The USDA’s Agricultural Research Service (ARS) along with two universities, announced a treatment for a blood-feeding gastrointestinal nematode parasite causing anemia, weight loss, lethargy, low wool/milk/meat production, and death in infected sheep and other livestock.
Researchers at ARS, the University of Massachusetts and Virginia Tech, together worked to combat Haemonchus contortus (Barber’s pole worm), a parasite that infects ruminant animals’ stomachs.
The parasitic worm reproduces within the animal, and its fertilized eggs pass through the animal’s waste into the soil. The larvae then develop to re-infect other unsuspecting animals through moisture on the blades of grass, spreading the infection throughout a pasture and creating a cycle of infection. Depending on temperature and soil moisture, H. contortus larvae can survive up to six months in the pasture.
The parasite has developed resistance to virtually all known anthelmintics, making it difficult for U.S. sheep and goat producers to control the multidrug-resistant parasite.
“The H. contortus parasite has developed resistance to virtually all known classes of antiparasitic drugs,” said ARS Researcher Dr. Joseph Urban, who led the research team in testing and implementation of a paraprobiotic treatment to kill the parasite that causes H.contortus.
The study’s treatment employs Bacillus thuringiensis (Bt), a microbe commonly found in soil and used as a bioinsecticide. Bt forms crystals during the formation of new cells and is toxic to insects, beetles, roundworms, nematodes and other soil-borne insects. The crystal 5B (Cry5B) from Bt had previously shown anthelmintic activities against parasites of monogastric animals, but had not been studied in ruminants.
While the Cry5B crystal produced in its natural form was ineffective against H. contortus, the researchers developed a parabiotic form, an “inactive probiotic,” in which the crystals are still preserved. The procedure called IBaCC (inactivated bacterium with cytosolic crystals) was given to sheep infected with H. contortus.
Treated animals received 60 mg of the IBaCC-treated Cry5B, administered daily for three days. By 72 hours after the first treatment, the fecal egg count (FEC) was reduced by 91 percent. The total worm burden of treated sheep was decreased significantly, with female worms reduced by 95 percent.
In another experiment, a live genetically modified version of Cry5B was administered orally daily for four days at 40 mg. The FEC of treated animals was reduced by 94 percent three days after treatment, and at necropsy, the female worm population was significantly reduced by 98 percent.
“H. contortus is one of the most devastating parasites on earth for small ruminants, so obviously, these are incredibly exciting results,” said Raffi Aroian, lead researcher and professor at the University of Massachusetts Medical School.
While IBaCC was effective for sheep, results for the study were not as successful for goats. While Cry5B was effective on eggs obtained from infected goats, the parabiotic form did not effectively reduce the parasitic load from goats’ rumens. Researchers speculate it could be any number of factors, including the difference between doses or the differences between the treatment the goats received and the IBaCC administered to the sheep.
Parabiotics are not commercially available and are currently being reviewed by the U.S. Food and Drug Administration (FDA). Once approved by the FDA, the treatment will be available commercially.
“Paraprobiotics represent a new evolution and hope in dealing with a malignant and pervasive parasite,” said Aroian. “The development of new therapeutics for this issue has been extremely difficult to come by, and I look forward to watching this new advancement unfold in the global and domestic industry.” — Charles Wallace, WLJ editor