The current worldwide popularity of different dog and cat breeds is influenced not only by personal or family preferences but also by media exposure online and in films, television, and print advertisements for pet-related products and foods. But this trend began centuries ago with the human preference for smaller, flat-faced, attractive, and charismatic brachycephalic breeds [1,2]. These breed choices continue to be popular but create a societal ethical dilemma in light of the well-known fact that brachycephalic individuals often experience acute and chronic health problems as a consequence of their anatomy and physiology [3-8]. Veterinary and animal welfare associations are taking steps to limit the showcasing of these breeds, to mitigate the unscrupulous breeding and sale of brachycephalic pets, and to increase the public’s awareness of the breeds’ problems if or when deciding to purchase such a pet [6-15]. But, are the veterinary profession, breeders and owners of brachycephalic pets, and society at large taking a strong enough stand to suspend and place a temporary moratorium on their breeding and the boycott of their purchase [8]?
Introduction
Today, the global popularity of different dog breeds is influenced not only by personal or family preferences but also by media exposure in films, television, and print advertisements for pet products, foods and treats [1,2]. These preferences continue despite the well-known fact that smaller popular brachycephalic breeds with a short nose and flat face can experience acute and chronic health problems associated with their anatomy and physiology.
The word “brachycephaly” stems from the Greek root meaning “short head” and refers to the shape of a skull being shorter than typical for its species. We find human babies so adorable with their large eyes and brachycephalic noses and faces and we love the cute cartoon characters Mickey and Minnie Mouse that differ from all known mouse or rat species.
Historically, small, short-faced dogs are one of the oldest dog types, having been carbon-dated back to as early as 10,000 years ago [1,2]. Their bones have been found in kitchen middens in the Gobi Desert, where ancient people threw their scraps and waste. Recent DNA analysis has confirmed East Asia to be the ancestral home of domestic dogs, and other studies have suggested that the Pekingese and Pug are among the oldest breeds [1,2].
Brachycephalic dog and cat breeds have been created since at least the 19th century by selective breeding for their perceived attractive features of a flat or pushed-in face and relatively large eyes. This is also known as an ‘intentional goal driven’ selection [1]. Having prize-winning purebred dogs and cats became and continues to be a societal status symbol. Further, dog breeds have evolved today from a combination of the natural evolutionary factors of type stabilization, directional intentional selection, and various disruptive/diversifying forces. The brachycephalic breeds belong to the first of these evolutionary components [2]. According to geneticist and archaeologist Greger Larson and colleagues, these breeds were purposely selected for and domesticated as long ago as 32,000 years in Eastern and Western Eurasia, near India and Nepal [2].
Although the larger and more active Labrador Retriever remains the most popular breed in North America and worldwide [3] depending upon which web site is checked, the brachycephalic French Bulldog and English Bulldog breeds rank second to fourth or fifth respectively in worldwide popularity, whereas in the United States, they rank second and fourth [3]. Many of the other 24 brachycephalic dog breeds are also very popular, including the Pug, Cavalier King Charles Spaniel, English Toy Spaniel, Shih Tzu, Boxer, Pekingese, and Boston Terrier [4-11].
For cats, among the most popular breeds are Persian, Himalayan, British Shorthair, Burmese, Exotic Shorthair, and Scottish Fold, all of which have a shortened face [12]. The recognized brachycephalic cat breeds include: Bombay, British Longhair, British Shorthair, Burmese, Burmilla, Exotic Shorthair, Himalayan, Persian, Scottish Fold, Selkirk Rex, and Silver Persian (Chinchilla Cat).
These brachycephalic dog and cat breeds are afflicted with various conformational and genetic issues that raise questions of the ethics of breeding animals with known and expected afflictions [10-15].
This two-part overview of the commonly encountered conditions in brachycephalic breeds reviews what related actions organizations have taken in this regard and emphasizes our obligation as veterinary health care professionals to seek and protect the welfare of our patients.
Table 1. Summary of clinical issues and signs in brachycephalic dogs and cats
| Clinical Issues and Signs in Brachycephalic Dogs and Cats – Literature and Websites | References |
|---|---|
| Behavior – aggression, submissiveness, depression, seizures, hyperactivity, lethargy | 8, 16 |
| Cardiovascular – bradycardia, tachycardia, arrhythmia, premature beats | 13 |
| Endocrine – especially hypothyroidism and hyper – and hypo-adrenocorticism | 8 |
| Eyes and Ears – uveitis, glaucoma, dry eye, episcleritis, tearing, corneal ulcer, ectropion, entropion, distichia; deafness, chronic otitis, ruptured tympanic membrane | 20, 25, 27 |
| Face and Mouth – temporal muscle wasting, sagging cheeks and jowls, parrot mouth, crowded dentition, gingivitis, tartar, cracked teeth, foul breath, elongated soft palate, long tongue, skin and nasal folds | 16, 19, 20, 26, 27 |
| Genetics – family and breed history | 5-9, 10, 17 |
| Limbs and Ambulation – bow-legged, arthritis and osteoarthritis, intervertebral disc disease, patellar luxation, cauda equina, cervical vertebral instability, hemivertebra, kyphosis, scoliosis, paraparesis, pelvic limb ataxia, spins bifida, urinary and fecal incontinence | 5, 7-9, 12-14 |
| Metabolic – dysbiosis, body size (weight gain or loss, obesity), anorexia, voracious appetite | 10 |
| Morbidity and Mortality – increased, reduced lifespan | 6, 8, 10, 14 |
| Neurological – seizures, tremors, ataxia, syncope, syringomyelia and Chiari-like skull malformation, hydrocephaly | 15, 19, 24 |
| Pain and Distress – internal and external | 6, 8, 14, 15 |
| Quality of Life – reduced | 6, 8, 10, 15 |
| Reproduction – impaired fertility, pseudocyesis, pyometra, reduced live litter size, mammary tumors, dystocia, requirement for C-section | 4, 5, 7-10, 13 |
| Respiratory – Brachycephalic Airway Syndrome – stertor, stridor, dyspnea, nasal discharge, exercise intolerance, gagging, regurgitation, cyanosis, hyperthermia, syncope | 6-8, 10-14, 18 |
| Skin and Haircoat – dry and scaly skin, dandruff, dry dull lifeless coat, poor coat quality, dermatitis, keratitis | 6, 8, 14, 16, 17 |
Table 2. Data from the Hemopet Laboratory Information System (LIS) from 2018-2021
| Breed | # Cases | # with Relevant Clinical Signs (%) |
|---|---|---|
| Boxer | 3,470 | 365 (10.5%) |
| English Bulldog | 3,361 | 128 (3.8%) |
| Chihuahua | 2,591 | 143 (5.5%) |
| Shih Tzu | 2,233 | 92 (4.2%) |
| French Bulldog | 1,608 | 36 (2.2%) |
| Pug | 1,531 | 78 (5.1%) |
| Yorkshire Terrier | 1,451 | 76 (5.4%) |
| Cavalier King Charles Spaniel | 1,136 | 18 (1.6%) |
| Boston Terrier | 833 | 54 (2.2%) |
| Lhasa Apso | 367 | 22 (6.0%) |
| Chow Chow | 270 | 27 (10%) |
| Bullmastiff | 237 | 5 (2.1%) |
| Pekingese | 208 | 15 (7.2%) |
| Brussels Griffon | 133 | 8 (6.0%) |
| Cane Corso | 108 | 4 (3.7%) |
| Affenpinscher | 22 | 2 (9.1%) |
| Totals | 19,523 | 1073 (5.5%) |
Anatomical Features and Clinical Issues (Tables 1 & 2 above)
Despite its rising global popularity, the French Bulldog has 20 documented common health issues [10, 12,13]. What drives the psychology behind the reason pet breeders and owners are drawn to these attractive small dogs with beguiling faces like human infants and large eyes [14]?
Respiratory Issues
The shorter skull bones and head structure that give these dogs and cats a flat face (Figures 1 & 2) also predispose them to brachycephalic airway syndrome (BAS), also called brachycephalic obstructive airway syndrome [6, 7, 12]. Stenotic nares cause many of these dogs and cats to breathe through their mouths.
Figures 1 & 2. Anatomy of a Flat-Faced French Bulldog; and Exotic Shorthair with Flat Face (with permissions)
Of the 24, 631 dogs including 2,781 French Bulldogs studied at the Royal Veterinary College in the United Kingdom, French Bulldogs were found to have an astonishing 42 times higher risk of stenotic nares [13]. Flat-faced companion animals have relatively elongated soft palates which are longer than the shortened face and mouth can accommodate, thereby extending over the epiglottis and larynx [7, 8, 13]. Their snoring usually originates here, and the stenotic nares cause excessive panting in hot weather. Suffocation and even asphyxia can occur [7, 13].
A secondary condition from the labored breathing is inflammation of the saccules of the larynx, which may cause them to become everted. The saccules can be removed surgically [8, 13]. Tracheal stenosis or hypoplasia is more commonly found in English Bulldogs and cannot be corrected surgically [8, 10].
One might think that inhaled air would travel faster to the lungs because of the shorter distance, but it is the reduced volume of air and oxygen delivered per minute that matters, as the nasal airway delivering air to the lungs is compressed and distorted. This results in the audible and irregular labored breathing commonly noted [4-10].
Due to narrowed or collapsing airway passageways, dogs with the anatomical changes and clinical issues associated with BAS are twice as likely to have anesthesia-related complications especially in the postanesthetic period [4, 13]. They also are 1.57 times more likely to have intra-anesthetic complications and 4.33 times more likely to experience post-anesthetic issues such as regurgitation, vomiting, aspiration pneumonia (most common), prolonged recovery, and stertorous breathing [4-9]. Brachycephalic dogs and cats have a higher propensity for heatstroke, hypoxia, and exercise intolerance since they must use respiration to cool down [13]. Caregivers often have a difficult time keeping weight off these pets, which then heightens their breathing difficulties [5, 7, 8].
While surgery can be performed to alleviate some of the problems and improve breathing, anesthesia poses a higher risk to these breeds because of the narrowness of their respiratory anatomy [7-10, 13-19]. Post-anesthetic care requires close observation and monitoring [14].
In 2015, a report from the United Kingdom stated that upper respiratory disorders were commonly diagnosed in the English Bulldog, French Bulldog, Pug, Border Terrier, West Highland White Terrier (WHWT) and Yorkshire Terrier dogs that were presented to primary-care veterinary practices in England [13]. The three extreme brachycephalic breed types (English Bulldog, French Bulldog and Pug) were
relatively short-lived with an average life-span of 8.6 years as compared with 12.7 years for the moderate and non-brachycephalic breed types (moderate brachycephalic Yorkshire Terrier and non-brachycephalic: Border Terrier and WHWT) [13]. After analyzing the age, weight, sex, neutering and pet insurance data, the odds for the three extreme type brachycephalic breeds having at least one upper respiratory infection was 3.5 times higher than that for the moderate and non-brachycephalic breeds [13]. A follow up article from this group confirmed and expanded these initial findings [17].
In a study from Denmark in 2017, 4 dog breeds were studied from the national Danish dog registry, namely the French Bulldog, Chihuahua, Cavalier King Charles Spaniel, and Cairn Terrier [15]. Health and other attributes of the breed were more important to owners of Cairn Terriers, whereas the personalities of the French Bulldogs and Cavaliers were more important to their owners. French Bulldogs had 14-70 times the risk of dying from respiratory problems as the other breeds [15]. Not unexpectedly, the high level of health problems in French Bulldogs negatively impacted owner intention to consider this breed again [15].
Affected brachycephalic cats may have stenotic nares, elongated soft palates, dental malalignment, everted laryngeal saccules, and hypoplastic tracheas (Figure 2) [12]. Himalayan and Persian (both the doll-face and peke-face type) cats are afflicted with similar respiratory problems and other documented health conditions because of their flat faces [24-27].
Face, Eyes, and Mouth Issues
The flattened face often leads to the eyes appearing to bulge out (exophthalmos) which predisposes to chronic eye problems [16, 20]. Since the eyelids are not long enough to cover the entire eye, the resulting dry corneal surface becomes irritated, damaged, and ulcerated. Surgical correction is required in both dogs and cats.
Heavy wrinkles of the facial folds require cleaning after every meal or at least daily to prevent skin fold eczema, yeast and bacterial infections, and malodor [4, 5, 13]. Sometimes, the proximity of the facial folds to the cornea causes the hair to poke the cornea. Overcrowded conditions in the mouth can cause the teeth to overlap or stick out at odd angles. Daily tooth brushings are critical with brachycephalic dogs or cats since food can easily get stuck and lead to tartar, periodontal disease, and abscessation [8-10, 13, 21, 22].
Limbs and Ambulation Issues
With their tendency for bowed or short legs, brachycephalic dog (many types) and cat (e. g. Munchkin, Devon Rex) breeds can have an awkward shuffling or rolling gait [5, 7-9, 13-17].
Reproduction Issues
Brachycephalic breeds have difficulty reproducing and are typically bred by artificial insemination. Problems can occur at parturition and many require a Caesarian-section delivery [4, 5, 7-10, 13].
Neurological Issues
In addition to the presence of varying degrees of congenital hydrocephalus in dome-headed brachycephalic dog and cat breeds like the Cavalier King Charles Spaniel, Persian cat, and other toy and small-breed dogs have a high incidence of Chiari-like malformation that leads to secondary syringomyelia syndrome and its painful hindbrain herniation [15, 19, 24].
Preventative Care
While many of the conditions described above are congenital and inherited, reducing the discomfort and number of veterinary and emergency care visits can be helped by 1) only using harnesses for exercise, as collars put pressure on the neck that exacerbates breathing stress and can damage the larynx or trachea, 2) giving brachycephalic breeds only controlled exercise to avoid heatstroke or heat exhaustion, and 3) maintaining a healthy weight.
References
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