Increasing importance of anthelmintic resistance in European livestock: creation and meta-analysis of an open database

The researchers performed a systematic review and meta-analysis of 197 publications representing 535 studies across 22 countries. They aggregated data on AR in GIN and F. hepatica, stratifying by host species and anthelmintic class. To address the limitations of previous studies, the authors used heuristic, sample-size weighted estimates of AR prevalence and developed composite indices to evaluate the relationship between observed resistance and research effort. They also conducted a SWOT analysis to identify systemic strengths, weaknesses, opportunities, and threats in current AR research.

• Widespread Resistance: AR is present throughout Europe. In sheep and goats, resistance is highest against benzimidazoles (BZ), while in cattle, resistance varies significantly by drug class.
• Temporal Trends: Longitudinal data indicate a clear trend of increasing resistance over time for all major anthelmintic classes in GIN. For instance, in the UK, resistance to BZ in sheep has risen significantly since 2010.
• Research Bias: There is a strong spatial bias in research, with Western Europe (particularly the UK) being heavily overrepresented compared to Eastern Europe. Furthermore, studies often focus on individual farms with suspected treatment failure, which likely inflates prevalence estimates.
• Management Success: The study highlights that in regions with established, long-term monitoring programs—such as Switzerland and Italy—the prevalence of AR remains lower, suggesting that sustainable parasite control practices can effectively slow the development of resistance.

The findings underscore that AR is a growing, continent-wide problem that requires urgent, coordinated action. By providing a baseline and a live database, this work serves as a critical tool for policymakers and industry stakeholders to advocate for sustainable control strategies, such as targeted selective treatment, and to shift research focus toward more robust, randomized surveillance methods.