July 2009

Small Strongyles Gain Strength: Moxidectin May Be Failing, Too

In our October 2008 issue, we told you about studies that had found small strongyle fecal egg counts can become positive again in as short a period as 30 days after ivermectin treatment. This likely represents the emergence of strains with ultra-short life cycles that will flourish on the more traditional eight-week deworming timing.

Now a study from Auburn University has found the same is true for moxidectin (Quest). A herd of draft horses that had been routinely dewormed with moxidectin for five years was checked for eggs at 0, 7, 30, 60 and 90 days after deworming. Egg counts were reduced at 7 and 30 days, but not 60…