Sensory neuropathy (SN) is a severe neurological disease caused by the degeneration of sensory and, to a lesser extent, motor nerve cells. The onset of the disease in affected Border Collies is from 2 to 7 months of age and signs include knuckling of the feet, self-mutilation wounds (caused by excessive chewing or licking due to the lack of feeling in the limbs) and a progressive incoordination of gait (ataxia). A progressive loss of sensation occurs in all limbs. Urinary incontinence and regurgitation can occur in the later stages of the disease. Prognosis is poor, with no effective treatment available. As quality of life is severely affected, dogs with SN are euthanized on welfare grounds usually before two years of age.
Carriers can still be bred to clear dogs. On average, 50% of such a litter will be clear and 50% carriers; there can be no affected dogs produced from such a mating. Pups which will be used for breeding can themselves be DNA tested to determine whether they are clear or carrier of SN.