New study reveals gaps in bison parasite management

Gastrointestinal parasites pose significant health risks to North American bison, but overuse of deworming drugs can lead to reduced effectiveness and the development of drug-resistant parasites. A new study by Texas A&M researchers published in Veterinary Parasitology sheds light on how bison producers manage parasites, offering insights that could help develop targeted deworming strategies and preserve the limited drugs available to producers.

Gastrointestinal nematodes, commonly known as gastrointestinal worms, are a major concern for bison, causing issues like diarrhea, poor weight gain, and reduced production. In severe cases, these parasites can even contribute to bison deaths. However, researchers note that simply deworming more frequently is not the solution. Most previous research on bison has focused on larger herds in northern states and Canada, leaving a knowledge gap regarding operations in the southern U.S. Surveying bison producers, the study found that nearly 90% dewormed their animals at least once annually, while about one-third did so more frequently.

Yet, diagnostic tools to determine if treatment is necessary were rarely used. Producers often adapt practices from the cattle industry, using medicated feed to administer dewormers and adapting treatments developed for other ruminants, despite limited information on optimal bison-specific deworming practices. The researchers are particularly concerned about anthelmintic resistance, where parasites develop resistance to dewormers through repeated exposure.

This resistance process is similar to antibiotic resistance, with susceptible parasites being killed while resistant ones survive and reproduce. To combat this, diagnostic testing can help producers make more targeted treatment decisions, reducing drug use and pressure on parasite populations to develop resistance. Introducing refugia, or maintaining untreated parasite populations, can also help slow the spread of resistance, though fewer than 10% of surveyed producers currently implement this strategy.

Researchers emphasize the need to consider long-term impacts when implementing deworming practices, rather than focusing solely on immediate production goals.