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Genetic Welfare Problems of Companion Animals
An information resource for prospective pet owners
Shar Pei
Entropion
Related terms: In-turning of the eyelids, conformational entropion, developmental entropion.
Outline: Entropion is a deformity of the eyelids, common in Shar pei, such that the outer edge of the eyelid turns inwards resulting in the eyelashes constantly rubbing on the surface of the eye causing irritation, discomfort, chronic abrasion and pain. The condition predisposes affected individuals to forms of chronic conjunctivitis causing episodes of varying degrees of discomfort and pain throughout their lives unless eyelid conformation can be surgically corrected (which may be difficult). Animals should be chosen as pets or for breeding only if they have normal eyelid conformation or these diseases are likely to be perpetuated.
Summary of Information
(for more information click on the links below)
1. Brief description
Entropion is a deformity of the eyelids, common in Shar pei, such that the outer edge of the eyelid turns inwards resulting in the eyelashes, skin and fur of the outer surface of the eyelid constantly rubbing on the surface of the eye causing discomfort and pain.
The irritation that is the result of the surface of the eye coming into repeated contact with facial hairs and eyelashes leads to increased tear production, conjunctivitis (inflammation of the conjunctiva -the tissues lining the eyelids), keratitis (inflammation of the cornea -the clear front surface of the eye) and abrasion and ulceration of the cornea. Affected animals may hold the eye shut (blepharospasm) and show signs of photophobia (sensitivity to light) because of the pain. There may be corneal opacity and vascularisation – growth of blood vessels across the surface of the eyeball - both of which can permanently affect vision, and ocular discharge.
2. Intensity of welfare impact
This can vary from mild to severe depending on the severity of the facial and eyelid abnormalities present. Affected dogs are likely to suffer from constant irritation, discomfort and pain which may be severe, especially at times when eye tissues are infected. If the disease processes progresses, vision can become permanently impaired; with blindness due to keeping the affected eye shut or due to scarring of the surface of the eye seen.
3. Duration of welfare impact
The condition, and the distress and pain it causes, are potentially life long, often starting soon after the affected pups eyes open at two weeks of age (Bedford 1988, Yaphé 2005). During their life, individuals may suffer episodes of greater severity associated with periods of infection.
4. Number of animals affected
The proportion of animals affected has not been reported as far as we are aware; however, one large study in the USA suggested Shar pei are 131 times more likely to have entropion than the average dog. Bedford (2006) describes the condition’s incidence in Shar pei as “extremely high”.
5. Diagnosis
The diagnosis is made by examination of the eyes.
6. Genetics
A strong breed predisposition to entropion is known in Shar pei, connected to characteristics of their breed, but the exact genetic causes are currently not known.
7. How do you know if an animal is a carrier or likely to become affected?
Physical examination is the only way of determining the presence of entropion. Puppies should be examined carefully prior to purchase and should only be purchased if free of the condition (because a demand for unaffected animals will lead to a healthier population of dogs with less risk of suffering from this chronic and serious, painful condition).
It is also recommended not to purchase a puppy if a parent has or had the condition, though it may be difficult to assess if corrective surgery has taken place.
8. Methods and prospects for elimination of the problem
As entropion in the Shar pei is a consequence of their breed characteristics, it seems unlikely that it will be possible to eliminate the condition from the breed without changing conformation (and breed standard) significantly. It may be possible to select for lines that are less severely affected, but such selection of unaffected or only mildly affected animals for breeding is likely to decrease the size of the gene pool significantly. Unfortunately, as the Shar pei is one of the breeds most severely affected by this condition, it may be impossible to eliminate entropion, or to do so in a reasonable time, without out-crossing to breeds that have a low incidence of the condition.
In tackling such polygenic disorders, Bell (2010) recommended the use of breeding values which take into account all genetic and phenotypic information available for the individual and its close relatives (including siblings). Healthy individuals with healthy relatives are likely to be the best animals to use for breeding (Bell 2010). To develop a breeding strategy based on breeding values in a country will require the cooperation of the majority of Bloodhound breeders in that country. Progress towards breeding a population with normal eyelids may not be quick and opinions differ as to whether it is ethically acceptable to breed animals whose welfare is likely to be compromised.
For further details about this condition, please click on the following:
(these link to items down this page)
- Clinical and pathological effects
- Intensity of welfare impact
- Duration of welfare impact
- Number of animals affected
- Diagnosis
- Genetics
- How do you know if an animal is a carrier or likely to become affected?
- Methods and prospects for elimination of the problem
- Acknowledgements
- References
1. Clinical and pathological effects
The eyelid of a dog is composed of three layers of tissue: the outer layer is of skin with eyelashes (in dogs only the upper lids have eyelashes), hair and sebaceous glands. The middle layer is of muscle, meibomian glands and collagenous connective tissue, and the inner layer is the conjunctiva (Renwick 2007). Conjunctival tissue lines the inner surface of both eyelids and part of the outer surface of the eyeball itself. Dogs also have a third eyelid, or nictitating membrane, which comes from the inner corner of the eye and which is also covered by the conjunctiva.
Eyelids are vital for the health of the eye surface. They provide physical protection, help spread the tear film that keeps the surface of the eye moist and remove debris during blinking. They also carry the lacrimal ducts that drain away excess tears (Renwick 2007). To perform these functions effectively, the eyelids need to have smooth edges that are in constant contact with the surface of the eye at all times (Renwick 2007).
Entropion is a condition in which the eyelid or part of an eyelid (and with it the eyelashes) turns inward. Generally, the lower eyelids are more often affected but in the Shar pei upper eyelids are also often involved (Helper 1989). Entropion results in irritation of the globe of the eye through repeated contact with facial hairs and eyelashes. This leads to increased tear production, conjunctivitis (inflammation of the conjunctiva -the tissues lining the eyelids), keratitis (inflammation of the cornea -the clear front surface of the eye) and abrasion and ulceration of the cornea.
Increased tear production may lead to constant wetting of skin around the eyes which, in turn leads to irritation and secondary infection of the skin. A painful eye tends to be tightly held shut (blepharospasm). In itself this blepharospasm causes muscle pain and may cause the eyelid to rub still more on the eye (called spastic entropion). A painful eye suffers further from photophobia - the sensation that pain is worse when stronger light is falling upon it. When there is conjunctivitis, there may be a discharge from the eye and where there is secondary infection this may be pusy. Infection may also affect the cornea. In response to longer-term corneal damage, blood vessels grow into it as part of an attempted repair mechanism, and the cornea becomes opaque and white in colour due to scar tissue (Renwick 1996, van de Woerdt 2004). This, and the holding shut of the eyelids both cause blindness. Blindness due to corneal opacities may be permanent, even if the entropion is subsequently corrected using surgery (Moore 1993).
In most breeds entropion is caused by having loose eyelids; however in Shar pei it is a compound effect of breed characteristics, including small deep-set eyes with a narrow ocular opening (termed micropalpebral fissure) (Ramsey 2001); many Shar pei have excessive, heavy wrinkling due to a genetic mutation which increases the amount of hyaluronan in the skin, causing the skin, including that of the eyelids, to be thickened and heavy (http://www.sharpei-clubofgb.co.uk/page.php?page_ID=120). Both brow ptosis – the presence of excessive folds on the head above the eyes, and facial folds – excessive skin on the cheeks, can contribute to entropion (Barnett 1988, van de Woerdt 2004). Mild cases have lateral lower eyelid entropion, however, severe cases can involve much of both the lower and upper lids (Renwick 2007). Bedford (2006) suggests extensive entropion is frequent in Shar pei. All of these complications can mean that entropion in Shar pei is more difficult to surgically correct than in other dogs, more extensive and multiple surgeries may be needed, with consequentially a greater impact on the dog’s well being.
Treatment of these defects involves surgery under anaesthesia, and attempts to create normal eyelid anatomy. Techniques are also used to remove excessive skin from eyelids and folds around the eyes and, in severely affected individuals, major facelift surgeries may be necessary (van der Woerdt 2004, Renwick 2007). Renwick (2007) recommends specialist assessment of each individual as further problems can be created by inappropriate treatment.
Shar pei frequently show entropion from the time their eyes open when a puppy (Renwick 2007). Affected puppies may need temporary procedures to alleviate pain and discomfort until assessment of the adult eyes can be made (Bedford 2006, Renwick 2007).
2. Intensity of welfare impact
The welfare impact of entropion can vary from mild to severe depending on the severity of the facial and eyelid abnormalities present. Many Shar pei are severely affected and are likely to suffer from constant irritation, discomfort and pain which may be severe, especially at times when eye tissues are infected. If the disease processes progresses, vision can become permanently impaired; with blindness due to keeping the affected eye shut or due to scarring of the surface of the eye seen.
Treatments may have adverse welfare implications in themselves, through the stress associated with travel for veterinary therapy, applications of eye medication and surgery of the face and eyelids.
3. Duration of welfare impact
The condition, and the distress and pain it causes, are potentially life long, often starting soon after the affected pups eyes open at two weeks of age (Bedford 1988, Yaphé 2005) unless treated. During their life, individuals may suffer episodes of greater severity associated with periods of infection.
Treatment is not always successful and, in itself, can have significant welfare implications as it is based on surgery, and sometimes repeated surgeries but also may involve regular eye medication
4. Number of animals affected
The number of Shar pei affected with entropion is unknown, however, in a USA epidemiological study Shar pei were shown to be 131 times more likely to suffer from entropion than an average dog (Lund 2007). This study also showed Shar pei to be 9.5 times at greater risk of ectropion (eyelids rotating outwards) and 5.5 times more likely to develop prolapsed third eyelid glands (Lund 2007).
This high frequency of entropion in the breed is emphasised by many authors (eg Helper 1989, Bedford 2006, Renwick 2007; Williams 2008).
5. Diagnosis
Careful examination of the eye will lead a veterinary surgeon to make the diagnosis. Distinguishing to what extent entropion is due to structural abnormalities (a narrow ocular opening or loose eyelids and wrinkled skin) and how much is due to muscular contraction of a painful eye can be more difficult and involves applying local anaesthetic to the eye. Spastic entropion should resolve with local anaesthetic application – this is a diagnostic test rather than a treatment. More specialist examinations, requiring staining of the tears and specialist equipment, will help to determine the extent of damage that has occurred to the eye itself. With moderate-severe disease, the amount of pain in the eye can make it impossible to examine the eye properly without anaesthetising the dog
6. Genetics
Shar pei are highly predisposed to entropion ie they are more likely to have this condition than other dogs. Entropion does not have a simple genetic cause and the exact genetic factors have not been established, however, in Shar pei its occurrence is intimately connected to their breed characteristics and conformation.
7. How do you know if an animal is a carrier or likely to become affected?
A prospective owner should look for any inclination of the puppy to not hold its eyes completely open or to be blinking. There should be no discharges from the eyes. Although some puppies may grow out of mild entropion, whether this will happen in a particular individual cannot be predicted. A veterinary examination can be sought. Buying affected animals is likely to result in this welfare problem being perpetuated. It has been suggested that if signs appear after purchase the puppy should be returned to its breeder.
The parents of any puppy should be free from entropion themselves and should not have had corrective surgery for the condition. It may be difficult to find a puppy that is free of the condition because of its high frequency of incidence within the breed. Currently it may also be difficult to identify individuals which have had corrective surgery.
8. Methods and prospects for elimination of the problem
Clear identification and neutering of all dogs which have had surgical interventions seems vital. However, it is the Shar pei breed characteristics of small eyes, with loose wrinkled thickened skin that brings with it the primary anatomical abnormalities that cause entropion and other skin conditions (see skin fold dermatitis). It seems unlikely therefore that it will be possible to eliminate the condition from the breed without changing conformation (and breed standard) significantly. It may be possible to select for lines that are less severely affected, but such selection of unaffected or only mildly affected animals for breeding is likely to decrease the size of the gene pool significantly.
Recently there has been debate in the UK, about the morality of breeding animals with exaggerated anatomical features that can cause suffering. The UK Kennel club has changed its breed description for the Shar pei (available at http://www.thekennelclub.org.uk/item/173). The UK Kennel Club also instigated a ‘breed watch’ for excessive amounts of wrinkling and conformational abnormalities of the eyelids within the Shar pei breed (UK Kennel Club 2011). Some other Kennel clubs worldwide have also done this eg Australian Kennel club, whilst others have not, so breed standards worldwide do vary.
The Shar pei is one of the breeds most severely affected with entropion, having an “extremely high” incidence of the condition (Bedford 2006). It may be impossible to eliminate this problem, or to do so in a reasonable time, without out-crossing to breeds that are not affected by these predisposing characteristics.
In tackling such polygenic disorders, Bell (2010) recommended the use of breeding values which take into account all genetic and phenotypic information available for the individual and its close relatives (including siblings). Healthy individuals with healthy relatives are likely to be the best animals to use for breeding (Bell 2010). To develop a breeding strategy based on breeding values in a country will require the cooperation of the majority of Bloodhound breeders in that country. Progress towards breeding a population with normal eyelids may not be quick and opinions differ as to whether it is ethically acceptable to breed animals whose welfare is likely to be compromised.
9. Acknowledgements
UFAW is grateful to Rosie Godfrey BVetMed MRCVS and David Godfrey BVetMed FRCVS for their work in compiling this section.
10. References
Barnett KC (1988) Inherited eye disease in the dog and cat. Journal of Small Animal Practice 29: 462-475
Bedford P (2006) Hereditary Diseases of the Canine Eyelid and Cornea. World Small Animal Veterinary Association World Congress Proceedings, Prague, Czech Republic, October 2006
Helper LC (1989) Diseases and surgery of the lids and lacrimal apparatus. In: Magrane’s Canine Ophthalmology 4th ed. pp 51.Lea & Febiger: Philadelphia, USA
Lund E (2007) Eyelid disease: All dogs are not equal. Data Savant: 16-20
Moore CP (1993) Diseases of the eyelid, conjunctiva, and third eyelid. In:Bojrab MJ (ed) Disease Mechanisms in Small Animal Surgery 2nd edn. pp139. Lea & Febger: Philadelphia USA
Ramsey DT (2001) Conditions of the Eyelids and Ocular Adnexa in Dogs and Cats. The25th Annual Waltham/OSU Symposium Small Animal Ophthalmology October 27—28, 2001
Renwick P (1996) Diagnosis and treatment of corneal disorders in dogs. In Practice: 315-18
Renwick P (2007) Eyelid surgery in dogs In Practice 29: 256-271
The Kennel Club (UK) (2011) Breed Watch information for the Shar pei. Available from: http://www.the-kennel-club.org.uk/services/public/breeds/watch/display.aspx?breed=Shar+Pei. Accessed 6.4.11
van der Woerdt A (2004) Adnexal surgery in dogs and cats. Veterinary Ophthalmology 7: 284–290
Williams D (2008) Abnormal Adnexa--Entropion, Ectropion, etc! World Veterinary Congress, Vancouver, British Columbia, Canada • July 27–31, 2008. WVA
Yaphé W (2005) Lecture 2 - Eyelid and Third Eyelid Disease On-line VIN Associate. http://www.vin.com/Members/CMS/Misc/default.aspx?id=6799. Accessed 28.3.11
http://www.sharpei-clubofgb.co.uk/page.php?page_ID=120
http://www.thekennelclub.org.uk/item/173
© UFAW 2011
Credit for main photo above:
http://depositphotos.com/2455939/stock-photo-puppy-shar-pei.html ©Depositphotos.com/cynoclub
