The diversity of dog breeds is a fascinating phenomenon that illustrates the human ability to shape nature to meet our aesthetic needs and preferences. However, this diversity comes at a cost: a significant increase in the prevalence of certain genetic diseases in pure dog breeds.
Genetic selection: the method and its consequences
Genetic selection in dogs is a practice that aims to preserve or reinforce certain specific characteristics of a breed. It is generally carried out by promoting the breeding of dogs that have these characteristics, often through consanguineous breeding.
According to a 2016 study published in “The Veterinary Journal,” genetic selection can increase the prevalence of hereditary diseases among a purebred dog population. The study looked at 10 dog breeds and found that the prevalence of hereditary diseases was significantly higher in purebred dogs than in crossbred dogs.
The numbers: a worrying increase
In a 2020 study published in “Canine Genetics and Epidemiology,” researchers analyzed more than 50,000 veterinary records and found that over 60% of purebred dogs carried at least one genetic mutation linked to a disease. For example, hip dysplasia, which can cause severe pain and mobility difficulties, was observed in around 20% of Golden Retrievers and 30% of English Bulldogs examined in the study.
Additionally, a 2019 study published in “The Journal of Veterinary Internal Medicine” found that the prevalence of certain heart conditions, such as aortic stenosis, was 10 times higher in Boxers than in mixed breed dogs. Additionally, the same study showed that Cavalier King Charles Spaniel breed dogs were 20 times more likely to develop mitral heart disease than other dogs.
Specific breeds, specific problems
Some breeds are particularly affected by specific health problems due to genetic selection. For example, Bulldogs and Pugs, selected for their flat faces and short noses (a trait called brachycephaly), often suffer from breathing problems. A 2018 study published in “PLOS ONE” showed that over 80% of Pugs, French Bulldogs, and English Bulldogs suffer from some forms of brachycephalic breathing disorders.
The lower back end of German Shepherds became a desired trait because of its distinctive appearance and the idea that it could improve the dog's performance when it came to work or show. The breeders who promoted this trait did so in order to meet the aesthetic standards of the breed or to strengthen certain physical abilities. However, the unintended consequence of this selection has been an increase in health problems associated with this particular body structure.
The unusual structure of the German Shepherd's hindquarters has been associated with an increased incidence of hip dysplasia and spine problems. Hip dysplasia is a hip joint defect that can lead to arthritis and chronic pain. According to a study by the Orthopedic Foundation for Animals (OFA) carried out in 2010, around 20% of German Shepherds are affected by this disease.
Low hindquarters can also cause excessive strain on a dog's spine, which can lead to back problems. A 2017 study published in the “Journal of Small Animal Practice” found that German Shepherds are more likely to develop degenerative intervertebral disc disease, a painful condition that can limit a dog's mobility.
Additionally, the Dachshund breed, or dachshund, is known for its long backbone and short legs. However, these characteristics increase their risk of developing back problems, such as intervertebral disc disease. According to a study published in 2016 in the “Journal of Small Animal Practice,” around 20% of Dachshunds will develop this condition during their lifetime.
The Scottish Terrier, on the other hand, has a high prevalence of bladder cancer. A study published in the “Journal of Veterinary Internal Medicine” in 2011 showed that this breed is 20 times more likely to develop bladder cancer than other breeds.
Efforts to improve the health of purebred dogs
Faced with these alarming figures, researchers, breeders and canine organizations are working to find solutions. One way to do this is to reduce the degree of consanguinity in purebred dog breeding. Increasing genetic diversity within a breed can help reduce the prevalence of certain hereditary diseases.
Genetic tests are also increasingly being used to identify carriers of genetic mutations prior to reproduction. Many responsible breeders use these tests to make sure they don't unintentionally spread genetic diseases.
Additionally, some dog organizations, like the Kennel Club in the United Kingdom, have begun to change breed standards to promote healthier traits. For example, the Kennel Club changed its standard for the English Bulldog in 2009 to encourage a longer face and fewer wrinkles, in an effort to reduce respiratory problems.
Genetic selection in purebred dogs has led to a significant increase in the prevalence of certain hereditary diseases. However, thanks to a better understanding of canine genetics and the commitment of responsible breeders, steps are being taken to improve the health of these dogs. By continuing to value genetic diversity and re-evaluating breed standards, we can hope to reduce the impact of these diseases on our four-legged friends.
