Collies and Shetland Sheepdogs (Shelties) have specific health considerations, particularly regarding heartworm prevention and a genetic mutation known as MDR1 sensitivity. Understanding these issues is crucial for ensuring the well-being of these beloved breeds. This guide focuses on safe heartworm prevention and explains why certain common medications can be dangerous for Collies and Shelties.
Understanding Heartworm and Safe Prevention
Heartworm disease is a serious and potentially fatal condition caused by parasitic worms transmitted through mosquito bites. The American Heartworm Society provides comprehensive information on the causes and geographic distribution of heartworm. For Collies and Shelties, selecting the correct heartworm preventative is paramount.
Interceptor is the only heartworm prevention medication recommended as safe for Collies, Collie-mixes, Shelties, and Sheltie-mixes. This is because Interceptor does not contain ivermectin, a common drug in other heartworm preventatives that can have deadly effects on these breeds. Heartworm prevention is straightforward: administer one Interceptor tablet monthly. Consult your veterinarian to determine if year-round prevention or a seasonal approach (typically April to November) is best for your area, as many vets now recommend 12-month administration.
Why “No Heartguard” for Collies and Shelties
Heartgard, another popular heartworm medication, does contain ivermectin. Under no circumstances should a Collie or Sheltie be given Heartgard. A significant percentage of Collies, estimated between 30-50 percent, can experience a deadly reaction to ivermectin. This adverse reaction occurs because susceptible Collies cannot metabolize ivermectin effectively, leading to toxic levels accumulating in the brain. For Shelties, who may already be prone to epilepsy, seizures have been reported after taking Heartgard. This risk has led to the common veterinary adage: “White feet, don’t treat.”
The Science Behind MDR1 Sensitivity
In 2001, Dr. Katrina Mealey at Washington State University’s College of Veterinary Medicine identified that drug sensitivities in certain breeds stem from a mutation in the multi-drug resistance gene (MDR1). This gene is responsible for producing P-glycoprotein, a protein that helps pump many drugs and toxins out of the brain.
Approximately three out of every four Collies possess the mutant MDR1 gene, and this mutation has also been identified in Shelties. The presence of the mutant MDR1 gene makes specific medications extremely dangerous for these dogs. Dogs with this mutation struggle to eliminate certain drugs from their brains as effectively as dogs without the mutation. This can lead to abnormal neurological signs, potentially resulting in severe illness requiring extensive veterinary care or even death.
Other breeds identified with the mutant MDR1 gene include Australian Shepherds, Old English Sheepdogs, English Shepherds, German Shepherds, Long-Haired Whippets, Silken Windhounds, and various mixed-breed dogs. The only definitive way to determine if an individual dog carries the mutant MDR1 gene is through genetic testing. As more dogs are tested, the list of affected breeds is likely to expand.
Obtaining Interceptor and Avoiding Loperamide
If your veterinarian does not have Interceptor readily available, request a prescription to order it online. If your vet is hesitant to prescribe Interceptor for your Collie or Sheltie, it is advisable to seek a second opinion, as your dog’s life could be at risk. If your vet is open to further information, refer them to the resources and links provided.
Furthermore, some veterinarians may prescribe anti-diarrheal medications like Imodium, which contains loperamide. However, due to their MDR1 sensitivity, Collies and Shelties should never be given Imodium or any medication containing loperamide.
Further Resources on MDR1-Related Drug Sensitivities
For in-depth information on the MDR1 mutation from Washington State University’s College of Veterinary Medicine, you can consult their Veterinary Clinical Pharmacology Lab’s resources on Multidrug Sensitivity in Dogs. The university also offers drug sensitivity testing for individual dogs. For complete details and instructions on how to get your dog tested, please visit WSU’s MDR1 Testing for Dogs and Cats webpage.
It is important to be aware that several other drugs can be dangerous to Collies, Shelties, and other breeds carrying the MDR genetic mutation. Studies indicate that a significant 75 percent of Collies carry this mutation and are therefore at risk. This underscores why medications like Heartgard pose a serious health concern. Refer to the University’s Veterinary Clinical Pharmacology Lab’s Problem Medications for Dogs list for a comprehensive overview.
Caution: While the formula for Heartgard was reportedly changed and relabeled as “now safe for Shelties and Collies” several years ago, dogs at risk can still experience adverse reactions. Always prioritize safe, veterinarian-approved medications for your Collie or Sheltie.
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