Fall is prime time for parasite control — but according to experts, routine deworming may be doing more harm than good.
At a recent Beef Cattle Research Council (BCRC) webinar, The Ins and Outs of Parasite Management, veterinary specialists Dr. John Gilleard (University of Calgary) and Dr. Carling Matejka (Veterinary Agri-Health Services) outlined a growing concern across Canada’s beef sector: parasite resistance linked to years of automatic, whole-herd treatments.
They urged producers to move toward a “test-and-target” strategy — one that focuses on assessing parasite load before treating, selecting the right product, and preserving the long-term effectiveness of available dewormers.
Why Resistance Is Rising
Gilleard explained that decades of routine endectocide use, particularly ivermectin, have accelerated resistance. Blanket-treating herds every season is no longer sustainable, he warned. Instead, producers should adopt an assess-first approach — testing for parasite presence and severity before deciding if and how to treat.
This shift helps preserve treatment effectiveness while reducing unnecessary drug use and costs.
Three Key Tools for Effective Control
The webinar highlighted three main tools for managing parasites sustainably:
-
Grazing Management – Rotational grazing and avoiding high-risk pastures can reduce internal parasite exposure and slow resistance without relying solely on pharmaceuticals.
-
Monitoring Parasite Loads – Fecal egg counts and veterinary diagnostics guide treatment decisions and help maintain drug efficacy.
-
Targeted Deworming – Treating based on need, not habit, protects product longevity and slows the spread of resistance.
Practical Tips from the Field
Dr. Matejka shared eight simple but critical steps that help producers get the most from parasite treatments:
-
Dose accurately based on weight.
-
Avoid applying to wet or manure-covered hair.
-
Treat only when parasites are present.
-
Rotate insecticides across drug classes when possible.
-
Prevent overstocking and overgrazing.
-
Quarantine new animals and test before entry.
-
Use rotational grazing to reduce parasite exposure.
-
Cull persistently unthrifty, high-shedding animals.
These practical habits can significantly improve treatment results and slow the development of resistance within herds.
Looking Ahead
Both experts emphasized that parasite management isn’t about eliminating every worm, but maintaining balance. Leaving a portion of untreated animals (known as refugia) helps sustain a population of susceptible parasites, which slows resistance.
As herds head into the fall and winter months, producers are encouraged to rethink routine parasite control programs. A more precise, data-driven approach not only safeguards herd health but also protects the long-term efficacy of deworming products.
The full BCRC webinar, The Ins and Outs of Parasite Management, offers an in-depth discussion on emerging resistance, testing protocols, and practical treatment strategies.
🎥 Watch the Full Webinar
The Ins and Outs of Parasite Management
Hosted by the Beef Cattle Research Council (March 2025)
(Video courtesy of the Beef Cattle Research Council. View more resources and upcoming events on BCRC’s website.)
Editorial Note
This article provides an overview of insights shared during the Beef Cattle Research Council webinar “The Ins and Outs of Parasite Management,” featuring Dr. John Gilleard (University of Calgary) and Dr. Carling Matejka (Veterinary Agri-Health Services). Information has been summarized and contextualized for BeefWeb readers.
