Combination of Dewormers: The Time Is Now!

Posted On February 18, 2017— Written By

Resistance to dewormers is a fact of life, and the situation has worsened greatly in recent years. Surveys indicate that most farms have worms resistant to at least two of the three major groups of dewormers. Many have resistance to all three groups, and some farms now have resistance to all available dewormers.

There is now very strong evidence that using a combination treatment is the best method for using dewormers and should be implemented immediately on all farms that have gastrointestinal parasite resistance problems.

  • In New Zealand and Australia, products are sold that contain a combination of dewormers, so only one product needs to be administered. In contrast, in the USA, no dewormers are yet sold in this formulation,  so the dewormers need to be bought and administered separately. This increases the cost as compared to the products available in these other countries. In the USA, the different groups of dewormers available on the market are not chemically compatible, thus they CANNOT be mixed together in the same syringe. Rather, they need to be administered separately, but can be given one immediately after the other. Products that contain a combination of dewormers as those available in New Zealand and Australia, however, are being considered by the Food and Drug Administration,
  • When using dewormers in combination, meat and milk withdrawal times will be equal to the dewormer used with the longest withdrawal time period.
  • All dewormers should be administered at the full recommended dose whether administered singly or in combination. Check the Parasite Control section of the NCSU Meat Goat Portal for recommended dewormer dosages and meat and milk withdrawal times.
  •  If using dewormers in combination, it is critical to maintain refugia; thus, one should be using a selective treatment approach based on FAMACHA© (see FAMACHA© section of the ACSRPC website for more information on this method and for further explanations of refugia). The presence of refugia is essential to realize the full benefits from combinations. In fact, if refugia are not maintained then you will not get the necessary dilution of the resistant survivors, and this will then lead to having multiple-resistant worms that can no longer be controlled with the combination treatment.
  • If the efficacy of your dewormers are >80%, it is possible you may not notice any difference in the clinical response of treatments when applied singly vs. in combination.
  • Any safety precautions that exist for a single dewormer will also exist when used in a combination. Nevertheless, there are no known additional risks with using more than one dewormer at the same time.

Additional information on this topic:  check the article written by Dr. Ray Kaplan, Professor of Parasitology, University of Georgia, College of Veterinary Medicine, in the  AMERICAN CONSORTIUM FOR SMALL RUMINANT PARASITE CONTROL Timely Topic, January 2017.