Imerslund-Grasbeck syndrome in Border Collies: Genetic Guide

Imerslund-Grasbeck syndrome (IGS) is an inherited health condition primarily affecting Border Collies puppies, with genetic markers found in about 7-8% of this breed worldwide. This autosomal recessive disorder leads to a failure to absorb vitamin B12 (cobalamin) properly, causing anaemia and other health complications. Responsible breeders use genetic testing to reduce the spread of this condition within the breed.

Understanding Imerslund-Grasbeck Syndrome

IGS is caused by a mutation in the CUBN gene, essential for absorbing vitamin B12 in the intestine. Without proper absorption, dogs develop symptoms often from a young age, although some Border Collies may show signs later in life. Clinical signs include poor weight gain, lethargy, seizures, vomiting, diarrhoea, anaemia, and proteinuria (protein in the urine) despite normal kidney function.

How IGS Affects Dogs

Vitamin B12 deficiency impairs red blood cell production, leading to non-regenerative anaemia—a serious condition where the body cannot replenish blood cells. Affected puppies may show neutropenia (low white blood cell count), appetite loss, frequent urination, and failure to thrive. Early detection can significantly improve the dog's quality of life.

Inheritance and Genetic Status

IGS in Border Collies is an autosomal recessive condition, meaning a pup must inherit two copies of the mutated gene (one from each parent) to be affected. Dogs are classified as:

• Clear: Free from the mutation and cannot pass it on.
• Carrier: Have one mutated gene but do not show symptoms; can pass the mutation to offspring.
• Affected: Have two copies of the mutated gene and show symptoms.

The possible combinations from breeding pairs are:

• Two clear dogs produce clear puppies.
• Two carriers have a 25% chance of affected puppies, 50% carriers, and 25% clear.
• A clear and carrier pair produce 50% carriers and 50% clear puppies.
• An affected and clear dog produce 100% carriers.
• An affected and carrier pair produce 50% affected and 50% carriers.
• Two affected dogs produce affected puppies only.

Testing Your Dog for IGS

Knowing your dog's genetic status is crucial for responsible breeding and health management. DNA testing can be performed via blood samples, cheek swabs, or dew claw clippings. The Kennel Club has approved laboratories to provide reliable test results, assisting breeders in making informed decisions and avoiding producing affected puppies.

Treatment and Care for Affected Dogs

While there is no cure, lifelong injections of vitamin B12 bypass the gut absorption problem and can manage symptoms effectively. Regular veterinary care and monitoring help affected dogs maintain good health and quality of life.

The Importance of Responsible Breeding

To reduce the incidence of IGS, breeders should avoid mating two carriers or affected dogs. Using genetic testing results helps maintain healthy breeding lines, improving the general welfare of the Border Collie breed globally. Prospective owners should seek reputable Border Collie breeders who test for genetic conditions like IGS and prioritise the health of their puppies.

Summary

Imerslund-Grasbeck syndrome is a serious but manageable condition in Border Collies caused by a specific genetic mutation affecting vitamin B12 absorption. Early diagnosis through genetic testing and responsible breeding decisions are vital. Affected dogs benefit from lifelong vitamin B12 supplementation, and informed breeders play a key role in reducing this condition's impact on future generations.