Test Herd, Then Treat to Avoid Parasite Resistance

ST. JOSEPH, MO – (May 5, 2010) – As instances of internal parasite resistance to deworming treatments are becoming more numerous among the country's cattle herds, it becomes apparent that herd managers must pay closer attention to the use of these valuable herd-health tools. Controlling parasites is a proven practice to improve performance in all stages of cattle production; however, both overuse and underuse of anthelmintics can lead to a resistance problem.

Overuse is the result of producers deworming too often, and underuse occurs when too little product is administered, according to Dr. Mac Devin, professional services veterinarian with Boehringer Ingelheim Vetmedica, Inc. "In a closed population, if you treat too frequently, the remaining worms are the only ones left to breed," he says. "Resistance increases with each generation. And if less than the labeled dose is given, again, this leaves too many survivors to pass on their resistant genes to the next generation."

To establish a resistance management program in your herd, Devin recommends, with the help of your herd veterinarian, first conducting a fecal egg count reduction test to detect if you have parasite resistance in your herd. Two tests are taken; after the first test, treat the entire herd, then come back in 14 days to take another count and then calculate the loss.

"Do this test on 20 percent of your herd, or 20 animals, whichever is less," he says. "We want to see a 90 percent fecal egg production reduction." Less than that would suggest a resistant population is present.

Secondly, herd managers should do a coproculture. Samples are incubated and then evaluated by a parasitologist to determine the composition of the nematode population.

With this information, cattle producers can determine the most effective program that will minimize the risk of resistance. To accomplish this, Devin recommends these steps:

• Keep your veterinarian involved in your parasite management program.

• Choose a dewormer with the greatest efficacy. Look at the active ingredient in the parasite control product because there are differences in persistence and efficacy. For example, CYDECTIN® is the only product in the moxidectin family, and it has label claims for longer persistence than some other endectocide anthelmintics for some nematode species.

• Never under-dose—follow label directions.

• Quarantine, test and deworm new animals before turning them out with the rest of the herd.

• Periodically rotate product chemistry according to your veterinarian's advice.

• Use strategic management practices such as good hygiene and rotation of pastures and/or animal species to reduce pasture contamination.

Of these steps, administering the full label dose to each individual animal is the most important, Devin says. "If you underdose, it allows more resistant worms to survive, and each generation gets more and more resistant."

CYDECTIN Residue Warning: when used according to label directions, neither a pre-slaughter drug withdrawal period nor a milk discard time is required. Meat and milk from cattle treated with CYDECTIN (moxidectin) Pour-On may be used for human consumption at any time following treatment. A withdrawal period has not been established for this product in pre-ruminating calves. Do not use in calves to be processed for veal.

Boehringer Ingelheim Vetmedica, Inc. (St. Joseph, Mo.), is a subsidiary of Boehringer Ingelheim Corporation based in Ridgefield, Conn., and a member of the Boehringer Ingelheim group of companies.

The Boehringer Ingelheim group is one of the world's 20 leading pharmaceutical companies. Headquartered in Ingelheim, Germany, it operates globally with 138 affiliates in 47 countries and approximately 41,300 employees. Since it was founded in 1885, the family-owned company has been committed to researching, developing, manufacturing and marketing novel products of high therapeutic value for human and veterinary medicine.

In 2008, Boehringer Ingelheim posted net sales of US $17 billion (11.6 billion euro) while spending approximately one-fifth of net sales in its largest business segment, Prescription Medicines, on research and development.

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