Manx cat care: the tailless gene and Manx syndrome

The Manx's missing tail comes from a single copy of a gene variant that shortens the spine, and in some cats it shortens more than the tail. About one in five short-tailed Manx has at least one other congenital defect, and roughly 90% of those defects occur in completely tailless ("rumpy") cats. Most problems show up in kittenhood, so the first months are when a buyer or new owner should watch most closely.

Where the tail, or its absence, comes from

The Cat Fanciers' Association breed profile describes the Manx as an ancient breed from the Isle of Man, recorded by visiting sailors in the sixteenth century. It has a short back that arches to a round rump, hind legs much longer than the forelegs, and males weigh 10 to 12 pounds (4.5 to 5.4 kg), with females smaller.

Taillessness is dominant. A 2013 genetic study of Manx cats from the US and the Isle of Man traced it to several different mutations in the T gene, which codes for a protein called Brachyury that guides development of the spine. Ninety-five percent of short-tailed Manx carried one mutant copy. Two copies are thought to kill the embryo early, which is why litters from two short-tailed parents are often small. One copy gives a tail of unpredictable length: in that study, one male sired kittens with all four tail types in a single litter.

Only the completely tailless cat can be shown under the CFA standard. The CFA notes that breeders regularly use tailed Manx in their programs and, together with checking kittens for health problems, credits this with keeping the breed's gene pool healthy and diverse. Fully tailed cats rarely carry a variant (1 of 49 in the 2013 study did), so pairing one with a tailless cat also avoids most of the embryo losses expected from two short-tailed parents.

Manx syndrome

"Manx syndrome" is the name for the defects of the lower spine, spinal cord and nerves that can come with taillessness. The 2013 study lists sacral agenesis or dysgenesis (a missing or malformed sacrum), absence of the sacral spinal cord, a tethered spinal cord, and imperforate anus among them. In breeding experiments with rumpy and stumpy cats in the 1970s, researchers confirmed dominant inheritance and proposed that spina bifida, urinary and fecal incontinence and hind-limb gait problems may all stem from a disturbance in early development of the nervous system.

Spina bifida, an incomplete closure of the spinal canal, is one part of the picture. A veterinary review of spina bifida names the Manx cat as a predisposed breed and notes that the defect is often clinically silent. When it does cause signs, recognizing them early matters: imaging confirms the diagnosis, and in selected cats surgery may be considered to prevent neurological decline.

Signs to watch for in a Manx kitten or young cat:

• Soiling, dribbling urine, or a constantly wet or dirty back end.
• Straining to pass feces, very hard stools or long gaps between bowel movements.
• A hopping gait, weakness, wobbliness or dragging of the back legs.
• Reduced feeling or reaction around the tail base and hindquarters.
• No visible anal opening, or a kitten that is not passing feces at all, which is an emergency.

Any of these needs a vet visit. A cat that is otherwise well may still have a malformation that shows on X-rays, so ask for a careful check of the spine and hind-leg reflexes at the kitten vaccinations. Before buying, ask the breeder about Manx syndrome in the lines, as the CFA advises, and meet the kitten when it is old enough to walk and use a litter tray normally.

How much to feed

Manx cats have no special nutrient needs that we could find evidence for. The main job is keeping a round, deep-bodied cat at a lean weight. The Merck Veterinary Manual's standard estimate starts with resting energy requirement (RER), 70 multiplied by body weight in kilograms raised to the power 0.75, in kcal a day. Neutered adult cats are fed about 1.2 times RER, intact adults 1.4 times, and cats prone to obesity 1.0 times. Rounded to the nearest 5 kcal:

Start from the ideal weight, not the current one, and adjust over several weeks. The Manx's arched back and round rump make it look heavier than it is, and a cat that is actually fat can pass as "just the breed shape." Feel for the ribs, which should be easy to find under a thin layer of fat, and weigh the cat once a month on a kitchen or baby scale. Growing kittens need far more per kilogram; Merck puts them at about 2.5 times RER, or free-choice feeding.

Bowel and bladder care

Because the defects range from silent to severe, some Manx show only mild bowel or bladder trouble. The practical signs are chronic constipation, occasional soft stools or accidents outside the tray, and urine scalding around the back end. There is no breed-specific diet with evidence behind it, but a few habits help any cat prone to constipation:

• More water. Wet food, several water bowls and a fountain all raise fluid intake, and well-hydrated stools are easier to pass.
• A known baseline. Note how often the cat normally passes stools and what they look like. A day or two without a bowel movement, or straining in the tray, is easier to spot against that record.
• Fiber and laxatives only with a vet. Added fiber helps some constipated cats and worsens others, depending on the cause, and a cat with poor nerve supply to the colon needs a plan rather than guesswork.
• A clean, easy tray. A low entry and roomy tray suit a cat with weak hind legs. Gently clean and dry the back end of a cat that soils itself.

Straining in the litter tray with little or no urine is an emergency in any cat, especially a male, because it can mean a urethral blockage.

Joints and mobility

Arthritis is common in older cats of every breed, and it is easy to miss because cats rarely limp. A Manx that stops jumping onto favorite spots, uses the stairs slowly, grooms its back end less or starts missing the litter tray may be in pain. Those changes deserve an examination, since effective pain relief is available. Keeping the cat lean is the one thing food reliably does for its joints; joint supplements for cats have limited evidence and should not replace that visit.

Eyes

A 1976 report described an apparently inherited corneal dystrophy in an inbred line of Manx cats. The first changes, swelling of the front layers of the cornea, appeared at about four months of age and worsened to fluid-filled blisters and breakdown of the corneal surface. It was described in one line, and we found no data on how common it is in the breed today. A cloudy, bluish or blistered cornea, squinting or a watery eye in a Manx of any age needs a vet, and possibly a veterinary ophthalmologist.

Play and daily life

The CFA describes the Manx as a quiet, devoted companion with bursts of play. The powerful hind legs make it a strong jumper, so cat trees, wall shelves and wand-toy games suit most Manx well. Watch how the cat moves during play: a change in its willingness to jump is often the first sign of back or hip pain. Puzzle feeders give some of the daily ration a job to do and slow a fast eater.

Sources

1. Manx. The Cat Fanciers' Association.
2. Multiple mutant T alleles cause haploinsufficiency of Brachyury and short tails in Manx cats. Mammalian Genome, 2013.
3. Malformations and the Manx syndrome in cats. Canadian Veterinary Journal, 1979.
4. Spina Bifida, Meningomyelocele, and Meningocele. Veterinary Clinics of North America: Small Animal Practice, 2016.
5. Hereditary corneal dystrophy in the Manx cat: a preliminary report. Investigative Ophthalmology, 1976.
6. Nutritional Requirements of Small Animals. Merck Veterinary Manual.