Breeds Arrising from the Collie as Indicated by a Pharmacogenetic Mutation

(My first dog and best friend, a Collie.)

     Today there are a host of techniques available to help unravel the history of the dog.  Some discoveries appear in the most unexpected places.  One such happened when the antiparasitic drug ivermectin was introduced to the public.  Ivermectin kills by causing paralysis to occur in some nematodes and arthropods.  When first developed it was considered safe for use in canines because a mechanism in mammals keeps the drug from crossing the blood brain barrier.  However, it soon became evident that ivermectin is life threatening to some dogs, especially individuals of Collie lineage.

      A protein called P-glycoprotein plays an essential role in determining what is passed through the blood brain barrier in mammals.  An allele mutation, mdr1-1, results in dysfunction in the P-glycoprotein which allows a number of drugs including Ivermectin to cross the blood brain barrier resulting in the animal experiencing a toxic reaction.  A study was conducted to determine if other breeds beside the Collie are affected by the mdr1-1  mutation.

         The researchers tested four groups of dogs, 1) breeds related to Collies, 2) European herding breeds, 3) Sight hounds and other breeds which exhibited sensitivity to the above mentioned drugs, including ivermectin, and 4) 90 unrelated breeds.  The results indicated that seven herding breeds including both US and UK Collies, Australian Shepherds (including Miniatures,) Old English Sheepdogs, English Shepherds, McNabs, Shetland Sheepdogs and two sight hounds (the Long haired Whippet and the Silken Windhound) carried the mutation.  It appears that the geographic origin for mdr1-1 is Great Britain as no mutation occurred in Continental European breeds.

     It is surmised that the mutation was passed to working collie type breeds before the introduction of sheepdog registries.  How it also entered the sight hound gene pool is conjecture; however, the re-creator of the Longhaired Whippet (1950s) also bred Shetland Sheepdogs.  The Silken Windhound was bred in the 1980s and is a cross of several breeds including Longhaired Whippets. [1]

      What can we learn about the history of dogs from this study?   The idea of the purebred dog is really a nomenclature.  In reality it means very little.  A pug may seem to have little in common with an Irish Wolfhound but the truth is they are really identical twins wearing differing raiment.  Where it counts, at the genetic level a dog is a dog is a dog.  Even dogs which differ in behaviors, a sight hound vs. a herding breed for example, are linked because they all share a common ancestry.  The most “ancient” of the breeds such as the Basenji are distinct because they lived in geographic isolation.  The vast majority of today’s purebred dogs have only existed in breeder induced isolation for a few short years.  Their ancestors interbred.  This becomes all too apparent when a mutation such as mdr1-1 crops up.

Endnote:  For naturopaths and all natural breeders, it is no surprise that employing synthetic chemical and drugs is problematic.  Their benefits should always be weighed carefully against the potential for life threatening side effects.

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[1]K. Broman, K. Mealey, M. Neff, N. Pedersen, K. Robertson, N. Safra, M. Slatkin, A. Wong, “Breed Distribution and History of Canine mdr1-1 , a Pharmacogenetic Mutation that Marks the Emergence of Breeds from the Collie Lineage,” www.pnas.org, accessed August 30, 2012.