In 2006, the Rhodesian Ridgeback Club of the United States solicited DNA samples of Ridgebacks with juvenile cataracts to be sent to Dr. Cathryn Mellersh of the Animal Health Trust in England.

Dr. Mellersh and her colleagues have successfully isolated the genetic mutation that causes hereditary cataracts in Staffordshire Bull Terriers. She requested DNA samples from other breeds to see if they shared the same mutation.

Six samples of affected Rhodesian Ridgebacks, and another six samples of carriers, were sent to England.

“We have tested all six dogs for the mutation we have identified in other breeds, and unfortunately none of the affected dogs carried the mutation,” Dr. Mellersh reports.

Though the lab likes to test 10 to 12 dogs before formally excluding a particular mutation from any breed, “I think we can be fairly sure we need to search for the different mutation [in the Ridgeback], given 6 out of 6 were clear,” she concludes.

What this means is that the gene that causes heritable cataracts in Rhodesian Ridgebacks is different from the one that causes the diseases in Staffordshire Bull Terriers.

If she receives more samples of affected Ridgebacks and their relatives, Dr. Mellersh can look for our breed’s specific marker. This would result in a test that would allow breeders to identify carriers for the disease and, through careful breeding, eliminate the disease expression in our breed population.

Dr. Mellersh needs samples from at least 14 more affected dogs as well as their close relatives, which include parents, siblings (both affected and unaffected) and grandparents.

If you own or have bred dogs that would be helpful to this study, please contact RRCUS Health & Genetics Chair Susan Ralston at As always, all information is held in the strictest of confidence.

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