CL and TNS Testing

CL is a devastating neurological disorder that results in rapid deterioration and early death in dogs. It is a hereditary disease in Border Collies that has been noted with growing numbers, especially in Australian populations. Breeders should educate themselves on this disease. Fortunately, there is now a DNA test available to expose genetic carriers, so all breeding stock suspected of being related to CL-affected lines should be tested prior to use.

Places where you can submit DNA samples to have your dog tested:

TNS (Trapped Neutrophil Syndrome) is a fatal genetic disease that strikes young puppies. It isn’t really a new disease but research into it – and the ability to identify carriers of the gene that causes it – has reached a new level. Dr. Alan Wilton of the University of New South Wales and the researcher who helped develop the test to find the gene responsible for causing CL has now turned his attention to this devastating disease.

TNS is an hereditary disease where the bone marrow produces neutrophils (white cells) but is unable to effectively release them into the bloodstream. Affected puppies have an impaired immune system and will eventually die from infections they cannot fight. Most affected puppies are euthanized on humane grounds.

Symptoms may be seen in puppies as young as 2 weeks or as old as 7 months of age. Affected puppies are usually smaller, have slower growth rates, and can appear to have a “ferret like” head and a poor hair coat. Some puppies are not obviously different until they become ill. Other symptoms of disease include lameness, lack of an appetite, diarrhea and a high temperature. Sometimes pups become ill after their first vaccination. TNS is a disease which ultimately causes a deficiency of the immune system, so symptoms can vary between pups.

Once thought to be rare, it is now believed that the disease goes undiagnosed for several reasons. First, not very many veterinarians (especially those here in the US) know about the disease to look for it. Second, even when looking, blood counts do not always show lower than normal neutrophil (white blood cell) counts. Finally, because it is an autoimmune-deficiency disease, young puppies present a variety of symptoms depending upon what infections they fall prone to. Thus many cases are not properly diagnosed and have just been thought to be “fading puppies”.

Making the diagnosis even more difficult is the fact that age of onset varies depending on which infection is involved at the time. Most puppies become ill before leaving the breeder but some do not have symptoms until later. The oldest known survivor was 2 years 8 months. Most affected puppies die or are euthanized by about 4 months of age.

TNS cases have been identified in New Zealand, Australia, United States and Great Britain. The most recent case positively diagnosed as TNS was born in the US, but the pedigree contained lines from the US, NZ, Australia and Great Britain. Research now suggests that the gene is widespread throughout the Border Collie breed. It is autosomal recessive, which means that both parents have to be carriers to produce an affected puppy. There is now a genetic test available to find carriers of the disease.

Page Updated 07/12/2016