Trapped Neutrophil Syndrome (TNS) in Border collies

Trapped neutrophil syndrome is a hereditary health condition in which the affected dog’s bone marrow produces the necessary neutrophils (white cells) required for a healthy immune system, but cannot release them into the dog’s bloodstream, where they are used to fight off illness.

Ultimately, the condition’s effect on the immune system usually proves fatal, because a minor illness or infection cannot be fought off by the body in the normal way.

Previously, the condition generally went undiagnosed in most cases, or was written off as fading puppy syndrome. Affected dogs rarely live past their first year, and sometimes only make it to a few months old.

Because trapped neutrophil syndrome is a hereditary health condition, it cannot be caught or transferred from dog to dog other than by means of inheritance, and because the condition cannot be cured or prevented, people who are considering dogs that are classed as at risk of inheriting the condition should be tested prior to breeding. This allows potential breeders to make an informed decision about the viability of any given match.

In this article, we will look at trapped neutrophil syndrome in dogs in more detail, including what sort of dogs can be affected by the condition, how the heredity of the condition works, and how to get your dog tested. Read on to learn more.

More about trapped neutrophil syndrome

Trapped neutrophil syndrome (TNA) is caused by a mutation in the of the VPS12B protein sorting gene, which causes the white cells that the dog’s bone marrow naturally produces to become trapped in the bone marrow, unable to be released into the bloodstream where they are required to form an important part of the dog’s immune system.

This means that a dog born with the condition will be unable to fight off infections and illnesses, as their immune system does not form properly. Puppies are often smaller than other littermates who are unaffected by the condition, and some affected puppies will also be born with an unusual appearance with a particularly long, slim skull and legs.

Puppies born with the condition may begin to develop infections as a result from just a few weeks old, but in some cases it may not become apparent until the dog is over a year old.

What sort of dogs can be affected by the condition?

Trapped neutrophil syndrome is a hereditary disorder, which means that once it appears in the gene pool for any given breed of dog, it can potentially spread widely across the breed as a whole due to the fact that pedigree dogs are all bred from the same wider breed gene pool.

The Border collie dog breed is the breed considered to be at the highest risk of passing the condition on, and the gene mutation that causes trapped neutrophil syndrome is found in between 7-% of all Border collies, which is quite a significant demographic of the available gene pool.

Generally, dogs that have inherited the affected form of trapped neutrophil syndrome will become ill as a result of the condition before they reach their first birthday, sometimes within just a few weeks of birth. It is highly unusual for the condition to present for the first time in dogs older than two.

How does the heredity of the condition work?

Trapped neutrophil syndrome is an autosomal recessive condition, which means that different combinations of gene heredity lead to different end results in puppies. Dogs can have one of three statuses of trapped neutrophil syndrome: clear, carrier or affected.

Clear dogs do not carry any form of the gene mutation that causes the condition, while carrier dogs are not affected by the condition themselves, but can pass it onto their offspring. Affected dogs are those that are suffering from the condition themselves.

A simple outline of the inheritance pattern of the condition is as follows:

• Two clear dogs will produce clear puppies.
• Two affected dogs will produce affected puppies.
• Two carriers will produce a litter with mixed odds for each puppy-50% chance of carrier status, 25% chance of clear status, and 25% chance of affected status.
• A clear dog and a carrier will produce 50:50 clear and carrier dogs.
• A clear dog and an affected dog will produce a litter of carriers.
• A carrier and an affected dog will produce 50:50 affected and carrier dogs.

How can you get your dog tested?

If you own a Border collie that you are considering breeding from, it is really important to find out your dog’s status (and that of the other potential parent dog too) before making a firm decision, in order to ensure that the match produces healthy puppies.

This means asking your vet to take a DNA sample from your dog, which is then sent off to one of The Kennel Club’s approved laboratories for testing. Your dog’s status (clear, carrier or affected) will then be returned to you.