health information
An honest overview of the conditions we keep in mind as a breeder: what they are, how they are inherited or transmitted, and how they are detected. Knowledge is the best protection for our cats.
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Healthy breeding starts with knowing what to look out for. Below I discuss the hereditary conditions that can play a role in the Maine Coon, and then the infectious diseases every cat owner should have heard of. Not a scare story, but clear information.
Many of these conditions are inherited polygenetically: not one gene but a combination of weaker genes determines whether a cat develops it. That makes prediction difficult and means we re-test every generation of breeding cats.
Part one
hereditary conditions
Conditions passed on through the genes. For these four we test our breeding cats, because two parents without symptoms are no guarantee of a healthy kitten.
Hip dysplasia HD
HD is a hereditary abnormality of the socket joint in the pelvis, in which the socket is not formed deeply enough. As a result the ball does not fit properly in the joint and the surfaces start to grind against each other. This eventually leads to degeneration of the cartilage, so that bone grinds on bone. That can cause pain when moving.
HD is inherited polygenetically, which makes it hard to predict. Two cats with no signs of HD can together produce a kitten that does develop the condition, and vice versa. Every generation of breeding cats must therefore be tested anew to reduce the chance of HD.
Cats are masters at hiding pain. A cat with HD need not limp at all. Watch instead for more cautious movements, reduced activity or the avoidance of jumping. In a mild form a cat can be entirely free of complaints.
Patellar luxation PL
With PL the kneecaps are not held firmly enough in place and sometimes slip out. There are various grades; depending on the severity, surgery can offer a solution.
Most Maine Coon breeders test their cats preventively for PL. Important here: the test must be carried out without anaesthetic by a vet with specific experience in cats, not only in dogs. The fact that both parents are approved is no guarantee that kittens are free of PL.
This is because the condition is inherited polygenetically. Not one gene but a combination of weaker genes plays a role. Only when a certain threshold is reached does the effect become visible. That explains why parents sometimes do not show the trait while a kitten does have to deal with it.
Hypertrophic cardiomyopathy HCM
HCM is a hereditary heart condition in which the muscles of the left ventricular wall thicken. This disrupts the pumping function and raises the risk of thrombosis and fluid build-up in the lungs and chest.
The only reliable method to detect HCM is an echocardiogram. On death, a post-mortem can give certainty. In Maine Coons the condition sometimes shows itself as early as 6 months of age, but more often only around 2 years. Toms are usually confronted with it earlier than queens.
HCM cannot be cured, but medication can considerably extend life expectancy, sometimes up to 6 years after diagnosis. Treatment depends on the symptoms and may consist of diuretics, heart-supporting medicines or an adjusted diet. Avoiding stress is always sensible.
The condition is inherited autosomal dominantly. If one parent has HCM, statistically at least 50% of the kittens can get it too. The tricky part is that HCM has variable expression: not all affected cats show the same complaints, and some cats pass on the condition without having symptoms themselves. An echo is a snapshot and offers no 100% certainty, but it is so far the only means of monitoring.
Since the end of 2005 there has been a DNA test for the MyBPC3 mutation, which is associated with HCM. This test does not, however, tell the whole story yet. As long as there are cats that later test clear by echo but do carry the mutation, and vice versa, it is not possible to draw conclusions on the basis of this test alone.
Polycystic kidney disease PKD
PKD is a hereditary condition in which fluid-filled cysts in the kidneys gradually expand. As they grow they affect kidney function, which eventually leads to chronic kidney failure. This usually occurs around the age of 7, but can also be earlier.
There are no medicines for PKD. Treatment consists of an adjusted diet to spare the kidneys for as long as possible. The diagnosis is made by ultrasound, preferably from 1 year of age. At that age the reliability of the test is 98%. Have this examination done by an experienced specialist with the right equipment; your own vet is not the right person for this. PKD is inherited dominantly, which means at least one of the parents has the condition.
Part two
infectious diseases
Viral infections that spread between cats. Testing breeding animals and visitors, and providing a calm, low-stress environment, are the main protections here.
Feline AIDS FIV
FIV closely resembles human HIV and is therefore also called feline AIDS. Important to know: FIV cannot be transmitted to humans. The virus spreads through blood or saliva, usually through bite wounds.
The vet can test for FIV with a SNAP test or through laboratory analysis (IF test). In the Netherlands there is no vaccine yet; in America this is now the case.
Feline leukaemia FeLV
FeLV is a contagious viral infection that attacks the cat's immune system, giving all kinds of conditions, including cancer, free rein. The virus spreads through close contact between cats, through bite wounds or matings, via blood or saliva.
Almost all cat associations require a FIV/FeLV test of the stud tom before they issue pedigrees. That test must not be older than one year. The stud owner also asks for this test from visiting queens. Testing can be done with a SNAP test at the vet or through laboratory analysis (IF test).
There is a vaccination against leukaemia, but it does not offer full protection. Most cats diagnosed with FeLV die within three years because they become susceptible to other diseases.
Feline infectious peritonitis FIP
FIP can arise when a common coronavirus mutates into the malignant FIP virus. Stress often plays a role here, for example during a move or a neutering. Although the coronavirus is widespread among cats, only 2 to 10% actually develop FIP.
FIP has two forms. The 'wet' form is characterised by a swollen belly with fluid build-up; the dry form has no swollen belly but shows itself in various complaints that can resemble other conditions.
The diagnosis is very hard to make, because there is no test that confirms FIP with 100% certainty. It is a sum of abnormalities that may or may not fit FIP. That means many other diseases must first be ruled out. With the wet form the diagnosis is relatively the clearest: if the vet draws fluid from the fluid-filled belly and it turns out to be yellow and stringy, FIP becomes very likely.
The FIP virus can be demonstrated through an immunofluorescence test on macrophages in chest or abdominal fluid, or through immunohistochemistry in tissue samples. In addition, since 2014 there has been a PCR test to demonstrate the specific mutation in the virus.
Since June 2023, legal treatment has been possible in the Netherlands with the antiviral GS-441524, via the pharmacy of the Faculty of Veterinary Medicine in Utrecht. It is an ongoing study; the treatment lasts at least 12 weeks and costs several thousand euros, depending on the type of FIP and the dose required. The interim success rate is 80 to 85%.
In closing
This page is intended as general information, not as a replacement for advice from your own vet. If you have doubts about your cat's health, visit a specialist with experience in cats. At PolysRock we re-test our breeding cats every generation, because healthy kittens begin with honest information and careful choices.