Veterinary care for cats is getting more advanced year on year. No longer are we restricted to a quick prod, temperature check and listening with a stethoscope (sorry Mr Herriot!). One of the most modern tests in a vet’s arsenal is genetic testing. Today we will discuss what genetic testing is, why you might want to perform one, and what tests are available for cats.
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What is Genetic Testing?
Genetic testing is a type of test that looks at the DNA of an animal. DNA is the base building block of genes. Every gene in an animal’s body codes for a specific trait. One will code for fur colour, another for gender, another for their risk of getting certain diseases. Almost everything that makes your cat them is determined by their genes (at least at birth – many other factors also affect your cat once they are born, such as environment, diet and health). By using a genetic test, we can determine which genes are present and how this affects your cat.
There are different ways of performing a genetic test. When performed at a vet’s practice, many genetic tests require a small amount of blood and are sent to external laboratories. Other samples can be submitted depending on the test desired. There are also an increasing number of at-home genetic tests where owners can swab the inside of their cat’s cheek and pop it in the post, getting a list of their cat’s genetics in return.
Why Would You Perform It?
There are two main reasons why a cat owner may want to test their cat’s genetics.
The first may be to determine what sort of cat they are.
Every breed will carry different genes, meaning a cat’s breed can be determined by their genetics. This may be interesting for some people. But it can also determine breeding and help vets consider likely diseases (some diseases are more common in certain breeds).
The second is to identify their risk of disease, or diagnose diseases.
Many diseases are linked to inheritabale genes that can be passed to offspring. Carrying some of these genes is linked to a higher risk of certain diseases. Knowing if your cat is at risk of a certain disease allows you and your vet to monitor regularly for the early warning signs, help diagnose it early and even guide treatment. Some diseases may even be diagnosed via these tests. Knowing the risk of genetic diseases also helps with breeding; two cats can be tested to determine the risk that their kittens will carry genes for certain diseases. Via breeding programmes using genetic testing, the incidence of some of these diseases is being dramatically reduced.
Some tests will also test your cat’s blood type. This is useful if they ever need a blood transfusion, or are brave enough to donate blood to a cat in need. However, testing a cat’s blood type can easily be done using simpler tests at a vet’s practice. So it’s a nice extra for genetic testers to offer this, but not essential.
Is It Accurate?
We cannot comment on the accuracy of the testing provided by some of these companies. So do use caution and preferably stick to tests recommended by your vet rather than online companies. In fact, we have written an article discussing the reliability of genetic testing in dogs; many of the points are the same in cat genetic testing. In particular, DNA testing for breed is fraught with controversy. There is a lot we don’t yet know about breed gene frequencies, so take these results with a pinch of salt.
However, even with disease testing, there are caveats. Just because a cat carries a gene for, say, heart disease, does not mean they have or will ever get heart disease. Heart disease is a complex disease and no one gene causes it. Other factors play a huge effect too. A cat carrying a gene for heart disease is instead more likely to have heart disease later in life than one without. The tests also tend to be very specific, looking at one particular gene or sequence of genes. Many other genes may also play a role in certain diseases, and can be missed. A cat lacking the gene for heart disease may still get some form of heart disease in life (even if it isn’t the specific genetic form of the disease).
What Diseases Can be Tested For?
This list is by no means exhaustive. Many companies may offer other tests for different diseases, and it may vary if you are not from the UK. Furthermore, more and more diseases are able to be tested for as the science advances, so new tests may be available in future. Here are just a few that you might test for.
Polycystic Kidney Disease (PKD)
This is one of the more common genetic diseases we see as vets; most common in Persian cats, though it can also be seen in Himalayan, Siamese, Ragdolls, European, American and British shorthairs, Scottish folds and other cats. This condition causes fluid-filled cysts to form on your cat’s kidneys. Over time, these can grow and start to affect the kidneys’ functions. This can lead to kidney failure, usually much earlier than in normal cats, from around seven years old.
Unfortunately, there is no treatment, but identifying the gene for PKD early means a cat can be monitored regularly for kidney function. And they can be put onto special kidney-protecting diets earlier, helping keep the kidneys healthier for longer. Without the genetic test, diagnosis is usually only possible once the cysts are big enough to be seen via ultrasound, by which time the kidneys may already be irreversibly damaged.
Hypertrophic Cardiomyopathy (HCM)
Hypertrophic cardiomyopathy is the most common heart condition in cats; where the heart muscles start to thicken, reducing the volume of the heart, meaning it has to work harder, leading to further thickening. If untreated, it can lead to fluid building up in the lungs and abdomen, difficulties breathing, collapse, heart failure and death. Cats with high blood pressure, hyperthyroidism, kidney disease and others are more prone to HCM. However, there are genes that increase the risk of HCM earlier in life, and these can be tested for in Maine Coons and ragdolls.
Just like polycystic kidney disease, the earlier HCM is spotted, the better the prognosis. This means knowing that your cat is at greater risk of HCM allows your vet to monitor them regularly and start early treatment.
Progressive Retinal Atrophy (PRA)
Progressive retinal atrophy describes a condition where the retina of the eye (where light is detected and sent to the brain for processing) slowly starts to deteriorate. This leads to eventual blindness as early as a few months old. It can occur due to other, unknown causes (possibly another gene). But a cat that carries both copies of the PRA gene will develop the disease. Unfortunately, there is little that can be done at this stage, but it means breeders can prevent this cat from passing the gene on to offspring. It is more common in Persian, Abyssinian and Bengal cats.
Gangliosidosis
Gangliosidosis is an unusual and sadly fatal brain disorder seen in Burmese, Korat, Siamese and standard domestic cats. Cats with this disease lack an enzyme required to break down fats – the fats are instead stored inside cells, which disrupts the cells’ functions. Crucially, the fats can be stored inside neuronal cells in the brain and nervous system. This leads to neurological signs like ataxia (wobbliness or “drunkenness”), tremors, unusual eye motions and blindness, seizures, weakness and death, usually under a year old. As with PRA, it cannot be cured, so genetic testing is important to prevent the gene being passed on to kittens – a cat can carry one copy of the gene as a non-diseased carrier, or have both and suffer from gangliosidosis
Spinal Muscular Atrophy (SMA)
Spinal muscular atrophy is a condition of Maine Coon cats that results in the nerves to the limbs being lost. This leads to weakness, paresis and even paralysis. Cats like this are generally not safe to be left outdoors, and may struggle indoors, but can go on to have relatively normal lives with owner assistance. It first becomes obvious around 3-4 months of age. Once again, a cat can be a carrier but not diseased, or carry both genes and be affected – genetic testing, therefore, is important for breeding rather than individual health, though it can help identify the disease if a Maine Coon starts to become weak for an unknown reason.
Closing Thoughts
As with dogs, genetic testing in cats is a relatively new but increasingly useful tool for identifying disease or risk of disease. Many of the diseases that are tested for are debilitating, painful, life-threatening or even fatal. By using genetic testing, we can identify the risk in individual cats, to prepare you and us for management, as well as try and reduce the risk of the disease being passed to offspring. Given time, we may even be able to make some of these diseases a thing of the past, thanks to genetic testing. If you are the owner of any of these exotic cat breeds, please speak to your vet today about whether genetic testing is right for your cat.
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