SUMMIT, N.J. – The parasite, Cooperia, has become the most prevalent internal parasite in U.S. cow-calf operations according to research data from USDA’s National Animal Health Monitoring Service (NAHMS) Beef 2007-2008 cow-calf survey. The effects of Cooperia on cattle productivity, however, have largely gone unchecked. Fortunately, a newly published research study – completed by leading U.S. parasitologists and sponsored by Merck Animal Health – brings to light the negative impact Cooperia can have on productivity if a deworming program is leaving these worms behind.
New enemy Number 1
As part of the 2008 National Animal Health Monitoring Service’s (NAHMS) cow-calf study, USDA-ARS researchers sought to not only identify animals harboring internal parasites, but also get an indication of which parasites were actually present and still shedding eggs after treatment with common dewormers.
“Using DNA-screening methods, we identified which parasites were left behind in the cattle groups with less-than-effective dewormer treatments. In two out of every three herds showing poor efficacy, only certain worms were left behind,” said Bert Stromberg, Ph.D., professor of parasitology at the University of Minnesota. “A large portion of the animal groups with low efficacy contained Cooperia (small intestinal worms) after deworming, which would be indicative of tolerance to a particular anthelmintic treatment by that parasite.”
For decades, the brown stomach worm – Ostertagia (O. ostertagi) – was believed to be the most pathogenic and economically costly of cattle gastrointestinal parasites, explains Stromberg. And to their credit, avermectin dewormers have done a good job of controlling these performance-robbing parasites.
“But over time, the constant removal of drug sensitive and highly immunogenic species such as Ostertagi was favoring the colonization and retention of less immunogenic but avermectin-resistant genera such as Cooperia punctata,” said Stromberg.
“The effect of Cooperia on cattle productivity was largely unknown. It was long considered a non-factor,” explained Lou Gasbarre, parasitology consultant and former research lead from USDA’s ARS Bovine Functional Genomics Lab in Beltsville, Ma. “This study was conducted to look specifically at the impact of Cooperia on cattle productivity.”
In the Fall of 2009, two hundred calves with an average weight of 460 pounds were acquired from Northwestern Arkansas and Northeastern Oklahoma and, upon arrival, were vaccinated and drenched with fenbendazole and given levamisole according to label directions. Animals were preconditioned for approximately one month and fed a standard growing ration. At four weeks, all calves were dewormed through their feed using fenbendazole, re-vaccinated, and moved to pens equipped with GrowSafe® system feed bunks. After an additional week to get acclimated, calves were randomly divided into two groups of 80, and each group was further divided into two replicate pens of 40 calves.