Scottish Fold: genetic diseases

2023 Author: Alex Livingston | [email protected]. Last modified: 2023-11-26 11:39

Attempts to select the breed Scottish Fold initially caused the presence of genetic diseases in born puppies. How was this possible?

In 1961 at the McRae farm in Scotland, a small white cat named Susie was born: a spontaneous mutation had caused the pavilions of her ears to be folded forward and close to her head, making her look like an owl. When Susie had her first puppies, some of them were born with the same folded ears as their mother.

This striking peculiarity was noticed by the spouses William and Mary Ross, both passionate about cats, who adopted one calling it Snooks. The cat was crossed by William with a British Shorthair and it was discovered that the folded ears they were a character that was passed on from parents to children. The spouses understood that in all probability the folded ear was a genetically dominant trait.

The Rosses thus began a breeding program and in 1966 registered their cats as the Scottish Fold with the Governing Council of the Cat Fancy, the UK herd registry. However, the first crosses did not give the desired results since the folded ear gene was associated with physical and joint problems. It was soon discovered, in fact, that if the Scottish cats were mated with each other, many of the kittens developed a series of serious diseases.

First of all, the onset of ear parasitosis associated with a high percentage of deafness; these ear diseases were prevented simply with thorough cleaning. What worried, however, was that the gene responsible for the mutation of the ears was also a carrier of osteodystrophy, or serious problems in the joints, for which the kittens presented a severe and disabling limp at the beginning of their life. The cats so affected had short, malformed legs and radiographic anomalies, the vertebrae of the tail welded together and the joints of the legs became covered with cartilage, preventing their movement.

Mary Ross in 1971 sent three Scottish Fold kittens to a research center in Massachusetts for a study of their mutations. Geneticist Neil Todd understood that for a good selection that could lead to the birth of cats with folded ears, but which were also healthy, mating had to always take place with straight-eared cats as the gene responsible for the folding of the auricles is a autosomal dominant mutant gene Fd: its presence in only one of the parents is sufficient to be transmitted to the offspring. The cats were no longer crossed only with each other Scottish Fold but with different breeds. Within a few years the breed was therefore officially recognized and to date the authorized mating is only with British Shorthair and American Shorthair.

With the selection that has led to the definition of the Scottish Fold breed it is natural that not all puppies in a litter will have the characteristic folded ears. To understand which of them have recovered the gene it is necessary to wait at least fifteen to twenty days from their birth, since only then will the kittens begin to have the ear cartilage crinkled so that only the tip can bend forward.

The Scottish Fold cat, contrary to what many believe, today looks like a long-lived breed that can live up to fifteen years of age and, thanks to a correct selection, turns out to be a healthy and robust cat. However, there are cat breeds such as the Scottish Fold which, due to the aforementioned genetic mutations, are more prone than others to develop diseases.

Polycystic Kidney Disease (PKD), or disease of the polycystic kidney. In this pathology, cysts develop in the renal cortex and medulla oblongata, increasing in size and number with the age of the cat to the point of causing kidney failure. The latter manifests itself differently from cat to cat. Cysts usually grow very slowly, and felines show no signs of the disease until later in life, typically around the age of eight.

Familial hypertrophic cardiomyopathy (HCM), that is, thickening of the heart muscle resulting in a reduction in the volume within the ventricles (main chambers of the heart) of the blood that the heart can pump with each contraction. The affected animal is at risk of developing heart failure congestive and occasionally sudden death.

Scottish fold osteochondrodysplasia (SFOCD), that is to say skeletal anomalies. Due to this disease, the cartilages do not grow strong enough to support the ears as they normally do. The pathology does not only concern the ear cartilages, but also other bones. These abnormalities present lameness, stiffness and reluctance to jump in affected cats.

Finally, the particular shape of the ears of this Scottish Fold cat requires more attention and one daily cleaning to avoid annoying ear parasites due to excessive accumulation of dirt.