Manx (cat) - Genetics and Health

Genetics and Health

The Manx taillessness gene is dominant and highly penetrant; kittens from two Manx parents are generally born without any tail. Being homozygous for (having two copies of) the gene is semi-lethal and such kittens are usually spontaneously aborted before birth. Thus, tailless cats can carry only one copy of the gene. Because of the danger of having two copies of the taillessness gene, breeders avoid breeding two entirely tailless Manx cats together. Because neither parent carries the tailless allele, a tailed Manx bred to a tailed Manx results in all tailed kittens. Breeders have reported all tail lengths in the same litter, and there is no accurate means to predict the ratio of tailed to tailless kittens produced in each litter.

Some partial tails are prone to a form of arthritis that causes the cat severe pain, and in rare cases Manx-bred kittens are born with kinked short tails because of incomplete growth of the tail during development; kittens with stumpy to long tails have sometimes been docked at birth as a preventative measure.

"Manx syndrome" or "Manxness" is a colloquial name given to the condition which results when the tailless gene shortens the spine too much. It can seriously damage the spinal cord and the nerves causing a form of spina bifida as well as problems with the bowels, bladder, and digestion. Very small bladders are indicative of the disease and it is often difficult to diagnose. Death can occur quite suddenly and some live for only 3-4 years; the oldest recorded was 5 years when affected with the disease. In one study it was shown to affect about 30% of Manx cats, but nearly all of those cases were rumpies, which exhibit the most extreme phenotype. Such problems can be avoided by breeding rumpy Manx cats with stumpy specimens and this breeding practice is responsible for a decline in spinal problems among modern, professionally bred Manx cats today. Most pedigreed cats are not placed until four months of age (to make sure that they are properly socialised) and this usually also gives adequate time for any such health problems to be identified. Renowned feline expert Roger Tabor has stated: "Only the fact that the Manx is a historic breed stops us being as critical of this dangerous gene as of other more recent selected abnormalities." The breed is also predisposed to rump fold intertrigo and corneal dystrophy.

Some tailless cats such as the Manx cats may develop megacolon which is a reoccurring condition causing constipation that can be life threatening to the cat if not properly monitored by the owner and the vet. In a majority of cases, it may be idiopathic. It is a condition in which due to absence of a tail, the smooth muscles that normally contracts to squeeze out the feces toward the rectum loses its ability to do so.