Chihuahuas are at risk of the same breathing difficulties as pugs, a study has shown.
Between 25-50 per cent of the archetypal handbag dogs, once sported as accessories by celebrities including Paris Hilton, display symptoms of Brachycephalic Obstructive Airway Syndrome (BOAS), commonly diagnosed in pugs, bulldogs and French bulldogs.
The condition, which causes the dogs to wheeze and overheat when exercising, can significantly shorten their lifespan. It is well-documented in flat-faced dogs, leading to calls to ban those with extreme traits from being bred.
According to a University of Cambridge study, a further 12 breeds of canines, many of which are “designer dogs”, may be at risk of the same breathing problems.
The small breeds highlighted by the researchers included Chihuahuas, Shih Tzus, Brussels Griffon and Pekingese.
A number of large dog breeds, including boxers and Dogue de Bordeaux, were also graded as at risk of difficulties.
Researchers at the Cambridge Veterinary School assessed 14 breeds and graded them for BOAS on a scale of zero to three, with zero indicating few symptoms and three meaning the animal had difficulty exercising and inhaling enough air.
Dr Fran Tomlinson, the study co-leader, said BOAS can “significantly reduce quality of life” and lead to “serious welfare issues”.
Across a total of 898 dogs, the study showed that 12 out of the 14 breeds had a detectable level of breathing abnormality.
Pekingese and Japanese Chin were found to have a BOAS rate similar to bulldogs, with 89 per cent and 82 per cent of the dogs affected, respectively.
Both of these breeds are required under Kennel Club standards to have short muzzles, with a wrinkled face desired for the Pekingese.
While flat faces are widely understood to lead to breathing problems, researchers said the study sheds new light on the extent to which shortened muzzles may be to blame.
For King Charles Spaniels, Shih Tzus and Boston Terriers, between 50 and 75 per cent experienced some breathing issues.
Meanwhile, among Cavalier King Charles Spaniels, Pomeranians, Boxers and Chihuahuas, between 25 and 50 per cent had breathing difficulties.
None of the Pomeranian or Maltese dogs studied were found to be clinically affected.
The results come amid calls to restrict the breeding of “designer dogs” that have certain endearing physical attributes. Some of these purposefully bred characteristics can lead to them suffering from health problems, including flat faces, wrinkly skin and bulging eyes.
The trend of using a dog as an accessory was popularised by Hilton in the early 2000s, when she owned a Chihuahua called Tinkerbell that she carried in her handbag.
The rise of social media and wealth of influencers sharing images of their handbag dogs has also prompted a high demand for the breeds, with some Pekingese puppies selling for thousands of pounds.
To give the dogs a BOAS score, researchers adapted the Kennel Club’s respiratory function grading scheme, used to assess French bulldogs, bulldogs and pugs, to measure the breathing difficulties of the 14 additional breeds.
The team assessed the dogs’ breathing before and after a three-minute exercise test, grading any upper respiratory noises and signs of difficulty or discomfort.
In BOAS, lesions within the upper respiratory tract result in narrowing of the airway, which often leads to noisy breathing but can also reduce a dog’s ability to exercise, sleep and cope with heat or stress.
Dogs that completed the exercise test with no breathing discomfort or respiratory noise were classified as unaffected, while dogs that displayed any upper airway noises were classified from mild to severe BOAS.
According to the study, published in the journal PLOS One, dogs which are overweight or have narrowed nostrils or a wider, shorter head shape are more likely to suffer from BOAS.
In some breeds, the research team found that shorter tails and thicker necks are an additional risk factor.
Last year, the Kennel Club banned dogs with moderate or severe breathing difficulties from competing at Crufts in a move designed to reduce the animals’ suffering.
Responding to the study, the Kennel Club announced the expansion of its grading scheme to include the 14 dog breeds tested.
The scheme enables owners to have their dogs tested for BOAS and advises breeders on how to lower the risk of producing affected puppies.