Part of the official UK Kennel Club testing scheme in Bulldog, Dalmatian, Hungarian Vizsla (Wire-Haired), Large Munsterlander and Russian Black Terrier
The SLC2A9 gene codes for a protein that allows the kidneys to transport uric acid from the urine. Dogs with mutations in both copies of the SLC2A9 gene are predisposed to have elevated levels of uric acid in the urine, hence the name hyperuricosuria. Dogs with hyperuricosuria most commonly present with symptoms of recurrent urinary tract inflammation, which include frequent urination, blood in the urine, and straining to urinate. They may also have loss of appetite, lethargy, weakness, vomiting and pain. Urinary stones in the bladder can cause urinary tract infections or more seriously, blockage of the Urethra.
Both male and female dogs can be affected, but due to differences in their anatomy obstruction of urine flow is more common in males. Although an x-ray can be used to exclude other types of stones, urate stones cannot typically be seen using x-rays and must be evaluated by ultrasound. Not all dogs with mutations in both copies of the SLC2A9 gene will have symptoms of disease, thought they will have increased uric acid excretion in the urine.
The single nucleotide substitution in the gene called SLC2A9 that causes hyperuricosuria in many breeds is recessive. This means that dogs that carry two copies of the mutation (homozygotes) will almost certainly develop hyperuricosuria during their lives. Dogs that carry a single copy of the mutation (also known as carriers or heterozygotes) will not develop hyperuricosuria as a result of the SLC2A9 mutation, but they will pass the mutation onto about half of any offspring they have. Breeding dogs that will not develop hyperuricosuria 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 hyperuricosuria 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 hyperuricosuria, 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.