Genetic Study of Ivermectin Sensitivity

In February 2004, the ICDCA was contacted by Dr. Katrina Mealey, a veterinarian on the faculty of Washington State University who asked for our assistance in conducting a genetic study involving Canaan Dogs.

The purpose of the study was to search for a mutation of the MDR1 gene discovered at Dr. Mealey's university which causes severe adverse reactions to Ivermectin (the active agent of Heartguard), other heartworm preventive or other medications such as antiparasitic drugs, chemotherapeutic drugs, or loperamide (Immodium®), digoxin, cyclosporin, and other drugs.

Dr. Mealey had already conducted similar studies with Collies, Australian Shepherds, and other breeds and found that at least 70% of Collies carry this mutation. Given the conjectured link between Canaan Dogs and Collies, it was natural to ask if our breed too carried the mutation.

As over the years there had been some reported possible adverse reactions to Heartguard in Canaan Dogs, and much discussion on this subject had occurred on the web, we were eager to help with this study. So we circulated an e-mail message to several of our members and breeders, selected to create a broad genetic representation, urging them to participate in the study and we also contacted several breeders abroad.

Many of them sent samples to Dr. Mealey' s laboratory for testing.

The results are now in: the mutation has not been found in any of the tested samples, neither in the USA nor abroad, and that included some of the dogs with possible adverse reactions to Heartguard We recently heard that UC Davis tested Canaans using archived samples and the results were also negative.

The size of these studies was not very large (25 dogs), so we can only conclude that if this mutation occurs in our breed after all, it must be fairly rare. This information should be useful to owners and veterinarians that have to compare the risk to their dogs presented by heartworms with the one, if any, presented by ivermectin.

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© 2005 Israel Canaan Dog Club of America, Inc.