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USDA finds sheep parasite treatment effective

by Wyoming Livestock Roundup

The U.S. Department of Agriculture (USDA) Agriculture Research Service (ARS) announced Dec. 9 a new treatment found to prevent anemia, weight loss, poor wool and meat production, as well as death in sheep due to parasites. Research scientists at ARS, in partnership with Virginia Tech and the University of Massachusetts’ Medical School, worked to solve the number one health problem in the U.S. sheep industry – infection by the parasite Haemonchus contortus (H. contortus). 

H. contortus background

                  Researchers share H. contortus is a blood-feeding gastrointestinal nematode known to have significant health consequences in sheep and goats, especially to young lambs and kids. The parasite infects the abomasum of ruminants, interfering with digestion and ultimately having poor effect on the animal’s overall health. 

                  The parasite was previously controlled with anthelminitics, a type of medicine used to kill worm-like parasites such as flukes, roundworms and tapeworms. However, researchers note resistance of H. contortus to anthelminitics after becoming available commercially, creating greater proportions of the parasite population that survive treatment. 

                  “The H. contortus parasite has developed resistance to virtually all known classes of anti-parasitic drugs,” says ARS Scientist Dr. Joseph Urban. 

                  The parasite reproduces within the affected animal, and fertilized eggs are passed from animal waste to the soil. Larvae grow and develop in the soil creating a cycle of infection as animals are infected with the parasite from the pasture. 

Treatment research

                  Regarding the cycle of infection, Urban notes, “This is a major problem and the newly-developed treatment is derived from bacteria normally found in the soil producing a protein which binds to receptors in the intestine of the parasite.”

                  The soil bacteria treatment has been shown as effective against gastrointestinal nematodes in mice, hamsters, dogs and pigs. This protein, called the Cry5B protein, binds to and disrupts the digestive system of invertebrates such as H. contortus. 

                  “The treatment will then kill the parasites and reduce debilitating infection in adult sheep,” Urban continues. 

                  Researchers tested the efficacy of this protein against H. contortus during both the larval and adult stage from a strain resistant to anthelminitics in goats and sheep. 

New treatment

                  The study found the Cry5B protein is potent and very effective in controlling H. contortus larvae development and affects adult parasites. With the first results of the study, scientists created a new Active Pharmaceutical Ingredient containing Cry5B called Inactivated Bacterium with Cytosolic Crystal (IBaCC) as treatment. 

                  IBaCC, a paraprobiotic, was found to significantly reduce H. contortus in sheep. Three doses of the medication cleared greater than 70 percent of the adult parasites present and 96 percent of female parasites. 

                  “When the treatment was given to infected sheep at Virginia Tech there was a rapid and dramatic reduction of parasite reproduction and survival, without any negative effect observed in the sheep,” said Professor of Parasitology at Virginia Tech’s Virginia-Maryland College of Veterinary Medicine Dr. Anne Zajac. 

                  Further research to determine the minimal effective dose and best delivery methods have been sparked by the initial study. 

                  This treatment is currently being reviewed by the U.S. Food and Drug Administration and will likely be commercially produced once approved, according to a USDA article on the research.              

                  Averi Hales is the editor of the Wyoming Livestock Roundup. Send comments on this article to

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