Hypertrophic cardiomyopathy (HCM) is a condition characterized by thickening of the heart muscle (wall of the ventricles of the heart). This results in a reduced volume within the ventricles (major chambers of the heart), so reducing the volume of blood that the heart can pump with each contraction. Hypertrophic cardiomyopathy is the most common form of heart disease in cats and can cause heart failure, thromboembolism, and occasionally sudden death in cats (see also Cardiomyopathy in cats).
Is HCM genetic? Hypertrophy (thickening) of the ventricles can occur secondary to certain other diseases in cats (such as hyperthyroidism and hypertension), but most cases are idiopathic (i.e., have no obvious underlying cause) and are considered primary diseases of the heart itself. The majority of cases of HCM in humans are recognized to have a genetic basis, with over 130 genetic mutations already identified that may cause or predispose an individual to development of the disease. It is now believed that many cases of HCM in cats may also have a genetic basis. Specific genetic mutations have been identified in both the Maine Coon and Ragdoll breeds of cat.
Mutations in the gene responsible for producing a particular protein in heart muscle cells – MYBPC3 (the cardiac myosin binding protein C gene) have been identified commonly in both Maine Coon and Ragdoll cats affected with HCM (a different mutation is present in the two breeds), and similar mutations may also be seen in some other breeds. It appears that the presence of the defective gene increases the risk of a cat developing HCM. Genes are inherited in pairs, and if a cat has two defective (mutated) genes (called a homozygous cat) this increases the risk of HCM further compared with a cat that has just one defective gene (and one normal gene, a heterozygous cat). These gene defects are common in Maine Coon and Ragdoll cats, with some studies showing up to 30-40% or more of cats carrying one or two defective genes. However, the relationship between the presence of the mutated gene and the development of HCM is not perfect. The gene defect appears to increase the risk of disease, but not all cats with the defect develop HCM and some cats in these breeds that develop HCM do not have these defects. It is likely that other (as yet unidentified) gene defects and other environmental and biological factors all influence the development of HCM.
Ultrasound testing of the heart to measure the thickness of the heart wall and to determine the presence of HCM is used along with the gene tests (which are available from a number of laboratories) to characterize cats. A further problem can be that some affected cats may not develop changes detectable on ultrasound examination of the heart until later in life, and some changes may be mild and subtle. Using the gene test and ultrasound scanning in breeds such as the Maine Coon and Ragdoll (where an important gene defect predisposing to HCM has been identified), it is recommended that cats should ideally be screened by ultrasound examination of the heart, and also have a blood sample/cheek swab taken. Samples are then sent to a specialist veterinary laboratory to determine the genetic status of the cat.
It is recommended that: Cats clinically affected with HCM on the basis of an ultrasound scan should not be bred from Any cat with a positive gene test that is homozygous for the defect (has two abnormal genes) should not be bred from as they will always pass on the abnormality to their offspring. Careful consideration needs to be taken in breeding from cats that are heterozygous positive on the gene test (have one normal gene and one mutated gene). These cats will inevitably pass on the defect to a proportion of their kittens When selecting cats for breeding, there are many different considerations to take into account. The high prevalence of both clinical disease and the gene defect in breeds such as the Maine Coon and Ragdoll means that great care must be taken to try to reduce the frequency of the gene defect in these breeds and so reduce the risks of HCM developing. HCM can occur at any age and therefore a single normal echocardiogram (ultrasound examination of the heart) does not guarantee that the cat will remain free of the disease. Cardiologists recommend that breeding cats should have an annual echocardiogram during their breeding years. Examining retired cats periodically is also advantageous as this may allow the identification of affected cats that have offspring in a breeding program.
There is ongoing work looking for further mutations that may contribute to HCM in Maine Coon and Ragdoll cats, along with other breeds such as the Norwegian Forest Cat and the Sphynx where a higher prevalence of HCM has been reported or suggested.
All our breeding cats are tested for this gene.
( Source : International Cat Care. org)
Spinal Muscular Atrophy in Maine Coon Cats (SMA) SMA is an inherited disorder affecting the skeletal muscles of the trunk and limbs. Loss of neurons in the first few months of life leads to muscle weakness and atrophy that first becomes apparent at 3-4 months of age. Affected kittens develop an odd gait with a sway of the hindquarters and stand with the hocks nearly touching. They may also stand with toes out in the front. By 5-6 months of age they are too weak in the hindquarters to readily jump up on furniture and often have a clumsy landing when jumping down. The long hair Maine Coon may hide it, but careful feeling of the limbs will reveal reduced muscle mass. Affected kittens are not in pain, they eat and play avidly, they are not incontinent, and most live very comfortably as indoor cats for many years. Known affected kittens have occurred in breeding programs across the United States, and, in retrospect, likely carriers have been exported widely.
Onset of clinical signs is observed between 15 and 17 weeks of age. Initial abnormalities are hind limb weakness and a fine generalized tremor. Affected kittens lose the ability to jump strongly by five months and walk thereafter with a sway of the hindquarters. Abnormal sensitivity to touch over the back, exercise intolerance, and labored breathing are variably observed. After an initial period of rapid loss of function, the progression of the disorder slows or plateaus with variable muscle atrophy, weakness and mobility.
Mode of inheritance:
This disorder is inherited as a simple autosomal recessive trait. For a kitten to have the SMA disorder, it must receive the mutated copy (allele) of the disease gene from both parents, and male and female kittens are equally affected. The parents of affected kittens show no outward signs of disease, but they are obligate carriers.
The disease is inherited as an autosomal recessive, thus 2 copies of the mutation are required to produce the disease and both males and females are equally affected. SMA in Maine Coon cats is caused by a large deletion of chromosome 1. Testing to identify both affected cats and carriers assists breeders to avoid future matings that can produce affected kittens.
All our breeding cats are tested for this gene
Erythrocyte pyruvate kinase deficiency (PK deficiency) is an inherited hemolytic anemia caused by insufficient activity of its namesake regulatory enzyme.
It was only quite recently discovered in Maine Coons as well as a lot of other breeds. It seems around 15 % of all Maine Coons carry this mutation. Testing for it is very easy via DNA. Only animals with “the double gene” (homozygous positive) are affected and will likely get ill. As long as breeders do not breed carrier to carrier, the animals will stay healthy.
All our breeding cats are tested for this gene.
Polycystic kidney disease is caused by an inherited autosomal dominant gene abnormality, whereby the kidneys do not develop correctly. This ultimately leads to multiple cysts forming in a cat’s kidneys.
Cats only need one parent to be infected with the defective gene, to inherit PKD. In fact, without DNA testing it may not even be evident that a breeding cat is carrying the defective gene at all. This is because they may only be a carrier of the gene, therefore showing no signs or symptoms of the genetic defect.
PKD Symptoms In Cats The signs and symptoms of Maine Coon polycystic kidney disease are very similar to those present when a cat is suffering from chronic renal failure.
All our breeding cats are tested for this gene.
Blood type B
Most Maine Coons have blood type (blood group) A.
Blood type B also exists, and it is a recessive trait. It means some cats with blood type A are carriers of B. Around 3 % of Maine Coons are B, whereas around 15 % are carriers of B and can produce B kittens if mated.
Blood type B is not a disease, however breeding queens with blood type B males can create huge problems for her kittens, so we do not wish to use B cats in our breeding.
All of our breeding cats have their blood type DNA
HD – Hip Dysplasia is a hereditary disease that causes problems with the hip joint. All large breeds of cats and dogs are at risk for Hip Dysplasia (HD). Several cats have it in a mild form that the animal can live well with, but it should not be used for breeding. In severe form HD is a very painful and disabling disease, and in the worst cases lead to euthanasia. What is known is that the risk of getting a cat with HD is much smaller if both parents have normal hips. This is no guarantee, but it betters the chances.
HD is believed to be recessive and polygenetic. Approximately 10 % Of Maine Coons have moderate or severe HD and should not be used for breeding.
Offspring from Normal-Normal combinations have much lower risk for serious HD. Breeding cats should be scanned for HD at the age of 1 year old. Then retested once a year until they are 4 years old.