November 2003

Deworming Protocols Are In Jeopardy

The days of the simple

Horses turned out in crowded areas are more likely to need vigilant deworming.

It may be time to seriously rethink how we are deworming our horses. When we heard of ivermectin resistance being documented in cows (see August 2002), we warned that the same problem could occur in horses. It appears it has.

The Journal of the American Veterinary Medical Association reports the failure of ivermectin to eliminate roundworm infestation in 20 out of 37 foals treated with ivermectin. In some foals, the counts kept increasing between the time of treatment and a recheck 12 to 13 days later. …