Trapped Neutrophil Syndrome (TNS)

Description

Trapped Neutrophil Syndrome (TNS) is an autosomal recessive mutation affecting Border Collies. Autosomal recessive genetic mutations are mutations that can be passed from either parent and require two copies of the gene to show symptoms. TNS was discovered in 1996, in Australia and New Zealand. The mutation causes the dog's infection-fighting white blood cells to be "trapped" and not released from the bone marrow. Without sufficient white blood cells in the bloodstream, the dog's immune system is unable to fight off infections and the dog eventually dies, usually when they are a few months old.

An affected puppy may not show any specific symptoms, other than susceptibility to infection. They may be smaller and less healthy than unaffected puppies. Occasionally, a dog will not show symptoms until they are older, around 7 months old. There is currently no treatment for TNS. However, the infections can be treated with antibiotics or steroids to prolong the life of the dog. 

Carriers of the mutation (dogs that carry one copy of the mutation) will not show any symptoms but will pass the mutation on to a percentage of their offspring. It is estimated that about 10% of Border Collies are carriers of the mutation, so testing for TNS before breeding is advisable. If two carriers are bred to one another, there is a 25% chance per puppy that they will develop symptoms.