By Jennifer Coates, DVM
With so much emphasis being placed these days on understanding our pet’s DNA (what breed are they? Where, exactly, did they come from?), pet parents are naturally beginning to wonder what diseases their companions might have inherited along with their blue eyes or sassy stripes.
Let’s take a look at seven common genetic disorders in cats, their symptoms, which breeds are affected, and how they can be prevented and treated.
In a presentation to the Western Veterinary Conference in 2013, Dr. Jerold S. Bell, adjunct professor of clinical veterinary genetics at the Cummings School of Veterinary Medicine at Tufts University, stated that feline lower urinary tract disease (FLUTD) is the most common feline genetic disorder, occurring “in approximately four percent of all cats (pedigreed and mixed breed).”
Cats are diagnosed with FLUTD when they have typical symptoms (straining to urinate, urinating small amounts frequently, painful urination and urinating outside the litter box) and other potential causes have been ruled out. Genetics isn’t the only cause of FLUTD but combines with risk factors like stress and obesity to determine which cats develop symptoms.
Treatment for FLUTD centers on stress relief, environmental enrichment, keeping litter boxes clean, dietary changes, increasing water consumption and sometimes anti-inflammatory or other medications. No genetic test for FLUTD is available.
Type II diabetes is common in the feline population as a whole, but Burmese cats have a significantly higher than normal incidence due to their genetics. The typical symptoms of uncomplicated diabetes include increased thirst and urination and weight loss despite a good or even increased appetite.
Because no test is available to determine which Burmese cats are at risk for developing diabetes, the general rules of diabetes prevention apply, such as weight management, encouraging exercise and feeding a high protein/low carbohydrate diet. Treatment also involves daily insulin injections.
Cats with polycystic kidney disease have numerous fluid-filled cavities (cysts) in their kidneys. The cysts eventually become so large and/or numerous that cats develop kidney failure, which has early symptoms like increased thirst and urination, poor appetite, weight loss and lethargy. The disease is most common in Persians and Himalayans due to a defective gene that is present at a high frequency in these breeds.
Genetic testing is available for the mutation that causes polycystic kidney disease. Before purchasing an at-risk cat, make sure that the individual or both of its parents have tested negative for the gene. Treatment for cats who have polycystic kidney disease involves modifying the diet, fluid therapy and a variety of medications on an as needed basis.
Hypertrophic cardiomyopathy (a type of heart disease) is caused by identified genetic mutations in Maine Coon and Ragdoll cats. Cats affected with this disease die suddenly or develop heart failure in early or midlife. Treatment for heart failure can improve the quality of life for some cats with hypertrophic cardiomyopathy
Tests are available for the abnormal genes in both Maine Coons and Ragdolls. Prospective owners should only purchase cats who do not carry those genes themselves or who are known to be the result of a breeding between two cats who are not carriers.
Genetic mutations have resulted in Manx cats (and some other breeds) being born with extremely short or absent tails. Unfortunately, these mutations not only affect the bones of the tail but also nearby nervous tissue often resulting in stance and movement abnormalities in the hind legs and urinary and fecal incontinence.
The shorter a cat’s tail is the more likely neurologic dysfunction is too, so unless you plan on showing your cat, pick an individual with a longer tail remnant. There is no treatment for Manx syndrome other than symptomatic care.
White cats with blue eyes are much more likely to be blind than are other cats because of a genetic mutation that not only affects coat and eye color but also the development of structures within the ears. The inheritance of this abnormal gene (called “W” by feline geneticists) is complex, so not every cat who carries it is deaf. Also, white hair and blue eyes can be caused by other genes that do not increase the chances of deafness.
There is not treatment available for deafness caused by the “W” gene, but affected cats can live long and happy lives if they are kept indoors.
Progressive retinal atrophy (PRA), a disease that causes blindness in mid to late life, is known to have a genetic cause in some cats. Two genes are involved in breeds like the Abyssinian, Somali and Ocicat. Tests are available for both genes. Because of their inheritance pattern, it takes two copies of an abnormal gene to cause blindness. Therefore, pre-purchase genetic testing should indicate either that the individual cat in question carries no more than one copy of the abnormal gene or that only one of his or her parents does.
PRA is not treatable but blind cats can live satisfying lives if they are kept in a consistent, indoor-only environment.
Purebred cats are at higher risk for some, but not all, genetic disorders, with certain breeds being worse off than others. Talk to your veterinarian about the genetic “baggage” that might come along with any purebred cat that you are thinking of purchasing or adopting. Find out what reputable breeders should be testing for to reduce the incidence of disease in their breed and ask to see the results of those tests. If they decline, find a different breeder.