Cystinuria (Australian cattle dog type) is an inherited disease affecting kidney function in dogs. The SLC3A1 gene codes for a protein that allows the kidneys to transport cysteine and other amino acids from the urine. Normal kidneys reabsorb the Amino Acid cystine so that only small amounts pass into the urine, while dogs with mutations of both copies of the SLC3A1 gene fail to reabsorb cystine allowing large amounts to pass into the urine, hence the name cystinuria. Cystine can form crystals and/or stones in the urinary tract which can block the ureters or Urethra and stop the normal flow of urine. Symptoms of disease include straining to urinate, frequent urination of small volumes or inability to urinate. In dogs, males and females are equally affected with excess cysteine in the urine, but obstruction of urine flow is more common in males due to differences in anatomy. Similar to other dominant diseases, affected dogs have variable onset and severity of clinical signs depending on the number of inherited copies of the cystinuria associated Mutation. Dogs inheriting two copies of the mutation (one from each parent) have a higher concentration of cysteine in their urine than dogs with only one copy and tend to develop symptoms associated with cystinuria earlier. Dogs with cystinuria often have recurrent inflammation of the urinary tract and if not treated, urinary stones can cause urinary tract infections, kidney failure and even death.
Breed-Specific Information for the Australian Stumpy Tail Cattle Dog
Australian stumpy tail cattle dog is included as a breed susceptible to cystinuria (Australian cattle dog type) because of its close relatedness to the Australian cattle dog breed, which is known to develop this disease due to Mutation of the SLC3A1 gene. The frequency of the causal mutation in the general Australian stumpy tail cattle dog population is unknown.
Genetic testing of the SLC3A1 gene will reliably determine whether a dog is a genetic Carrier of cystinuria (Australian cattle dog type). Cystinuria (Australian cattle dog type) is inherited in an Autosomal Dominant manner in dogs meaning that they only need to inherit one copy of the mutated gene from a parent to develop the disease. Dogs identified to have the genetic Mutation are expected to have features of the disease, though symptoms can be very mild and dogs may appear healthy. Each pup that is born to a single affected parent has a 50% chance of inheriting one copy of the SLC3A1 gene mutation and having the disease. If both parents are affected, the chance of having affected offspring increases to 75-100%. Reliable genetic testing is important for determining breeding practices. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers is not recommended. Dogs that are not carriers of the mutation have no increased risk of having affected pups.
There may be other causes of this condition in dogs and a normal result does not exclude a different mutation in this gene or any other gene that may result in a similar genetic disease or trait.
Brons AK, Henthorn PS, Raj K, Fitzgerald CA, Liu J, Sewell AC, Giger U. SLC3A1 and SLC7A9 mutations in autosomal recessive and dominant canine cystinuria: A new classification system. J Vet Intern Med. 2013 Nov;27(6):1400-8. doi: 10.1111/jvim.12176. Epub 2013 Sep 3.