What is MDR1 and is my dog effected?...
MDR1 is the abbreviated name of a gene called Multi-Drug Resistance 1. A mutation of this gene causes sensitivity to Ivermectin and a number of other drugs. Dogs with the mutation will react to those drugs.
Most herding type dogs including:- Australian Shepherd, Border collie, Collie, English shepherd, German Shepherd, Longhaired Whippet, McNab Shepherd (McNab Border Collie), Old English Sheepdog (Bobtail), Shetland Sheepdog (Sheltie), Silken Windhound, Rough Collie, Smooth Collie, Bobtail, American White Shepherd, Waeller (Wäller), Elo .
Ivermectin is commonly found in treatments for Heartworm.
If you’d like to read more about MDR1 and how it might effect your dog, here are a few resources you might find helpful: