I thought this is a rather important topic for cattlemen - parasite resistance to dewormers. While I have provided programming to small ruminant producers about anthelmintic resistance, it is also an issue for cattlemen. If we keep using dewormers indiscriminately, we may lose the efficacy of these tools. To avoid the development of drug resistance by parasites, the treatments must be targeted for when they are most effective, and done as infrequently as possible.
Here are a few recommendations:
- Remember to weigh you cattle and administer the appropriate dose.
- Intensive grazing on wet pastures is ideal for worm transmission.
- Lightweight stocker calves are susceptible to several parasites.
- You must choose the proper dewormer, depending on which worm you're targeting.
- Worm bulls of any age; their hormones can depress immunity against parasites; and they have higher worm egg counts than the herd average.
- Another vulnerable group is first-calf heifers. They're still growing, feeding a calf, and more stressed than adult cows.
- Studies show benefits of deworming weaning-age calves at least two weeks before vaccinating, thus allowing them to mount a better vaccine response.
June 23, 2014
After two moderate doses of a bacteria-derived protein were fed to worm-infected swine in an experiment, all intestinal roundworm larvae in the swine were damaged or destroyed and the infection was nearly completely eliminated, according to U.S. Department of Agriculture (USDA) and University of California-San Diego scientists.
The research team included microbiologist Joseph Urban and his colleagues at the USDA Agricultural Research Service (ARS) Beltsville Human Nutrition Research Center in Beltsville, Maryland, and Raffi Aroian and Yan Hu at the University of California-San Diego. ARS is USDA's chief intramural scientific research agency.
The parasitic roundworm that commonly infects pigs is Ascaris suum, which is genetically similar to A. lumbricoides, a roundworm species that infects about 1 billion people worldwide. A. suum infection in pigs is considered a good model for A. lumbricoides infection in humans because of its similar migration through the body and to the intestines.
During the 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.
The dosage the team provided in the study is comparable to the dose range used in existing commercial antiparasitic drugs. The results show the potential of Cry5B to treat Ascaris infections in pigs and other livestock and to work effectively in the human gastrointestinal tract, according to authors. The team described the research in a 2013 article published in PLOS: Neglected Tropical Diseases.
There is a need for more practical delivery systems for antiparasitic drug treatments, according to the scientists, and further cooperative research is planned.
Read more about this research in the May/June 2014 issue of Agricultural Research magazine.