Indiscriminate overuse of deworming products has led to increasing resistance among some parasite populations to their effects, and scientists warn that the chemicals currently available could eventually lose their effectiveness if such practices continue. Fortunately, research has also revealed that a much more targeted and conservative treatment approach—developed on a horse-by-horse basis—can protect the integrity of anthelmintic drugs while still keeping horses healthy. Implementing such a program requires a momentous shift in mindset as well as some preliminary investigative work to identify which horses need deworming (turns out not all of them do) and with what products. It's a big change but if we—as the entire horse keeping community—don't make it, the health of all our horses is at risk.
In early 2011, EQUUS worked with top parasitologists in the field to publish an in-depth Special Report on this topic. The report not only outlines the historical and scientific background of the resistance problem, but lays out in clear language how horse owners can change their deworming programs to address the issue. If you missed the report in EQUUS, here it is now as a PDF (click the link below) you can print out to refer to often, post at the barn or pass around to spread the word.