Mode of Inheritance
Cystinuria is a genetic disease in the
kidney tubules. Normal kidneys filter the amino acid cystine and do
not allow it to go into the urine. In dogs with cystinuria, this
filtering action fails, and cystine passes into the urine, where it can form
crystals and /or stones. If stones form, they can block the urethra
and obstruct urinary flow, especially in males.
Newfoundlands inherit this disease in an
autosomal recessive fashion, meaning that both parents of an affected dog
were either affected or carriers themselves. Each parent passed one
mutant gene to their offspring. A cystinuria carrier is a perfectly
healthy dog. A cystinuria carrier will never be affected by
cystinuria, although a carrier bred to a carrier can produce cystinuria
affected pups. A carrier bred to a normal/clear dog, can only produce
other carriers, or normal/clear pups.
It is very important to know whether each
dog is normal/clear, carrier or cystinuria affected. A DNA test is
available to Newfoundland and Labradors. Responsible breeding decisions can be made
based on this information.
Given the availability of this DNA test, there is no reason that a Newfoundland should ever be affected by cystinuria today.
*It is important never
to breed two carrier dogs, because on average 25% of the pups could be
affected. One parent should always be clear/normal for the disease