Trapped Neutrophil Syndrome in Border Collies: Causes & Testing

Trapped neutrophil syndrome (TNS) is a fatal inherited immune disorder primarily seen in Border Collies. This condition arises when the bone marrow produces neutrophils—white blood cells crucial for combating infections—but a genetic mutation prevents their release into the bloodstream. As a result, the immune system is left severely weakened, increasing susceptibility to infections.

TNS causes severe neutropenia, meaning dogs affected have dangerously low levels of neutrophils. Symptoms typically appear in puppies between 6 and 12 weeks of age. Sadly, most affected puppies survive only a few months, though milder forms can manifest symptoms later in life.

Understanding Trapped Neutrophil Syndrome: Causes and Symptoms

This disorder stems from an autosomal recessive mutation in the VPS13B gene. This genetic fault traps neutrophils within the bone marrow, preventing them from entering circulation and providing essential immune defense.

Common clinical signs include poor growth, lethargy, ongoing infections affecting the respiratory tract, skin, eyes, and ears, as well as diarrhea and vomiting. Physically, affected puppies may be smaller compared to their littermates and exhibit a narrow, elongated skull often described as ferret-like. Some may experience swollen joints, lameness, or painful inflammation known as hypertrophic osteodystrophy.

Which Dogs Are Affected?

TNS is breed-specific, with Border Collies at the highest risk. Approximately 7% of Border Collies in the USA carry this gene mutation. Therefore, breeders committed to maintaining breed health must carefully test potential breeding pairs to avoid passing this condition to puppies.

Inheritance of TNS: Genetics Explained

The syndrome follows an autosomal recessive inheritance pattern. Dogs fall into three genetic categories:

• Clear – they have no mutation and cannot pass TNS to offspring.
• Carrier – they carry one copy of the mutation but do not exhibit symptoms.
• Affected – they carry two copies of the mutation and develop clinical signs.

Breeding decisions involving these categories directly influence the risk of producing affected pups. Genetic testing is essential for breeders to prevent mating two carriers, reducing the risk of affected puppies.

Testing Your Border Collie for Trapped Neutrophil Syndrome

If you own or plan to breed a Border Collie, testing is critical. A veterinarian can collect a DNA sample, typically through a cheek swab or blood draw, which is submitted to an accredited laboratory authorized to conduct TNS testing in the US. Test results will indicate whether your dog is clear, a carrier, or affected.

In the United States, labs approved by organizations such as the AKC Canine Health Foundation often perform this testing, helping breeders make informed, responsible breeding choices.

The Importance of Responsible Breeding

Currently, no cure exists for trapped neutrophil syndrome, and affected puppies rarely survive beyond a few months. The best approach to managing TNS is prevention through informed breeding. Dedicated breeders routinely test their dogs, avoid breeding two carriers together, and strive to reduce the mutation’s prevalence within the Border Collie population.

For prospective Border Collie owners, ask breeders about genetic health screening and test results before getting a puppy. Choosing a healthy pup from responsible breeders safeguards not only your pet's life but also the breed’s future vitality.

Summary and What to Do Next

Trapped neutrophil syndrome is a serious genetic disorder affecting Border Collies, resulting in compromised immunity and early death. Learning about the symptoms, inheritance patterns, and testing can empower breeders and owners with the knowledge to protect the breed's future.

If you have or want a Border Collie, discuss TNS testing with your veterinarian and select reputable breeders who conduct proper health screening to help ensure the well-being of your new pet.