Cats are the most likely source of a parasitic Toxoplasma gondii infection on hog farms, a survey shows. This is a public health concern because humans can become infected through handling or consuming raw or undercooked pork containing the parasite. If a pregnant woman becomes infected with T. gondii, her baby could be born blind, mentally retarded or with other severe health problems. ARS and University of Illinois researchers surveyed 47 Illinois farms, checking feed, soil, water and blood samples of swine, cats and wildlife around the farms. Sixty-seven percent of the 300-plus cats checked showed signs of previous exposure to T. gondii. After becoming infected, a cat sheds millions of parasite eggs called oocysts in its feces for about a week. If the parasite-laden feces come in contact with swine feed, hogs can swallow the oocysts and become infected. The scientists' recommendation: Keep farm feed supplies covered and out of reach of wandering cats.
Parasite Biology and Epidemiology Laboratory, Beltsville, MD
J.P. Dubey, (301) 504-8128

A genetically-engineered protein provides a rapid, sensitive test for diagnosing in pigs the organism that causes human trichinosis. This disease is caused by eating raw or undercooked meat, generally pork, that contains the parasitic nematode Trichinella spiralis. The disease poses a public health risk worldwide. ARS scientists isolated a naturally-derived parasite protein, called an antigen, that triggers the body's immune system to send out antibodies to fight off the parasite. In field studies, the natural antigen detected 98 percent of the medically significant cases in experimentally infected swine. To improve the test, scientists have copied and produced the parasite's gene that makes the antigen. The improved antigen will aid the pork industry in making Trichinae-free pork available to consumers. In 1985, the National Pork Producers Council estimated that being able to assure consumers of trichinella-free pork would boost domestic demand by two percent and exports by 33 percent--gains worth about $450 million yearly to pork producers. (PATENT 5,422,263)
Immunology and Disease Resistance Laboratory, Beltsville, MD
Dante S. Zarlenga/H. Ray Gamble, (301) 504-8979/8300

A feed additive made from sugar beets could help poultry producers win the $300-million-a-year battle against coccidiosis in their flocks. Producers now try to control this parasite-related disease primarily with drugs. But the parasite's increasing resistance to the drugs has intensified the search for other weapons. Field tests have shown feeding chickens the additive betaine in combination with an anticoccidial drug can help alleviate the weight loss, poor feed efficiency and intestinal disorders associated with coccidia infection. While betaine is not believed to be directly toxic to coccidia, it interferes with the parasite's ability to infect the birds' intestinal cells. When chickens ate medicated feed containing 1.5 to three pounds of betaine per ton, intestinal invasion by the parasites was 50 to 90 percent lower than in birds not given betaine in the feed, and parasite development was significantly hindered. Another plus: Researchers say betaine also helps improve the birds' digestion of nutrients.
Parasite Biology and Epidemiology Laboratory, Beltsville, MD
Patricia C. Augustine, (301) 504-8428

Cows infected with the Neospora caninum may abort a calf once, but seldom a second time. So there's no reason to send the cow to slaughter. That's the latest word from researchers studying this new parasite, discovered and named by ARS researchers in 1988. Since then, N. caninum has been pinpointed as a major cause of dairy cattle abortions in several countries, including the United States, the Netherlands, Australia and New Zealand. In California, more than 25 percent of all dairy cattle abortions in the past five years were caused by N. caninum. Abortion can occur at any time during gestation. Sometimes calves are born weak and paralyzed and die within a week. Some heifers are born infected and free of symptoms, but subsequently give birth to infected calves. Cows that become infected and abort a calf remain clinically normal. ARS researchers have developed a test to diagnose neosporosis, but no vaccine or treatment exists.
Parasite Biology and Epidemiology Laboratory, Beltsville, MD
J.P. Dubey, (301) 504-8128

ARS researchers are staying one jump ahead of a relatively new bacterium that causes abortions in livestock and intestinal upset in people. In 1992, a Belgian scientist first identified and named Arcobacter, a close relative of Campylobacter. Both species require only a small amount of oxygen to grow, making culturing in the laboratory very difficult. Because of their close genetic relationship, they are confusing to laboratory diagnosticians. To help simplify identification, ARS researchers first developed DNA probes and then made primers to use in methods that make identification accurate and quick.
National Animal Disease Center, Ames, IA
Irene V. Wesley, (515) 239-8291

A new genetic probe has been identified that may be useful for detecting in cattle's blood and feces the bacterium causing Johne's disease, a killer of dairy cattle. No treatment is available for Johne's disease, so identifying and removing infected animals from the herd is the primary means of control. To help find those animals, researchers developed a diagnostic probe from a segment of genetic material, called DNA, from Mycobacterium paratuberculosis. The probe binds with M. paratuberculosis, distinguishing it from other related bacteria. Plans are to compare the probe's performance with IS-900, the diagnostic test now used by laboratories. Cows with Johne's disease have chronic diarrhea and suffer massive weight losses that inevitably lead to death. Some infected cows show no signs of disease, but spread the organism through their feces or to their calves via contaminated udders.
National Animal Disease Center, Ames, IA
Judith Stabel, (515) 239-8304

Simple and easy-to-use staining techniques have been adapted for use in studies of the form and structure of roundworms--physical characteristics that are obscure and difficult to evaluate. A liquid stain using silver nitrate identifies surface characteristics of roundworms that infect cattle and sheep. A second red stain, using carmine-propionic acid, highlights their internal cellular structure. Together, these two new staining techniques improve the efficiency of identifying these parasites that include trichostrongyloid and other nematodes that cause cattle and sheep ranchers losses of more than $400 million annually. Russian scientists from the K.I. Skrjabin Institute of Helminthology, Moscow, and ARS researchers developed the staining techniques and are the first to apply them to study surface characteristics of these roundworms. The techniques provide a low-cost yet powerful tool for diagnostic and systematic research of roundworms, and may eliminate the need for more advanced methods of microscopy not available in many laboratories. The tests also may be applied to other types of parasitic worms.
Biosystematic Parasitology Laboratory, Beltsville, MD
Eric Hoberg/Alexander Khrustalev, (301) 504-8588