Genetic welfare problems of companion animals

 

Brachycephaly

 

Breed: Persian

 

Condition:  Brachycephaly

Related terms: brachycephalic ocular disease, brachycephalic eye syndrome

Outline: Depending on its degree, the abnormal short head shape of Persian cats is associated with various disease conditions resulting in breathing difficulties, dental disease, difficulties in grooming, and irritation and ulceration of the eyes and face. These conditions can cause prolonged, recurring, discomfort and pain (which may be severe), throughout life.



 

Summary of Information

(for more information click on the links below)

 

 

1.           Brief description

The characteristics of brachycephaly in cats include a reduction in the face and skull length and a more rounded head (Künzel et al 2003). This head shape is due to an inherited defect in development of the bones of the skull (Stockard 1941).  

Schlueter et al (2009) recognised four brachycephalic head shapes in cats according to the severity of the deformity: Category I – mild; Category II – moderate; Category III - profound; and category IV – extreme (for descriptions of each see clinical and pathological effects section).


There are several serious medical conditions associated with the brachycephalic head shape in cats. These include: brachycephalic airway obstruction syndrome (BAOS) which can cause respiratory problems;
maxillary dorsorotation (rotation of the upper jaw upwards) and brachygnathism (the top jaw is abnormally short) leading to dental problems; problems with grooming; epiphora (tears running onto the face), and exophthalmos (eyeball protrusion) leading to increased risk of corneal ulcers and corneal sequestra (a dark, pigmented area on the cornea of cats, associated with chronic ulcerative or inflammatory disease of the cornea). Cats with the more severe forms of brachycephaly are most at risk from these conditions.

 

2.           Intensity of welfare impact             


In general, the more extreme the degree of brachycephaly, the greater the risk of health and associated welfare problems.

Cats affected with BAOS frequently experience breathing difficulties, which can impact on their life in a number of ways, including: discomfort, distress, disrupted sleep, restricted activity and reduced quality of life.


Dental problems due to abnormalities of the shape of the jaws can lead to discomfort and pain and the need for frequent veterinary interventions to maintain tooth and gum health.


Constant epiphora (streaming of tears on the face), caused by distortion of the tissues of the face, can cause irritation and skin inflammation, soreness and infection. Protrusion of the eyes leads to risk of corneal damage which causes pain, discomfort and irritation and may lead to partial loss of sight.

 

3.           Duration of welfare impact

 

The conditions outlined above are associated with the brachycephalic head shape, and are likely to persist or recur throughout the life of the affected individual. Surgical and/or medical treatments may alleviate some of the conditions, but are unlikely to result in complete cures.

 

4.           Number of animals affected

 

The risk of the diseases outlined above increases with the degree of brachycephaly (the degree of abnormality of head shape) and all cats with category III or IV brachycephaly are likely to have at least some of these conditions.


5.           Diagnosis

Specific diagnoses of conditions of the eye, teeth, skin and nasolacrimal drainage (tear-duct) system are made by appropriate examinations. The degree of brachycephaly can be assessed using Schlueter et al’s (2009) categorisations.

 

6.           Genetics

 

The brachycephalic head shape defect has a clear genetic basis, and has been selected for in some breeds and not others. However, the genes involved are unknown.

This inherited defect is a defining character of all brachycephalic breeds of cat. Some lines of Persians have been bred for even more pronounced and exaggerated brachycephalic features, eg large, round eyes, domed cranium and lack of nasal bones. These ‘ultra-Persians’ have category III and IV skull shapes. The health and welfare problems tend to be greatest in these most severe brachycephalic forms.

 

 

7.           How do you know if an animal is a carrier or likely to become affected?

Brachycephalic parents tend to produce brachycephalic offspring and brachycephalic kittens grow into brachycephalic adults. There is therefore little difficulty in observing which animals are affected. The health and welfare problems associated with this head shape would be eliminated if there was no demand for animals with brachycephalic head shapes. For welfare reasons, therefore, it would be better if prospective pet owners chose only cats with natural head shapes.


8.          Methods and prospects for elimination of the problem

 

The health and welfare problems associated with brachycepahly could be reducedby not breeding from animals with abnormal head shapes. It is likely that they could also be addressed (although with less rapid benefit) by out-crossing Persians with other breeds (with more natural head shapes)  , although some may question the ethics of breeding animals that may be at serious risk of health and welfare problems because of their conformation.  Because of the health and welfare risks, it would appear to be better not to show, breed, or permit registration of brachycephalic Persian cats.

 

 


 

For further details about this condition, please click on the following:

 

 

 

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1.           Clinical and pathological effects

 

The characteristics of brachycephaly include a reduction in the face and skull length of an affected individual and a more rounded, ‘doming’ of their skull (Künzel et al 2003). This head shape is due to an inherited defect in development of the bones of the skull (Stockard 1941), where the bones that form the jaw/muzzle grow more slowly than the other bones of the head. The reduction in the size of the face, due to the abnormal bone growth, is not accompanied by a corresponding reduction in the size of the soft tissues of the head. Hence, externally, the skin of the face tends to be thrown in folds and, internally, the mucous membrane linings of the nose and airways are disproportionately large.

A recent study (Schluter et al 2009) has classified brachycephalic head shapes in cats into 4 categories according to the severity of their deformity

 

  • Category I: Mild brachycephaly, shows as near vertically positioned upper canine teeth without dorsorotation of the upper jaw, “an inconspicuous stop, and clearly developed facial and neurocranial bones”. (The stop is the bend at the junctions of the nasal and frontal bones, between the nose and the face; dorsorotation means that the plane of the upper jaw is tilted vertically so that the angle towards the backbone narrows.)
  • Category II: Moderate brachycephaly, “which is characterised by an incipient dorsorotation of the canine teeth and upper jaw in a dorsal (upwards) direction, a distinct stop, reduced facial bones and a rounded or even apple-shaped cranium (the part of the skull that houses the brain).
  • Category III: Profound brachycephaly, in which “a pronounced rotation of the upper jaw and canine teeth was obvious. Additionally these cats showed a distinct stop with reduced facial and neurocranial bones. Because of the dorsorotated upper jaw, the tip of the nose is at a higher level than the lower eyelid”.
  • Category IV: Severe: The upper canines are nearly in a horizontal position and there is a high level of dorsorotation of the upper jaw. “An overly pronounced stop, underdeveloped facial bones and a rounded cranium” are present. (Schlueter et al 2009, p892).


Cats with category III or IV brachycephaly have been called ‘ultra-Persians’.

There are several serious medical conditions associated with the brachycephalic head shape in cats, as outlined below. These include: brachycephalic airway obstruction syndrome (BAOS) which can cause respiratory problems; maxillary dorsorotation (rotation of the upper jaw upwards) and brachygnathism (the top jaw is abnormally short) leading to dental problems; problems with grooming; epiphora (tears running onto the face), and exophthalmos (eyeball protrusion) leading to increased risk of corneal ulcers and corneal sequestra (a dark, pigmented area on the cornea of cats, especially Persians, associated with chronic ulcerative or inflammatory disease of the cornea). Cats with the more severe forms of brachycephaly are most at risk from these conditions.

 

  • Brachycephalic airway obstruction syndrome (BAOS). One of the common abnormalities associated with BAOS in the Persian cat is stenotic nares (abnormally narrow nostrils, (Monnet 2004, Brown and Gregory 2005)). This is usually a bilateral condition (that affects both nostrils), which causes partial occlusion of the airway (blockage), and by so doing increases the effort needed for breathing. In addition, Ginn et al (2008) found that 20% of the brachycephalic cats they examined had abnormally positioned nasal turbinates (the scroll-like bones of the nose) in the nasopharynx (the part of the throat behind the nose), which is also likely to distort nasal passages and cause some respiratory occlusion (Hendricks 1995). 
 

Schlueter et al (2009) showed that the greater the distortion of the skull the narrower the nostrils, nasal airways and nasal cavity. In cats with category III and IV brachycephaly, the permanent narrowing and obstruction of the airways is likely to make breathing much harder resulting in snoring, respiratory noise, and mouth breathing.

  • Dental problems.Due to the dorsorotation of the upper jaw in cats with category III and IV brachycephaly, the teeth erupt at abnormal angles. The canine teeth often protrude almost horizontally from the mouth. Affected animals have problems eating and chewing food, and food remains build up on the teeth leading to an increased rate of plaque and calculus formation and periodontal disease (Malik et al 2009). Canine teeth are also important for grooming and the abnormal position of these canines add to the grooming difficulties experienced by many long-haired cats. Affected animals may show signs of eating difficulties or perhaps reluctance to eat, and may have matted coats.
  • Epiphora (the presence of tears running onto the face). Epiphora occurs in Persians with more severe brachycephaly due to distortion and kinking of the fine ducts that normally drain the tears from the eyes into the nasal passages. Because of this, the ducts do not drain away the tears adequately and they constantly overflow onto the face. Schlueter et al (2009) showed that in severely brachycephalic cats the tear duct has to take a tortuous path, that takes it below the level of the upper canine tooth, due to the dorsorotation of the upper jaw. They also found that in category III and IV cases the lacrimal puncta (the openings of the tear ducts at the inside corner of each lower eyelid) are lower than the ducts’ openings at their other end, which are within the nose. This difference means that for tears to pass through the ducts, the tears would actually have to flow against gravity. The constant wetness, caused by the overflowing tears, stains the fur between the eyes and nose of these cats, and predisposes affected cats to skin infections  and  dermatitis (inflammation of the skin) (Morgan 2007), with accompanying  soreness, and ulceration.
 

An idiopathic facial dermatitis has been reported in Persians which could be a separate genetic condition of the breed, or which may be due to epiphora caused by brachycephaly as described above. In this condition there is itchiness, redness (erythema) and excoriation of the skin (trauma due to scratching) (Bond et al 2000).

  • Entropion. This is where the eyelid rotates inwards such that the hairs on the outer surface of the eyelid are brought into contact with, and constantly rub on, the cornea (the clear surface of the eye). This causes chronic irritation and may lead to ulceration of the cornea (see below). Persians are predisposed to this condition due to their facial anatomy (Williams and Kim 2009).
  • Exposure keratopathy, and corneal ulceration and corneal sequestra. The comparatively shallow orbits associated with brachycephaly makes the eyes more protuberant and and increases the chance that they may suffer corneal damage (although this is much more common in brachycephalic dogs than cats) (Hartley 2010) and exposure keratopathy (see below) (Slatter 2001). Like brachycephalic dogs, brachycephalic cats also show decreased corneal sensitivity compared to normal cats (Hartley 2010). This may also be a factor in making their eyes more vulnerable to damage, as, for example, this may make them less responsive to the presence of irritants that cause damage the surface of the eye, which in unaffected cats would be otherwise quickly washed away by blinking and/or tear production
 

Exposure keratopathy (chronic inflammation due to the relative over-exposure of the cornea) can lead to increased risk of infection, erosion of the surface layer of the cornea and ulceration (where deeper layers of the eyeball are eroded too (Startup 1984, Renwick 1996). Ulcers in the cornea can deepen until they cause rupture of the eyeball. Deep corneal ulcers or ruptured eyes are veterinary emergencies. Eye rupture may necessitate the surgical removal of the eye.

 

Chronic irritation of the eyes,  rom entropion, or nasal fold trichiasis, in which folds of skin on the shortened nose come into contact and rub on the cornea, also increases the risk of corneal ulceration in the Persian (Slatter 2001). Additionally, brachycephalic cats are predisposed to developing ulcers that fail to heal following routine veterinary treatments. A third of the cats in a study of non-healing ulcers were Persians (La Croix et al 2001).

 

Persians are also predisposed to a condition called corneal sequestra (also called corneal nigrum, corneal mummification, and corneal necrosis). These sequestra are areas of dead corneal cells which appear like a dark pigmented patch on the eye surface (Hartley 2010). In a study by Featherstone and Sansom (2004), Persians were found to be the breed of cat most commonly affected by this condition. Corneal sequestra are caused by any chronic irritation to the eye (Sapienza 2002). 

 

Cats with these chronic eye problems may rub at their faces and eyes, hold their eyes partially closed (due to increased sensitivity to light), and show increased frequencies of blinking (all of which are signs of discomfort or pain). There may be discharges from the eyes, and the surfaces of the corneas may be abnormal and show pigmentation, clouding, and irregularity. Sight is affected when there is corneal scarring.

There are medical and surgical approaches for treating entropion, nasal fold trichiasis, corneal ulceration and corneal sequestra, but it may not be possible to prevent recurrence of sequestra or ulceration. Stenotic nostrils can be surgically enlarged, but narrowing of other nasal passages and the  jaw and teeth abnormalities and epiphora outlined above, cannot be changed.

 

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2.               Intensity of welfare impact

In general, the more extreme the degree of brachycephaly, the greater the risk of health and associated welfare problems.

Cats affected with BAOS frequently experience breathing difficulties, which can impact on their life in a number of ways, including: discomfort, distress, disrupted sleep, restricted activity and reduced quality of life.


Dental problems due to abnormalities of the shape of the jaws can lead to discomfort and pain and the need for veterinary interventions to maintain tooth and gum health.


Constant epiphora (streaming of tears on the face), caused by distortion of the facial tissues, can cause irritation and skin inflammation, soreness and infection. Protrusion of the eyes leads to an increased risk of corneal damage; damage which can cause pain, discomfort and irritation and may lead to partial loss of sight. Entropion also causes chronic irritation and pain.


The extent that an individual is affected by these conditions will depend on the severity of their brachycephaply as will the discomfort and pain they experience, which may be severe. When they occur together, as they often do in severely brachycephalic cats, it seems reasonable to conclude that they have a significantly detrimental impact on an individual’s quality of life.

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3.           Duration of welfare impact

 

The disease conditions outlined above are associated with the brachycephalic head shape, and are likely to persist or recur throughout life. Surgical and/or medical treatments may alleviate some of the conditions, but are unlikely to result in complete cures.

 

Return to top

 

4.           Number of animals affected

 

The risk of the diseases associated with brachycephaly, as outlined above, increases with the degree of brachycephaly (the degree of abnormality of head shape) and all cats with category III or IV brachycephaly are likely to have at least some of these conditions.



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5.           Diagnosis

 

Specific diagnoses of conditions of the eye, teeth, skin and nasolacrimal drainage (tear-duct) system are made by appropriate examinations. The degree of brachycephaly can be assessed using Schlueter et al’s (2009) categorisations.

 

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6.           Genetics

Recently the region of the canine genome associated with brachycephaly in dogs has been identified and two particular genes have been implicated (Bannasch et al 2010). However, the genes involved in brachycephaly in cats are currently unknown.

This inherited defect is a defining character of all brachycephalic breeds of cat. Some lines of Persians have been bred for even more pronounced and exaggerated brachycephalic features, eg large, round eyes, domed cranium and lack of nasal bones. These ‘ultra-Persians’ have category III and IV skull shapes. The health and welfare problems tend to be greatest in these most severe brachycephalic forms.

 

Return to top

 

7.           How do you know if an animal is a carrier or likely to become affected?

Brachycephalic parents tend to produce brachycephalic offspring and brachycephalic kittens grow into brachycephalic adults. There is therefore little difficulty in observing which animals are affected. The health and welfare problems associated with this head shape would be eliminated if there was no demand for animals with brachycephalic head shapes. For welfare reasons, therefore, it would be better if prospective pet owners chose only cats with natural head shapes.

Return to top

 

 

8.          Methods and prospects for elimination of the problem

These health and welfare problems associated with brachycephaly could be reduced by not breeding from animals with abnormal head shapes. It is likely that they could also be addressed (although with less rapid benefit) by out-crossing Persians with other breeds (with more natural head shapes). Although, some may question the ethics of breeding animals that may be at serious risk of health and welfare problems because of their conformation. 

Schlueter et al (2009) recommended that cats with profound or extreme brachycephaly (categories III or IV), should not be used for breeding and that preference should be given to cats with more extensive facial bones, lack of dorsorotation of the upper jaw and an inconspicuous facial “stop”. They suggested that breeders and show judges could use the angle of the canine teeth as a method to help assess the degree of dorsorotation of the upper jaw. They noted that in Germany there is already a ban on breeding cats whose nose tip is higher than the level of the lower eyelid.

Malik et al (2009), in an editorial in the Journal of  Feline Medicine, called for banning these extreme brachycephalic phenotypes (as also did the Feline Advisory Bureau) and voiced concerns that continued breeding of extreme brachycephalic cats might lead to the emergence of further significant welfare problems.


It would seem relatively easy for cat breeding governing bodies around the world to adopt a policy of banning registration, showing and breeding of cats that fall within Schlueter et als’ (2009) profound or extreme categories

 
 

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9.          Acknowledgements

UFAW is grateful to Rosie Godfrey BVetMed MRCVS and David Godfrey BVetMed FRCVS for their work in compiling this section.

 

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10.          References


Bond R, Curtis CF, Ferguson EA, Mason I and Rest J (2000) An idiopathic facial dermatitis of Persian cats. Veterinary Dermatology 11: 35-41

Brown D and Gregory S (2005) Brachycephalic Airway Disease. In: BSAVA Manual of Canine and Feline Head, Neck and Thoracic Surgery. Editors, D. Brockman and D. Holt. British Small Animal Veterinary Association, Cheltenham pp 84

 

Featherstone H and Sansom J (2004) Feline corneal sequestra: a review of 64 cases (80 eyes) from 1993 to 2000. Veterinary Ophthalmology 7: 213-227

 

Ginn JA, Kumar MSA, McKiernan BC and Powers BE (2008) Nasopharyngeal Turbinates in Brachycephalic Dogs and Cats. Journal of the American Animal Hospital Association 44: 243-249

Hartley C (2010) Aetiology of corneal ulcers. Journal of Feline Medicine and Surgery 12: 24-35


Hendricks J (1995) Recognition and treatment of congenital respiratory tract defects in brachycephalics. In: Kirk’s Current Veterinary Therapy XII small animal practice edited by J. Bonagura.
Philadelphia: W.B. Saunders pp 892

 

Künzel W, Breit S and Oppel M (2003) Morphometric investigations of breed-specific features in feline skulls and considerations on their functional implications. Anatomia, Histologia, Embryologia 32: 223


La Croix NC
, van der Woerdt A and Olivero DK (2001) Nonhealing corneal ulcers in cats: 29 cases (1991-1999). Journal of the American Veterinary Medical Association 218: 733-5

Malik R, Sparkes A and Bessant C (2009) Brachycephalia – A bastardisation of what makes cats special. Editorial. Journal of Feline Medicine and Surgery 11: 889-890


Monnet E (2004)
Brachycephalic Airway Syndrome. World Small Animal Veterinary Association conference 2004, 6-9th Oct, Rhodes, Greece. Available from VIN Associate, accessed 8.2.11


Morgan R (2007) Epiphora. Available from VIN Associate. Accessed 7.2.11

 

Renwick P (1996) Diagnosis and treatment of corneal diseases in dogs. In Practice 18: 315-328


Sapienza J (2002) Corneal Diseases of Dogs and Cats. World Small Animal Veterinary Association conference 2002 proceedings. Available from VIN Associate. Accessed 8.2.11

Schlueter C, Budras K, Lugewid E, Mayrhofer E, Koenig H. Walter A and Oechtering G (2009) Brachycephalic feline noses: CT and anatomical study of the relationship between head conformation and the nasolacrimal drainage system. Journal of Feline Medicine and Surgery 11: 891-900

Slatter D ( 2001) Fundamentals of veterinary ophthalmology. 3rd Ed, Saunders: Philadelphia, USA. pp 280

Startup F (1984) Corneal ulceration in the dog. Journal of Small Animal Practice 25: 737-752

 

Stockard (1941) Wistar Institute Monograph. The genetic and endocrine basis for differences in form and behaviour as elucidated by studies of contrasted pure line dog breeds and their hybrids. Animal Anatomical Memoirs No 19, The Wistar Institute. 1-146

 

Williams D and Kim J (2009) Feline entropion: a case series of 50 affected animals (2003-2008). Veterinary Ophthalmology 12: 221-6

 

 

© UFAW 2011

 

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