Canine leukocyte adhesion deficiency (CLAD) is an immunodeficiency disorder in dogs, caused by a defect of the white blood cells (leucoctyes). This defect means that the immune system cannot respond appropriately to infections. The disease is characterised by severe, recurrent bacterial infections. The first signs of CLAD DNA test at Canine Genetic Testing appear in puppies, around the age of 13 weeks. Signs include recurrent infections, fever, poor appetite, poor growth, impaired would healing and enlarged lymph nodes. Clinical signs progress and affected dogs generally die by the age of six months.
This form of the disease has been identified in Iris Setters, Irish Red and White Setters and cross breed dogs.
The single nucleotide substitution in the gene called ITGB2 that causes Canine leukocyte adhesion deficiency (CLAD) in Irish Setters is recessive. This means that dogs that carry two copies of the mutation (homozygotes) will almost certainly develop CLAD during their lives. Dogs that carry a single copy of the mutation (also known as carriers or heterozygotes) will not develop CLAD as a result of the ITGB2 mutation, but they will pass the mutation onto about half of any offspring they have. Breeding dogs that will not develop CLAD should be the breeder’s priority, with a reduction in mutation frequency within the whole breed being the secondary, longer-term target.
Carriers can be bred from safely, provided they are mated to a dog that has also been tested and is clear of the ITGB2 mutation (i.e. carry no copies of the mutation). If a carrier is mated to a clear dog approximately half of the resulting puppies will also be carriers, so should be tested themselves prior to breeding. Breeding carriers to tested, clear dogs is safe, in terms of avoiding dogs affected with CLAD, and will help to maintain the genetic diversity of a breed. It is therefore encouraged, particularly in the first few generations following the availability of a new genetic test, so that other desirable characteristics and traits can be preserved before the frequency of the disease mutation within the breed is gradually reduced.