Which breeds are affected?
Absolutely ALL breeds of cat can sporadically produce kittens with thoracic deformities, including non-pedigree cats. However, some breeds, seem to be more prone to the problem, or their breeders are perhaps more open about discussing it. FCKS is one of the better-known deformities partly because it is estimated that approximately 50% of affected kittens die from the condition. Breeders from every country in the world have had experience with FCKS, so there are no boundaries and it could happen to anyone. It is very important to understand that these deformities are nobody's fault. Kittens with FCKS and/or other thoracic deformities can turn up completely unexpectedly in matings that have never had problems before.
Why does FCKS happen?
This is the most important question that we need to answer. The short answer is that we don't know why some kittens develop FCKS and some do not. It could be genetic, but it may be environmental, or it may be neither of these or a combination of both. We cannot find out the answers until we have a really significant body of data to work with, and that means gathering information from as many sources as possible.
Various causes have been suggested for the abnormal development or behaviour of the ribcage in FCKS. The Burmese Cat Club funded research into taurine deficiency which, though it only had a very small study group to work with, concluded that it was probably not relevant, although both FCKs and their littermates did show higher than usual levels of taurine. The articles originally published in the BCC News may be downloaded here and here. Other theories have suggested potassium deficiency, but treatment with potassium supplements have not shown consistently significant results in treating the condition, and blood samples have not indicated a deficiency. It is also possible that a flat chest is the end result of a variety of different disease processes so that the cause of FCKS in one breed may not be the same as in another breed. FCKS could also occur be a random congenital deformity in some cases unassociated with that kitten’s genetic make-up.
Although a variety of causes for FCKS, often implausible, have been suggested (such as queens lying on heat pads or heated floors during pregnancy), none of theses theories have been proven. It is possible that a mating with the potential to result in FCKS will have increased numbers of affected kittens associated with certain environmental conditions, but it can be clearly seen that some cats will throw FCKS and some will not, while some cats will have FC kittens in one litter, but not in another that is a repeat mating without any obvious environmental changes having been made.
Is this problem genetic?
Some lines appear to throw FCKS far more than others; virtually all studs in all breeds have thrown one at some time or another (because of the numbers of kittens they sire), so it's unavoidable, and abandoning ALL lines that have thrown FCKS would be incredibly damaging to any breed as it would limit the gene pool far too much. Having the condition manifest in a litter of kittens may rely on combinations of environment and many other factors, including the situation of the queen: any adverse event or stress during pregnancy (including poor nutrition) may render a queen more liable to produce FCKs, particularly if a litter is partially resorbed, while a less stressful environment may prevent the condition from developing. If just one flat-chested kitten appears in an otherwise normal litter then the causes could be environmental more than genetic. If a whole litter of kittens has FCKS it would be advisable not to repeat that mating, and if possible not to continue using those cats for breeding if they continue to produce kittens with the condition even when mated to other cats.
Many breeders prefer to avoid any incidence of FCKS in the lines they are using if they possibly can, even though this may severely limit their gene pool (and there are many dangers for the cat population in following this course), but sometimes a kitten will turn up in a line that was thought to be clear, showing that it can be difficult to avoid the problem completely.
Will my kittens die?
Following the development of FCKS, the outcome is unpredictable. Since onset of FCKS is fairly soon after birth, you will know quite quickly which kittens in the litter are affected and which will remain normal. A kitten may not survive the onset of the condition or it may appear to be doing well and then die suddenly at around 10 days old or thrive up to three weeks of age and then fade and die. If kittens survive beyond three weeks, then the likelihood is that they will survive to adulthood; the ribcage frequently reverts to a normal shape,(meaning that it can be impossible to distinguish a kitten that suffered with a flat chest from normal when it is an adult) or may remain flat into adulthood with no apparent side-effects. Rarely, severely affected kittens that are significantly under grown at 3 weeks will die in late kitten hood. As far as we know, a recovered FCK that is of average size and has a normal ability to exercise will have every expectation of a normal life. Similarly pectus excavatum, if severe, may compress the lungs and heart; if a PE kitten survives, it may never grow quite as large as its normal siblings.
What can I do about this?
At present, it appears most likely that FCKS is a muscular problem. A variety of treatments have been tried to relieve the kitten’s breathing difficulties and improve survival. With the exception of kittens that are gaining weight at a similar rate to normal littermates, supplementary feeding is recommended in all cases of thoracic deformity, even if the kitten appears to be feeding well, since these kittens are burning up far more energy than normal kittens just in the act of breathing (or trying to breathe). However, if the kitten fights against hand feeding or tube feeding you will have to judge whether the help given by the extra food is cancelled out by the stress and effort of struggling and the potential risk of food entering the airways rather than the oesophagus and stomach. If a kitten is hungry it will usually not fight seriously against supplementary feeding. You can help THINK to find out the cause and thereby look for prevention and cure for thoracic deformities by completing a questionnaire about your kittens, and sending it to us.
Life-saving solutions for FCKS
Breeders have saved kittens that seemed beyond help by splinting the ribcage using a cardboard or plastic tube. It is very important to be aware that if the sides of the ribcage are squeezed, this should cause the lower part of the chest to move outward, but if the sternum has already begun to collapse inwards, pressure on the sides may worsen the condition by pushing it in further instead of out. It is therefore important to understand that this procedure cannot be used with a funnel chested kitten or PE kitten, as it would push the inverted ribs further in. For this reason splinting should ideally be done under the guidance of a vet.
The first breeders to try splinting used a cardboard toilet roll, with holes cut for the front legs (which stopped it from slipping back off the ribcage). This was tied together over the kitten's back. Further refinements suggested that two flat pieces of card might have a better effect, as it would encourage the kitten to sleep on its side: as well as splinting, continually checking the kittens to make them lie on their sides may also be helpful, using gravity to help the ribcage round out correctly.
Other variations have involved using a splint made from a plastic drink bottle with tacky-bandage wrapped around it to protect the kitten's body. However it is done, splinting does seem to be a life-saving solution, with many kittens that were having breathing difficulties finding immediate relief. Work has been done in the Netherlands involving physiotherapy for 15 minutes every three hours, supported by steroid treatment. This also seems to have a good success rate, and should be investigated further. More details about treatments may be found on our website.
How can I prevent or avoid these conditions?
Don't be afraid to talk about FCKS if you have an affected litter. This is not something you caused, and it does not in any way mean you are a bad breeder, so it's nothing to be ashamed about. Only by discussing it openly will we learn more and discover why it happens. Nearly every breeder who has been breeding for some time will have experience of FCK, so even if you have not experienced it, it is worth finding out everything you can just in case.
Things to try and avoid:
Use of ANY medications including herbal and alternative remedies and food supplements during pregnancy or nursing unless they have been specifically shown to be safe, or the severity of the disease necessitates their use
Inbreeding (close line breeding), since FCK seems to appear more often in lines with limited genetic diversity.
A Queen whose kittens tend to show poor growth rates suggesting inadequate milk supply (if unavoidable, then supplement according to the kittens’ growth rates)
Breeding from a sire or queen that has had a number of litters affected with FCKS; never breed from a cat who is a recovered FCK
Poor nutrition during pregnancy and nursing: plenty of fresh, high-quality food should be available to the queen at all times.