More dog breeds found to have high risk of breathing condition

Dog owners are being warned to be cautious of a much broader range of breeds when purchasing puppies, following research showing serious breathing disorders are more prevalent than previously thought.

Dogs with a shorter snout and flatter face are known as brachycephalic breeds and have become “hugely popular” in recent years, says Francesca Tomlinson at the University of Cambridge.

But as the popularity of these breeds has soared, so too have the health issues associated with them – particularly brachycephalic obstructive airway syndrome (BOAS), easily recognisable from noisy breathing. This condition can lead to an inability to exercise, sleep and cope with heat or stress.

Concerns over BOAS have primarily focused on English bulldogs, French bulldogs and pugs. To find out which other breeds are at risk, Tomlinson and her colleagues studied 898 dogs from 14 breeds: affenpinscher, Boston terrier, boxer, cavalier King Charles spaniel, Chihuahua, Dogue de Bordeaux, Griffon Bruxellois, Japanese chin, Maltese, Pekingese, King Charles spaniel, Pomeranian, shih tzu and Staffordshire bull terrier.

All the dogs underwent respiratory testing and were subject to a range of detailed body and facial measurements.

The Pekingese and Japanese chin had the highest risk of BOAS, with over 80 per cent of dogs affected. Five breeds had a moderate risk, with BOAS seen in half to three-quarters of dogs: the cavalier King Charles spaniel, shih tzu, Griffon Bruxellois, Boston terrier and the Dogue de Bordeaux. Only among the Maltese and Pomeranian breeds did they find no dogs with clinically significant disease.

The researchers found that three main factors led to disordered breathing: being overweight, narrowing of the nostrils and extreme facial flatness. The analysis suggests that other traits, such as very short or screw tails, may also be associated with anatomical changes linked to BOAS. “This suggests that it’s not simply flatness alone that determines risk, but there are many other factors at play,” says Tomlinson.

She says prospective owners should look for puppies from parents that have undergone appropriate health testing and should educate themselves about the potential health implications of extreme bodily, especially facial, changes.

“It’s not necessarily about eliminating the defining features of a breed, but about avoiding extremes and supporting breeding decisions that prioritise function as well as appearance,” she says.

Breeders should know that it isn’t simply the breed that determines negative outcomes, she says, but the degree of exaggeration of certain physical traits. “That gives us something practical to work with – it suggests that selecting away from extremes could help to reduce disease risk.”

Anna Quain at the University of Sydney, Australia, says people don’t appreciate that a “cute” flat-faced appearance predisposes these dogs to chronic oxygen deprivation and heat stress.

Breeding dogs for flat faces is like “designing a car without a radiator”, she says. “If we are deliberately bringing dogs into the world, we should be basing those decisions on welfare first rather than preservation of a human idea of what a dog should be.”

Paul McGreevy, also at the University of Sydney, says the study confirms what most veterinarians already know. “Airway compromise is widespread among flat-faced dogs and varies considerably between and among breeds,” he says.

“For dogs struggling to excrete carbon dioxide through compromised airways, breed labels are irrelevant. Whether they are identified as a bulldog cross or registered as a Pekingese or Boston terrier is a human construct.”

However, he is concerned about some aspects of the methodology. “The assessment depends on subjective listening to breathing sounds graded by ear as mild, moderate or severe, yet provides no evidence this is being applied consistently across 14 diverse breeds,” McGreevy says. “More problematic still, the authors acknowledge their exercise test depends on individual speed capability and temperament.”

Tomlinson says the assessment incorporates objective criteria, including whether abnormal respiratory noise is audible with or without a stethoscope, and the grading follows a standardised protocol. “The aim [of the exercise test] is not to assess athletic performance, but to see how the airway responds under mild exertion,” she says.