A team of USDA and university researchers has demonstrated that when a bacteria-derived protein was fed to worm-infected swine, the infection was nearly completely eliminated.
Intestinal parasitic roundworms are host-species specific and are found in pigs, cats, dogs, humans, and other animals. The parasitic roundworm that commonly infects pigs is called Ascaris suum,
The research team included microbiologist Joseph Urban and his colleagues at the Agricultural Research Service's Beltsville, Md., Human Nutrition Research Center and Raffi Aroian and Yan Hu at the University of California-San Diego.
In its experiments, the team used a crystal protein called "Cry5B," provided by Aroian's group, which is derived from the soil bacterium Bacillus thuringiensis. Cry5B protein is considered nontoxic to vertebrates and mammals, but it has been used in the past as an insecticide. Ascaris suum genetically expresses receptors for Cry5B.
Previously, Cry5B had been shown by Aroian and colleagues to be toxic to hookworms. In laboratory tests, Cry5B triggered activation of stress-response pathways in Ascaris larvae and adults similar to that observed with other worms.
"Feeding two moderate doses of Cry5B to pigs resulted in nearly complete elimination of intestinal A. suum infection, and all intestinal roundworm larvae were damaged or destroyed," says Urban. "The dosage we provided in this study is comparable to the dose range used in existing commercial antiparasitic drugs."
There is a need for more practical delivery systems for antiparasitic drug treatments, according to the scientists. Cry5B holds potential for use where worm resistance is becoming a problem, especially among ruminant livestock.
The University of California researchers have filed a patent application on the protein expression, and further cooperative research with ARS is being planned.
"These results show the potential of Cry5B to treat Ascaris infections in pigs and other livestock," says Urban.
Source: Rosalie Marion Bliss, USDA ARS