Silent Profit Thieves: Managing External Parasites

When we discuss parasites in cattle, the internal species are typically the first that come to mind. However, external parasites–including but not limited to lice, mites and ticks– can also cause significant animal discomfort and erode your profit margin.

External parasites largely cause issues by impacting animal grazing behavior, increasing stress and, most importantly, transmitting several serious diseases, as noted in a recent Beef Cattle Research Council (BCRC) webinar, The Ins and Outs of Parasite Management, which featured Drs. John Gilleard of the University of Calgary and Carling Matejka of Veterinary Agri-Health Services.

How much is it costing you?

According to Matejka, the economic losses from parasites (both internal and external) are estimated at $8.5 billion annually or $190 per head in the U.S. The top three parasites are any of the gastrointestinal group, ticks and live flukes. Other lesser but no doubt important external parasites include lice, mosquitos, cattle grubs and mites.

As she puts it, parasites are “silent profit thieves.” They impair immune function, decrease reproduction through lower conception rates, and reduce feed efficiency, which impacts live weight and carcass yield, decreases carcass grades and leads to greater greenhouse gas emissions.

Common parasites, like flies, can transmit pink eye and ticks can cause tick paralysis or blood diseases, including anaplasmosis and babesiosis. These insects are powerful vectors that can carry contagions across borders and different operations. For a recent example of this significance, look cattle fever ticks in Texas cited by the Animal and Plant Health Inspection Service as “the most dangerous cattle ectoparasites in the United States.” This has led to careful protocols and regional quarantine procedures to prevent the spread.

Cattle of all age ranges can be impacted by external parasites, but we usually see the impact during the growing stages when weight gain is impacted according to Drs. Kateryn Rochon from the University of Manitoba and Shaun Dergousoff from Agriculture and Agri-Food Canada in their BCRC article Parasites-External. Additional impacts such as dams with decreased milk production, a higher disease transmission, anemia and/or damaged hide or meat can also be measured.

“The life cycle of each pest determines when they are active throughout the year. The timing of adult activity overlaps for several types of pests, so producers should be aware of what pests are present in their region. The timing of pest activity can vary throughout the day ,” write coauthors Rochon and Dergousoff.

Because understanding lifecycles are so crucial in good parasite management, there should be a well-grounded familiarity into what these look like for specific regions and how seasonal abnormalities can author them. A lot of extension services have excellent visual materials for the reference of you and your team.

Symptoms and Treatments

Common signs associated with external parasites are often quite obvious and include itching, hair loss, overall stress, changes in grazing behavior, and production losses. Before beginning any treatment, it’s essential to confirm that parasites are indeed the cause—many factors can lead to symptoms like hair loss or weight loss, and close-up visual inspection is often required for proper verification.

Dr. Gilleard emphasized that, as with internal parasites, the goal with external parasites should not be complete elimination but sustainable management. He pointed out that the industry currently takes a “treat-first” approach to parasite control, when instead, producers should adopt an “assess-first” mindset. Integrated pest management, or IPM, is one strategy that supports this shift. It combines preventative measures to keep parasite populations below economically damaging levels and uses targeted treatments only when needed.

IPM strategies encourage producers to accurately identify the pest species, understand its life cycle, and assess the severity of the problem before selecting control options. This might include monitoring animal behavior, using traps, visually inspecting livestock, or surveying pastures and barns for breeding grounds. Recordkeeping is also key. Maintaining detailed logs of product use by year and season can help evaluate what’s worked in the past and guide future treatment choices.

Matejka outlined several recommended steps for managing infestations—ideally in consultation with a qualified veterinarian.
●Identify the Pest: Accurate identification is critical for selecting the most effective treatment.
●Develop a Treatment Plan: Tailor strategies to the specific pest and infestation level.
●Implement Treatment: Rotate insecticide classes annually to reduce resistance risk and apply follow-up treatments as necessary.
●Reduce Risk Factors: Avoid overcrowding, manage manure and water carefully, and implement fly control in barns or other structures.
●Evaluate Treatment Effectiveness: Monitor results and adjust as needed to ensure long-term control.

Ultimately, successful external parasite control comes down to good assessment, strategic planning, and long-term monitoring, rather than aiming for complete eradication. IPM helps producers make thoughtful, sustainable decisions that protect animal health and farm
profitability.

By Jaclyn Krymowski for American Cattlemen.

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