Recommendations for Testing and Breeding

There is recommendations avalible for cats tested with echocardiogram as well as with DNA, click here to go to the DNA-recommendations

The following recommendations were worked out for the Maine Coons. Other breeds might be better off with slightly different recommendations, but for now the Maine Coon recommendations are the only ones we have. Hopefully we will get more breed specific recommendations for other breeds too later on.

Recommendations for testing

We have two types of test for some of the breeds in eighter case only DNA is not enough since it covers only one mutation and there are many different, so the DNA needs to be supplemented with a heart screening (ultrasound).

The first HCM test should be done at the age of 1 and before the cat is used in a breeding programme. Further tests are recommended yearly until the cat is over 3 years of age. After that testing is recommended at the age of 5. When it comes to cats which have become very important for the general breeding stock or who are in an especially risky position (equivocal test result or having a close relative who has been diagnosed with HCM) it would be wise to do a test later as well, for example at the age of 8. Please observe that this is just a general point of view which has to be interpreted in each specific case individually.

Recommendations for breeding

Also here the recommendations are a general point of view where you have to look at each specific case individually.

*) Close relatives here means full siblings, parents and direct offspring of the cat.

Normal heart

Cats with a normal heart status according to a test and without any close relatives* diagnosed with HCM can of course be used in breeding from a HCM point of view.

Diagnosed with HCM

Cats diagnosed with HCM of any degree should not be used in breeding.

Cats with equivocal test results

Equivocal means that there was something found in the heart during the HCM test that is not 'normal', but at the time of the test it is not clear whether it is HCM or whether it could develop into HCM or not. It does not automatically mean the cat will develop HCM! Equivocal means exactly equivocal. The anomaly could be caused by other things like high blood pressure, kidney insufficiency, or something else. The cat could also have a normal variation on the 'standard' values, like e.g. the papillary muscles could be a bit larger than those of the average cat. Only further tests will show if this is HCM or not.

Cats which have received an equivocal test result should be handled as follows:

Re-test the cat's heart according to the recommendations of the specialist who examined the cat (it is common that they want to see the cat again in 6-12 months). If the cat is considered equivocal at the re-test, the recommendations depend on the age of the cat at the time of the latest test.

Equivocal, younger than 2 years

If the cat was younger than 2 years of age when the test was done it is not recommended to use this cat as far as breeding is concerned. Instead another test is done when the cat is older than 2 years.

Equivocal, 2-3 years

If the cat was between 2-3 years of age when the test was done one litter can be planned if absolutely necessary, if the cat does not have any offspring earlier. The other parent should of course have a normal heart and not have any close relatives* who have been diagnosed with HCM. These kittens are not allowed to be used in a breeding programme for the time being. This ban on not using these kittens for breeding can be withdrawn if the parent of high risk has a normal heart or is still equivocal at a another test at the age of 3.

Equivocal, older than 3 years

If the cat was older than 3 years when the test was done the cat can be used in a breeding programme but must only be mated to a Maine Coon with a normal heart and who has no close relatives* diagnosed with HCM.

Close relatives of affected cats

If a cat is diagnosed with HCM the following is recommended for its close relatives*:

Close relative has been diagnosed with HCM, the heart is normal on the cat itself when the cat is younger than 2 years:
These cats are not recommended to be used in a breeding programme until it has been approved for breeding after another test at the age of 2.

Close relative has been diagnosed with HCM, the heart is normal on the cat itself at the age of 2-3 years:
One litter at the most is here recommended if the cat has no offspring earlier. The other parent should then have a normal heart and have no close relatives* diagnosed with HCM. The kittens in this litter is not to be recommended for breeding for the time being. These non breeding recommendations can be withdrawn if the parent of high risk still is showing no sign of HCM at the age of 3.

Close relative has been diagnosed with HCM, the heart is normal on the cat itself when the cat is older than 3 years:
If the cat still has shown no sign of HCM at the age of 3 the cat can be used in a breeding programme. It should however preferably be mated to a Maine Coon which is a risk free partner (not equivocal or cat with a close relative* diagnosed with HCM).

If the cat has been diagnosed with an equivocal heart and also has a close relative being diagnosed with HCM you should be extra cautious.

Help!

If you feel unsure about what applies for your cat, please don't hesitate to contact the contact persons for the health program!

Breeding recommendations for cats tested with DNA!

We propose the following recommendations regarding genetic testing for HCM1:

• It is recommended that all Maine Coon cats which are to be used for breeding are tested to determine their status, unless the cat's parents are both known to be negative for the mutation.
• It is not recommended to use this gene test for cats of any other breed, unless they have Maine Coon cats behind them in their pedigree, as this particular mutation has so far only been found in Maine Coons and cats related to Maine Coons.
• It is recommended to continue to screen the cats with ultrasound because that will help to detect cats with HCM caused by a mutation other than HCM1.
• Breeding decisions should be made carefully. At this time the labs have reported about 33-35% positive among the Maine Coon cats that they have tested. This means that about one third of all Maine Coon cats seem to have at least one copy of the gene. Removal of all of these cats from the breeding population could be very dangerous for the future health of the breed. For this reason, it is NOT recommended that all cats heterozygous for the mutation (have ONE copy of the mutated gene) should be immediately removed from the breeding program. Heterozygotes can be used, if the cat is considered important for maintaining genetic variation. Since there is presently no objective way to say exactly which cats are important to maintain genetic variation and which are not, it will have to be up to the individual cat owner to use his/her own judgement here. A heterozygous cat should only be bred to an unaffected negative cat, to decrease the risk of producing affected cats. With progress, negative kittens from these lines should be selected for breeding.
• It is not recommended to use homozygous cats (have TWO copies of the mutated gene).

Keep in mind that the scientific progress in this area is high and that recommendations may be altered, as more information becomes available.