What is MDR1? - Multiple Drug Sensitivity
Sensitivity to certain classes of drugs, notably the parasiticide ivermectin, as well as certain gastroprotection and anti-cancer medications, occurs in dogs with a mutation in the ABCB1 gene.
In the realm of veterinary medicine, the prevalence of genetic mutations in certain dog breeds often presents both challenges and opportunities for effective healthcare. Among the noteworthy genetic variations affecting canines, the Multidrug Resistance mutation in the ABCB1 gene has garnered significant attention, particularly in herding breeds such as Australian Shepherds, Collies, and Border Collies. Despite the widespread belief associated with the adage "White feet don't treat," indicating a likelihood of this mutation in dogs with white markings on their feet, the reality is far more complex and widespread.
The ABCB1 mutation, located on chromosome 14, is a genetic anomaly that impacts the functionality of a protein responsible for pumping certain drugs out of cells, limiting their effectiveness. Dogs possessing this mutation might exhibit adverse reactions or sensitivity to a variety of medications, including commonly prescribed drugs such as ivermectin, loperamide, and certain chemotherapy agents.
Initially thought to be primarily prevalent in dog breeds with white feet or white markings, recent advancements in veterinary genetics have revealed a broader landscape. While herding breeds remain particularly affected, it's essential to recognize that the mutation isn't confined solely to them. Many other breeds and mixed-breed dogs also carry the ABCB1 mutation, highlighting the necessity of widespread awareness and proactive measures in veterinary care.
The oversimplification of associating the mutation exclusively with specific physical markings on a dog's feet has led to misconceptions and potential oversight in diagnosing or administering appropriate treatments. Veterinarians and dog owners alike must understand that the mutation's presence isn't always visibly linked to white patches on a dog's extremities. The complexities of genetic inheritance and variability demand a more comprehensive approach to identifying dogs at risk and providing them with safe and tailored treatment regimens.
The emerging field of genetic testing for dogs has played a pivotal role in identifying and managing this mutation. With advancements in technology, DNA testing has become an invaluable tool in preemptively determining a dog's susceptibility to the ABCB1 mutation. Such tests allow veterinarians to make informed decisions about medication administration and dosage adjustments, ensuring the well-being of affected dogs and preventing adverse reactions to drugs.
Furthermore, spreading awareness among dog owners about the prevalence of the ABCB1 mutation in various breeds and mixed dogs is vital. This knowledge empowers them to take proactive steps, such as genetic testing, when considering medications for their pets, even if they do not belong to the traditionally associated high-risk breeds.
In conclusion, the Multidrug Resistance mutation in the ABCB1 gene represents a noteworthy challenge in veterinary medicine. While historically linked with specific herding breeds and the belief encapsulated in the "White feet don't treat" adage, it's essential to recognize the mutation's broader presence across various dog breeds and mixed lineages. Embracing genetic testing and wider education in veterinary practice is pivotal to ensuring the well-being and appropriate medical care for our beloved canine companions, regardless of their breed or physical markings.
Signs & Symptoms in Affected Dogs
Onset in Young Adulthood: Symptoms often appear when a dog is initially exposed to problem drugs like high-dose ivermectin or acepromazine.
When Symptoms Develop
Post-Exposure: After being administered an MDR1 problem drug, symptoms can vary from vomiting and diarrhea to more severe issues like lethargy, seizures, or even coma.
Diagnosis by Veterinarians
Retroactive Diagnosis: Usually identified after an adverse reaction to a problem drug. However, preemptive genetic testing can help prevent initial adverse reactions.
Treatment of the Condition
Avoidance: MDR1 can be completely avoided by steering clear of problem drugs or their problematic dosages.
Actions for Affected Dogs
Consult the MDR1 Problem Drug List: Refer to resources such as the Washington State University list. Inform your vet to note this in your dog's file for future reference.
Management Strategies for Farm Dogs: For farm dogs with MDR1, consider keeping them away from herds where ivermectin is regularly used as an antiparasitic, or opt for alternative antiparasitic measures in their working areas.