The Scottish Fold breed of cat has a very distinctive appearance and is a popular companion cat in some countries. These cats have flattened ears that fold forward and downward, sitting like a cap and giving the quaint look of an owl. This ear fold is the result of a natural genetic mutation first observed in a farm kitten in Scotland in 1961. The genetic mutation which causes the folded ears has now been identified and is a single gene variant in TRPV4, which impacts the development of cartilage.
The tightly folded ears do not appear to be any more prone to infections than those of cats with upright ears. However, this unique ear shape is caused by an underlying defect in the formation of cartilage, which would normally retain the ears in a normal shape.
This inherited cartilage defect (also known as Scottish Fold Osteochondrodysplasia or Scottish Fold disease) causes other deformities throughout the body and is a dominant trait, meaning all kittens with the TRPV4 variant gene will be affected. All kittens born to two Scottish Fold parents with two copies of the gene variant will be affected by Scottish Fold Osteochondrodysplasia. Half of the kittens in a litter from a cross between a Scottish Fold and another breed or two Scottish Folds with one copy of the gene variant will be affected with Scottish Fold Osteochondrodysplasia to some degree.
The disease is evident on x-rays of cats from as young as seven weeks of age. Serious abnormalities in joints and bone growth lead to arthritis (painful, swollen joints), short, abnormally thick, and inflexible tails, spinal abnormalities and short, stiff legs. The welfare impacts of Scottish Fold Osteochondrodysplasia can be severe in terms of pain and inability to perform natural behaviours, as these cats can be lame, walk with an abnormal gait, can be reluctant to engage in normal movements such as walking or jumping, and can even become completely crippled.
There is no cure for this progressive condition. Cats who develop arthritis need long term pain relief, which can have undesirable side effects, and dietary supplements to try and slow its development. In a small number of cases, surgery or radiotherapy has been effective in slowing the progression of the disease. Those with severe disease are often suffering immensely and require euthanasia, sometimes early in life.
Due to the crippling deformities evident in this breed, it was excluded from the Cat Fancy of Great Britain as a recognised breed in 1974 and was also banned by the Fédération Internationale Féline. Breeders in the USA persisted, however, and have attempted to improve the health of the breed by never breeding Scottish Folds together but instead, crossing them with either American Shorthairs or British Shorthairs. Now that cats can be tested for the gene variant that causes the folded ears and Scottish Fold Osteochondrodysplasia, some breeding programs will breed Scottish Folds who have just one copy of the gene to produce a mixed litter where half of the offspring will carry the folded-ear gene TRPV4 variant – these kittens have the folded ears while the other kittens do not have the TRPV4 variant gene and have straight ears and are sometimes called ‘Scottish short-hairs’.
The kittens who have just one copy of the gene TRPV4 variant (and folded ears) have been shown to develop Scottish Fold Osteochondrodysplasia of varying severity.
It was once thought that the ear fold was the only impact on cross-bred Scottish Folds but in the early 1990s, Australian veterinary researchers proved that all cats with the ear fold will develop the painful effects of osteochondrodysplasia to varying degrees. The visual deformities are less severe in cross-bred cats and the resulting arthritis may be milder or slower to progress in some, but others still suffer from significant disease from as early as six months of age. Euthanasia on welfare grounds may be required.
This condition is preventable by not breeding from any cats with folded ears. All Scottish Fold cats with folded ears are affected by this disease. Scottish Fold cats continue to be bred in the USA, Australia, and Asia, with marketing focusing on the quality of the ear fold.
The RSPCA believes it is unethical to breed from animals with a genetic mutation that is known to cause painful deformities and disease. It is important to realise that the folded ears many find ‘cute’ in Scottish Fold cats, are highly unnatural for the animals themselves (the result of a random and unfortunate mutation) and that the underlying condition responsible for this appearance has profound detrimental effects on their welfare. Since the only ‘benefit’ of having the TRPV4 variant gene is the folded ear look that some people find appealing, the RSPCA does not support breeding Scottish Fold cats, including breeding a Scottish Fold with a cat without folded ears given the risk of at least some kittens being affected even in litters from mixed parents,
Affected Scottish Fold cats cannot be bred in Victoria under The Prevention of Cruelty to Animals Act 1986 – Code of Practice for the Breeding of Animals with Heritable Defects that Cause Disease.
What can owners of Scottish Fold cats do to help their pets?
Scottish Fold cats may require specialised veterinary care to help them to be more comfortable and to improve their quality of life. These cats may also need ongoing extra daily care from their owners in addition to general care needs. Potential owners who have busy lifestyles or limited income should carefully consider their capacity to provide adequate care should this be required.
If you own a Scottish Fold cat, you can help your pet in a number of ways:
- Be fully aware of the Scottish Fold specific health and welfare problems.
- Talk to your veterinarian about what you need to be aware of and what you can do to help your cat.
- Help ensure the Scottish Fold specific health and welfare problems are not passed on to future generations by getting your cat desexed. Cats’ health and welfare should be considered as a priority over appearance in making breeding decisions.
1. Takanosu M, Takanosu T, Suzuki H, Suzuki K (2008) Incomplete dominant osteochondrodysplasia in heterozygous Scottish Fold cats: Case Report. Journal of Small Animal Practice 49:197–199
2. Rorden C, Griswold MC, Moses N, Berry CR, Keller GG, Rivas R, Flores-Smith H, Shaffer LG, Malik R (2021) Radiographical Survey of Osteochondrodysplasia in Scottish Fold Cats caused by the TRPV4 gene variant. Hum Genet 140:1525–1534