It is readily evident that the lifestyle in these beginning years of the 2nd millennium AD, is not promoting good health for humans or pets. Both the human and the cat are sedentary, not needing to search for food or shelter, and enjoying longer lifespan than ever before. Unfortunately, there is a price being paid and it is at the expense of health.
Diseases associated with over nutrition and inactivity, complicated by aging, are at epidemic proportions. Obesity leads the pack, but close behind are cardiovascular disease, arthritis, diabetes and cancer (not necessarily in that order).
There are signs along the road to disease, warning of potential disaster, in the guise of body weight , glucose levels, and radiographic changes among others. These are identified as "biomarkers", serving as biological check stations where flags can be posted when physiological activities are off kilter. The key is that we have to actively look for these markers.
Other signs are recognized as "endpoints", such as pain or mobility. These signs are clearer indications that something is wrong, but offer little diagnostic help.
"Bioactives" are nutrients that can have a biological effect, apart from and in addition to the nutritional benefits they provide. The impact that these bioactives have on the biomarkers and endpoints, is the active stage of nutrigenomics currently underway. In the future, the genetic phase will provide the means to analyze an animal's DNA preemptively, identify the diseases that are likely to develop, and point to prophylactic changes in nutrition that can be used to prevent those diseases from occurring.
In cats, armed with the knowledge that obesity and diabetes are prevalent, we can selectively control their diets. Also, with routine veterinary exams, it is possible to find those biomarker "flags" which empower us to take proactive steps in disease control.
Not all diseases are genetic in nature, and of those that are, not all are manageable through nutrition.
Cats as a species tend to have fewer genetic diseases than dogs, quite possibly due to a more homogeneous genetic pool. There is just not as much physical diversity in cats as seen in dogs. Over 100 diseases have been recognized as genetic in nature in cats, whereas dogs have over 400. Some of the genetic diseases have a higher prevalence in certain breeds. That is not surprising, since the animals within a breed share a smaller pool of genes. Let's take a look as some of these genetic diseases and the breeds associated.
The Scottish Fold breed developed due to a genetic mutation that affects the cartilage in the ears, resulting in the ear flap folding forward. However, when this version of the mutated cartilage gene is present from both parents, many of the offspring develop severe crippling lameness early on. Radiographs show abnormalities affecting the growth plates of the leg bones (this would be a biomarker). However, it is usually plain to see outwardly that the affected cats have shortened, malformed legs. To offset this defect, breeders in America determined that by breeding cats with folded ears to Scottish-type cats having normal ears, the offspring (who are then heterozygous for the cartilage gene) were relatively normal and that half of them have the breed characteristic folded ears without the early devastating severe crippling lameness seen when in breeding two folded-ear cats together (where the offspring are homozygous for that gene). The mutated cartilage gene does not have expression limited to the ear cartilage, but affects cartilage throughout the body. Unfortunately, even the heterozygous offspring become afflicted with progressive arthritis later in life, which will vary in severity from animal to animal.
A genetic disease that is seen in all breeds of cats is Polycystic Kidney Disease (PKD). There has been noted a higher prevalence of PKD in Persian cats and other long-haired, pure-bred cats related to Persians. Quite simply, cysts develop within the kidneys, getting larger and more numerous as the cat ages. As the cysts take up more room in the kidneys, there is ever decreasing functional tissue. Eventually, limited kidney function deteriorates to kidney failure. The gene involved has such a potent affect, that those animals that are homozygous (they received the same "bad" gene from each parent) will not survive past kitten hood, many dying before birth. The heterozygous cats are the ones that will live to maturity and beyond. Clinically, the disease does not make itself known until the afflicted animal is already of breeding age.
Luckily, ultrasonography can be used to screen all pure-bred long-haired cats at about 12 months of age. The presence of three cysts or more between the two kidneys indicates the presence of PKD. Breeders can use this valuable tool to find which of their potential breeding animals may carry the gene and then spaying or neutering that animal to prevent proliferation of the gene. Theoretically, PKD could be eliminated this way.
There is a genetic disease in Devon Rex cats which causes a muscle disorder, called spasticity. It takes two identical genes to be present for the disease to manifest itself, indicating that both of the parents are carriers for the disease. It is readily apparent when a cat is afflicted as the animal shows locomotor problems between 6 weeks and 20 weeks of age. The head and neck are the regions most affected. The characteristic signs serve to diagnose the affected cat. Unfortunately, there is not yet a genetic test to identify the carriers. The carriers are heterozygous for the responsible gene, having a normal "good" gene and a "bad" gene present. Outwardly, the cat appears totally normal. When that animal breeds, it is going to pass on either the good or bad gene. Because of this, when a spastic cat is born, it is obvious that both parents are carriers. Therefore, it is best if those two animals and all of the kittens from that breeding are spayed or neutered to prevent future breeding.
Part of the effort towards improving the health of our cats, is in finding those genetic diseases that are impacted nutritionally. Through genetic testing where possible, selective breeding and nutritional management, breeders play a key role in decreasing, possibly even eliminating, genetic diseases in their cats breed.