The Parasite Puzzle: What a National Study Reveals About Goat Health, Resistance, and Smarter Deworming
For goat producers across the United States, few challenges are as persistent, costly, and frankly, as frustrating as gastrointestinal nematode (GIN) parasites. These microscopic foes are a leading cause of production loss, illness, and death in goats worldwide, silently impacting our animals’ well-being and our operations’ bottom lines. For too long, the primary line of defense has been anthelmintic drugs, those essential dewormers we rely on. Yet, a significant and alarming issue has emerged globally, including right here in the U.S.: widespread resistance to these very drugs. Imagine battling an invisible enemy only to find your most potent weapons are losing their edge; it’s a truly concerning scenario.
Recognizing this critical information gap, the U.S. Department of Agriculture (USDA) conducted the 2019 National Animal Health Monitoring System (NAHMS) study. This wasn’t just a small-scale regional survey; it was an ambitious undertaking designed to shed light on the current landscape of GIN infections and the control practices being employed by goat producers nationally. The study’s aims were clear: to quantify the parasite burden at both the individual animal and operation levels, to uncover any geographic patterns in GIN parasitism, and importantly, to identify risk factors that contribute to infection prevalence and intensity.
The scope of this study was impressive, encompassing 24 U.S. states. This broad coverage represented a substantial portion of the nation’s goat industry, specifically 80.4% of U.S. goats on operations with five or more goats and 75.8% of operations meeting the same size criteria. To gather the necessary data, researchers collected fecal samples from 9,879 goats across 623 different operations. Alongside these samples, detailed information was compiled through individual goat-level and operation-level questionnaires, providing a rich dataset for analysis. On average, about 15.9 goats were sampled per operation, with a range from 3 to 26 goats.
What did this comprehensive effort reveal? The estimated average fecal egg count (FEC) was remarkably consistent, with 658 eggs per gram (EPG) at the operation level and 651 EPG for individual goats. Perhaps one of the most striking findings, and a real game-changer for how we think about parasite control, was the observation that GIN burdens are over-dispersed. This means that a relatively small percentage of animals carry the vast majority of the parasite load. Specifically, the study found that a mere 24.1% of all tested goats were responsible for contributing a whopping 80% of the total FEC. Averaging this contribution across all sampled operations, approximately one-third of the sampled goats on operations were found to contribute to this significant parasite shedding. This insight alone challenges the old “treat every goat” mentality. Just don’t do it.
Geographic patterns also emerged from the data. Lungworm prevalence, for instance, was significantly lower in the Southwest region compared to the Northeast, Northwest, and Southeast. When looking at GIN FEC values, the highest operation-level counts were concentrated in the Northeast and Southeast regions. For individual animals, the highest FECs were found in the Southeast by univariate analysis, and in both the Northeast and Southeast regions when analyzed with multiple regression. These regional distinctions highlight that a one-size-fits-all approach to parasite control might not be the most effective strategy.
The study also meticulously identified numerous factors impacting mean FEC. Univariate analysis, which looks at one factor at a time, showed that primary operation production type (e.g., meat, dairy), primary land or facility management type, primary grazing or browsing management, the use of FAMACHA cards, body condition categorization, and the month of sample collection all significantly influenced FEC at both the operation and animal levels. At the individual animal level, U.S. regionality, goat type, breed, FAMACHA score, and browsing schedule were also found to be significant. Delving deeper with multiple regression analysis, which considers multiple factors simultaneously, researchers identified that deworming frequency in the previous 12 months, pasture housing practices, and the interaction between region and sample collection date were significant factors impacting mean FEC at the operation level. At the animal level, goat type, FAMACHA score, body condition categorization, primary grazing/browsing management, primary operation production type, and the interactions between region and both multiple species grazing and sample collection date, were significant. This wealth of data provides actionable insights for producers.
In essence, this study represents a vital update to our understanding of GIN parasitism in U.S. goats. It’s the first national report since the 2009 NAHMS Goat Study to comprehensively detail producer parasite control strategies and report GIN parasite egg shedding patterns across the country. By allowing for regional assessments, it offers a more nuanced understanding of the unique challenges facing producers in different parts of the U.S., offering a guiding light for future research and the development of regionally specific control practices.
Limitations
The article is comprehensive in its findings and methodology, but it does not include a dedicated section discussing its limitations directly. While the study covered a significant portion of the U.S. goat population and operations (80.4% of goats on operations with ≥5 goats and 75.8% of operations with ≥5 goats), it was conducted in 24 states. This means it didn’t cover every U.S. state, though it aimed to capture current GIN control strategies in as much of the U.S. as possible. Also, it’s a snapshot in time from 2019, albeit with samples collected across different months. While the findings provide valuable current data, the dynamic nature of parasite populations and management practices means that continued monitoring is always beneficial. Another point to consider is the reliance on producer-reported information for management practices, though this was complemented by direct fecal sample analysis.
Relevance for Us
The insights from this study are incredibly powerful:
- Embrace Targeted Selective Treatment (TST): About a quarter of goats contribute to 80% of the parasite burden. Treat the few, not the whole herd.
- Utilize FAMACHA Scoring and Body Condition: These practical tools help identify goats most affected by parasites.
- Re-evaluate Management: Grazing, housing, and deworming schedules can all impact parasite loads.
- Know Your Region: Tailor your parasite control plan to local conditions and climate patterns (not the advice Joe the Goat Owner in Alaska gives you on Facebook).
- Face Anthelmintic Resistance Head-On: Rotate drugs, use integrated methods, and protect the tools that still work.
Quick Takeaways
- A small percentage of goats carry the majority of parasites.
- FAMACHA scoring and condition scoring are practical, research-supported tools.
- Regional parasite pressures differ. Local solutions work best.
- Widespread dewormer resistance is already here in the U.S.
Article Citation
Urie, N. J., Branan, M. A., Wiedenheft, A. M., Dennis, E., Marshall, K. L., Burke, J. M., … & James, E. (2025). A national survey of the gastrointestinal nematode control practices used by goat producers in the United States. Veterinary Parasitology, 334, 110375. https://doi.org/10.1016/j.vetpar.2024.110375