccine that could help "jump-start" the immune system of susceptible or young animals, like lambs or calves. Currently, anthelmintic drugs are the weapon of choice against the parasite, the nematode Haemonchus contortus. Also called the barberpole worm, H. contortus belongs to a genus that costs cattle and sheep producers millions of dollars in losses and control measures. The barberpole causes bleeding in its host's stomach walls, then feeds on the blood. Severe infections can kill an animal or cause poor milk, meat, hide or wool production. The worm mainly derives its nutrition from hemoglobin in red blood cells it ingests. Scientists recently found several key proteins and enzymes that help the barberpole utilize these nutrients. One protein group, called hemolytic factors, ruptures the red blood cells. This causes hemoglobin to seep out into the barberpole's digestive system. In test tube studies, the hemolytic proteins completely destroyed sheep red blood cells within 90 minutes after exposure. Researchers want to purify the proteins so their chemical structures can be ascertained. This raises the prospect for developing antibodies to help animals stave off nematode infection and ease the need for anthelmintic drugs.
Parasite Biology and Epidemiology Laboratory, Beltsville, MD
Ray Fetterer, (301) 504-8300, rfetterer@ggpl.arsusda.gov

A high-tech molecule called a bifunctional antibody may give cows a natural way to fight mastitis, an infection of the mammary gland. The first of these antibodies for farm animals has been built by an ARS researcher with help from researchers at the National Institute for Agronomic Research in Nouzilly, France, and the National Cancer Institute in Bethesda, MD. Mastitis costs the U.S. dairy industry more than $2 billion annually. A producer with 100 cows can expect some 50 to 80 cases of mastitis each year. Antibiotics are often ineffective. Producers can't sell milk from treated cows for a few days. To find a more natural alternative, the ARS scientist turned to the bifunctional, or coupled, antibodies. One end of the new antibody hooks to the mastitis-causing bacterium, Staphylococcus aureus. The other end snags its "terminator," a neutrophil--a specialized white blood cell from the cow's immune system. This triggers the neutrophil to release a lethal spray of hydrogen peroxide. The spray can't miss, since neutrophil and bacterium are "handcuffed" together by the antibody. It could take several years to ready the technology. Scientists must first prove bifunctional antibodies adequately boost the neutrophils' killing power. Then they will have to refine the technology for its most effective use by dairy producers.
Immunology and Disease Resistance Laboratory, Beltsville, MD
Max Paape, (301) 504-8302, mpaape@ggpl.arsusda.gov

Newborn piglets respond to infection with unusual and possibly harmful changes in body temperature, while older piglets quickly develop a mild fever, one of the body's natural defenses against disease. In a laboratory maintained at about 64 F, scientists injected 1- to 28-day-old piglets with a component of killed bacteria to simulate infection by a live disease organism. Piglets 21 to 28 days of age produced fever within an hour, in contrast to newborns that developed hypothermia--reduced body temperature. This underscores the very young piglets' need for a warm environment. Further research may explain why newborn pigs with simulated or real infection develop hypothermia. An understanding of the physiological mechanisms may help scientists find ways to improve growth and reduce sickness and death among young pigs. About 12 to 15 percent of piglets now die before weaning.
Animal Physiology Research, Columbia, MO
Robert L. Matteri, (573) 882-1047, robert_matteri@muccmail.missouri.edu

A new oral vaccine that protects cattle against the pneumonia-causing bacterium Pasteurella haemolytica has been designed by ARS researchers. Pneumonia costs U.S. and Canadian cattle producers more than $1 billion each year. In laboratory and field tests, the genetically engineered vaccine--administered in feed--provided 100 percent protection for calves. In a field test of 100 calves, none of the vaccinated calves died while 10 unvaccinated calves died from pneumonia. Shipping fever, as this respiratory disease is more commonly known, affects animals about one week after they are transported from the cow and calf operations where they were born to the feedlots where they finish their growth. An added bonus: Vaccinating calves via feed rather than by intramuscular injection is less stressful for animals and less time consuming for producers. This research was supported by the Biotechnology Research and Development Corporation.
National Animal Disease Center, Ames, IA
Robert E. Briggs, (515) 239-8280, briggs@nadc.ars.usda.gov Fred M. Tatum, (515) 239-8236, ftatum@nadc.ars.usda.gov