Why Are Many Border Collies Sensitive to Ivermectin?

The Border collie is a highly intelligent working herding dog breed, known as one of the smartest dog breeds worldwide. They remain popular both as working farm dogs and as active companions in canine sports like flyball, agility, and obedience due to their incredible ability to learn and perform complex commands.

Border collies require significant physical exercise and mental stimulation, which can sometimes be underestimated by first-time owners. Their energy and intelligence make them a fulfilling pet choice for owners prepared to meet these demands.

What Is Ivermectin and How Does It Work?

Ivermectin is a widely used antiparasitic and anthelmintic agent employed in various animals, including livestock, horses, birds, small mammals, and dogs, primarily to control worm infestations. It acts at the cellular level by increasing chloride ions in parasites' cells, leading to their death.

For most animals, ivermectin is safe because their receptor cells do not allow toxic levels into sensitive areas like the brain, thanks to a protective membrane called the blood-brain barrier.

In dogs, this blood-brain barrier usually prevents ivermectin from reaching brain cells. However, in some dogs, this barrier is faulty due to a genetic mutation, causing sensitivity and potentially severe reactions to ivermectin.

Why Are Many Border Collies Sensitive to Ivermectin?

A significant proportion of Border collies carry a mutation in the MDR1 gene, which affects the production of P-glycoprotein. This protein helps to pump certain toxins, including ivermectin, out of the brain, maintaining the blood-brain barrier’s integrity.

When the MDR1 gene is mutated, the blood-brain barrier becomes compromised. This allows ivermectin to cross into the brain in toxic amounts, potentially inducing severe neurological symptoms. Approximately 75% of Border collies, including mixed breeds with Border collie heritage, may carry this mutation.

Because of this, ivermectin and some related drug treatments should be avoided or used with extreme caution in Border collies and working herding breeds with Border collie ancestry. Your vet will understand this and recommend safe alternatives for controlling parasites.

Recognising and Managing Ivermectin Sensitivity

If a Border collie with the MDR1 gene mutation is exposed to ivermectin, they may show symptoms including:

• Difficulty standing or walking
• Unsteadiness or tremors
• Excessive sleepiness or lethargy
• Reduced responsiveness to stimuli
• Excessive drooling and vomiting
• Abnormally slow heart and breathing rates
• In severe cases, seizures or coma

Prompt veterinary intervention can often manage ivermectin toxicity, but it is critical to seek help immediately if exposure is suspected.

What Should UK Border Collie Owners Do?

Owners should always inform their vet if their dog is a Border collie or has Border collie ancestry. Never use over-the-counter ivermectin wormers without veterinary supervision. Genetic testing for the MDR1 gene mutation is available and highly recommended, especially if you plan to breed your dog or use medications that might pose risks.

Low doses of ivermectin, like those used in heartworm medications, are generally safe even for sensitive dogs, but the higher doses in other treatments should be avoided unless directed by a vet.

Can I Test My Border Collie for Ivermectin Sensitivity?

Yes, DNA testing for the MDR1 gene mutation is accessible through veterinary clinics or specialist laboratories. This test helps determine if your dog is:

• Homozygous for the mutation (very sensitive)
• Heterozygous (intermediate sensitivity)
• Clear (normal sensitivity)

Knowing your dog's status can guide safer medication choices and breeding decisions.

Summary and Responsible Ownership

Understanding the genetic susceptibility of many Border collies to ivermectin is vital in safeguarding their health. Responsible pet owners in the UK should work closely with their vets, rely on proper genetic testing, and ensure only safe, vet-approved medications are used for parasite control.

By staying informed and proactive, you can enjoy the many wonderful traits of this remarkable breed while keeping your Border collie safe from preventable drug reactions.