Genetic Welfare Problems of Companion Animals

Bloodhound

Ectropion, macroblepharon and entropion

Outline: Bloodhounds have been selected for excessive drooping facial skin, and because of this are prone to eyelid abnormalities. The lower lids may be everted (turned-out). This condition is known as ectropion. Conversely, the upper lids may be inverted (turned-in); a condition called entropion.  Ectropion disrupts the function of the lower lid in protecting the eye and drainage of tears and entropion causes chronic abrasion of the surface of the eye.  Both conditions predispose 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

Despite the associated health problems, Bloodhounds have been bred to have conformational abnormalities which affect the eyes, including overlong eyelids and eyelid laxity, in order to produce the breeders’ desired ‘hang dog’ appearance (Stockman 1983; Bedford 1988; Herring 2007). The severity of the associated clinical conditions is linked to the degree of the hereditary exaggerations in the individual (Bedford 1988; Herring 2007).

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 drainage system for tears (the lacrimal ducts) (Renwick 2007). In order to perform these jobs successfully they need to have a smooth edge that stays in constant contact with the surface of the eyeball at all times (Renwick 2007). This is often not the case in Bloodhounds because of two physical abnormalities of the eyelids – inward turning of the upper eyelid (entropion) and outward turning of the lower eyelid (ectropion).

Dogs with ectropion are prone to conjunctivitis (inflammation of the conjunctiva), with or without secondary bacterial infection, and, if the corneal exposure is prolonged, then keratitis (inflammation of the cornea) or keratoconjunctivitis sicca (dry eye) will occur (Bedford 1988; http://www.upei.ca/cidd/Diseases/ocular%20disorders/ectropion.htm; Renwick 2007). Tear wetting of the face may also occur because of the associated displacement of the lacrimal duct and obstruction of the tear drainage system seen in animals with ectropion.

Entropion results in irritation of the surface 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. 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.

Bloodhounds suffering from ectropion and/or entropion may require surgery to correct these anatomical defects.

2. Intensity of welfare impact

This can vary from mild to severe depending on the severity of the facial and eyelid abnormalities present. Ectropion alone may cause some discomfort especially if inflammation and infection of the conjunctiva are present. Where there is combined ectropion and entropion, affected dogs are likely to suffer from constant irritation and pain which may be severe, especially at times when eye tissues are infected. If the disease processes progress, vision can become permanently impaired.

3. Duration of welfare impact

The conditions are life-long, often starting soon after the affected pups eyes open at two weeks of age (Bedford 1988, Yaphé 2005), but during their life individuals may sufferepisodes of greater severity associated with periods of infection.

4. Number of animals affected

Ectropion and entropion are frequently seen in Bloodhounds (Bedford 1988, Gelatt and Gelatt 2001; http://www.upei.ca/cidd/Diseases/ocular%20disorders/ectropion.htm; Herring 2007). However, as far as we are aware, there are no data on the prevalence of these conditions.

5. Diagnosis

Diagnosis is confirmed by examination of the eyes and face.

6. Genetics

The eyelid abnormalities are thought to be due to mulitiple genes (ie to be polygenic). The eyelid abnormalities are linked to the exaggerated facial features of this breed (Rubin 1989).

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

Entropion and ectropion are common in Bloodhounds. We are unaware of any data relating to whether animals may be genetic carriers of this condition without themselves being affected.Prior to purchase of a puppy, the puppy and its parents and siblings should be examined carefully and individuals chosen on the basis of absence of signs of these conditions.

8. Methods and prospects for elimination of the problem

As far as we are aware there are no breeding schemes aimed at tackling these eyelid problems in Bloodhounds. The breed standards for Bloodhounds vary from country to country around the world and some encourage the exaggerated facial features that lead to these conditions.

It seems very likely that avoiding breeding from any animals that have had ectropion or entropion would be effective in reducing the prevalence of these welfare problems (Stockman 1983, Herring 2007). Because of the high prevalence of these diseases, selection only of unaffected or only mildly affected animals for breeding might be likely to decrease the size of the gene pool significantly, unless animals are outcrossed with dogs of unaffected breeds.

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

Despite the associated health problems, Bloodhounds have been selected and bred for conformational abnormalities that result in over-long eyelids and eyelid laxity in order to produce their desired ‘hang dog’ appearance (Stockman 1983, Bedford 1988, Herring 2007). The severity of the associated clinical conditions is linked to the extent of the hereditary exaggerations (Bedford 1988, Herring 2007).

The eyelids are 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 filmthat 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). Bloodhounds are prone to inward rotation (entropion) of the edge of the upper eyelid and outward rotation (ectropion) of the edge of the lower eyelid.  They also tend to have excessive facial skin, both above and below the eyes. This tends to sag under gravity and is called facial droop. Through artificial selection, these traits have been purposefully exaggerated in Bloodhounds to produce a breed with a doleful appearance, due to drooping face and ears. This has altered the eyelid anatomy leading to the disease conditions described here (Bedford 1988, Herring 2007)

1.  Ectropion

Many Bloodhounds have abnormally large eyelids (macroblepharon) which results in an unusually large space between the eyelids.  Because of their excessive facial skin and resulting facial droop, there is commonly poor support of the outer corner of the eyelids (the lateral canthus) (Bedford 1988). These abnormalities encourage ectropion – the outward rotation, eversion, of the lower eyelids leading to increased exposure of the conjunctiva, nictitating membrane and cornea (the clear surface at the front of the eye) (Bedford 1988). The eyes are therefore prone to conjunctivitis (inflammation of the conjunctiva) and to bacterial infections and, if the corneal exposure is prolonged, to keratitis (inflammation of the cornea) or keratoconjunctivitis sicca (dry eye) (Bedford 1988; http://www.upei.ca/cidd/Diseases/ocular%20disorders/ectropion.htm; Renwick 2007). Tear wetting and staining of the face may also occur because of the associated displacement of the lacrimal duct, which should normally be at the edge of the eyelid and in contact with the surface of the eye, and obstruction of the tear drainage system seen in animals with ectropion. The constant dampening of skin also leads to skin irritation and infection.

2.  Entropion and facial droop

Macroblepharon is often severe enough to cause “diamond eye” in Bloodhounds. This is when there is both ectropion and entropion simultaneously (Renwick 2007). It is often accompanied by facial droop with excessive, redundant skin folds on the head and laxity (looseness) of the lateral canthus (corner of the eye) which increases the severity of upper eyelid entropion (Renwick 2007).

Entropion, the inward rotation of the edge of the eyelid, results in irritation of the surface of the eye through abrasion by repeated contact with the hairs and eyelashes that, but for the rotation of the edge of the eyelid, would be on its outer surface. 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).

Ectropion alone is less serious and may not require surgical correction, although the associated conjunctivitis needs to be treated as it arises. However, when there is entropion also, the effects on the eyes are more serious. Surgical correction is often necessary if diamond eye, facial droop or ptosis (upper eyelid droop) are causing complications (Herring 2007, Renwick 2007). Surgical treatments of ectropion, entropion, “diamond eye” and facial droop are complex and have to be based on specialist assessment of each individual, as further problems can be created by inappropriate treatment (Renwick 2007). Various eyelid surgeries and, in severely affected individuals, major facelift surgeries may be necessary (van der Woerdt 2004, Renwick 2007).

Return to top

2. Intensity of welfare impact

The welfare impacts depend on the severity of the eyelid abnormalities present and the disease conditions that arise because of these. The effects of ectropion alone may be relatively mild, causing some discomfort but, when inflammation and infection of the conjunctiva are present, affected individuals will experience greater discomfort and pain. If keratitis is present then the discomfort is likely to be greater still.

The welfare effects of entropion likewise can range from mild to severe. The disease conditions associated with entropion can cause constant irritation and pain, which may be severe.

In longstanding cases vision can be significantly and permanently impaired and this may also affect the dog’s quality of life.

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.

Return to top

3. Duration of welfare impact

Entropion can appear soon after puppies’ eyes have opened or upon reaching maturity (Yaphé 2005). Ectropion usually appears soon after a puppy’s eyes open at two weeks of age (Bedford 1988).

The disease conditions that can occur due to entropion are chronic and may cause some irritation, discomfort and pain throughout life or may suffer episodes of greater severity associated with periods of infection.

Ectropion by itself is less severe but may cause recurrent bouts of conjunctivitis lasting from a few days to a few weeks through life.

Surgical treatment is not always successful.

Return to top

4. Number of animals affected

Macroblepharon and facial droop are often considered to be a breed characteristic of the Bloodhound so these dogs frequently show ectropion and entropion (Bedford 1988, Gelatt and Gelatt 2001; http://www.upei.ca/cidd/Diseases/ocular%20disorders/ectropion.htm; Herring 2007). However, we are not aware of data on the proportion of animals with these conditions.

Return to top

5. Diagnosis

Diagnosis is made by examination of the face and eyes using specific ophthalmological equipment and tests.

Return to top

6. Genetics

The eyelid abnormalities are thought to be due to mulitiple genes (ie to be polygenic). The eyelid abnormalities are linked to the exaggerated facial features of this breed (Rubin 1989). The genes involved have not been identified.

Return to top

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

Entropion and ectropion are common in Bloodhounds. We are unaware of any data relating to whether animals may be carriers of this condition without themselves being affected.Prior to purchase of a puppy, the puppy and its parents and siblings should be examined carefully and animals chosen on the basis of absence of signs of these conditions.

Prospective owners should look for any inclination of the puppy to not hold its eyes completely open, for excessive blinking and for any gap between the lower eyelid and the surface of the eye. There should be no discharges from the eyes.  Buying affected animals is likely to increase the likelihood of this welfare problem being perpetuated.

Return to top

8. Methods and prospects for elimination of the problem

The UK breed standard (updated in 2009) specifies that the eyelids should be “oval in shape, meeting the cornea perfectly without any irregularity in their contour. Eyes should be free from any interference from the eyelashes. Any obvious signs of eye irritation must be heavily penalised. The eyesight of the hound should be unimpeded” (http://www.thekennelclub.org.uk/item/16). In the UK there is also a Kennel Club “breed health watch” for the Bloodhound, highlighting the need to avoid ectropion, entropion and the excessive facial skin folds and droop that add to these conditions (http://www.the-kennel-club.org.uk/services/public/breeds/watch/display.aspx?breed=Bloodhound).

In the USA this is not the case and the AKC (American Kennel Club) Bloodhound breed standard includes “eyes deeply sunk in the orbits, the lids assuming a lozenge or diamond shape, in consequence of the lower lids being dragged down and everted by the heavy flews” (http://www.akc.org/breeds/Bloodhound/). The AKC breed standard also requires “superabundant” loose skin on the head.

Whether the recent tightening of the breed standard in the UK (as above) is reducing the prevalence of these eyelid diseases is not yet known, but  it seems very likely that avoiding breeding from any animals that have had ectropion or entropion would be likely to be helpful (Stockman 1983, Herring 2007). It is important also not to breed from animals with eyelid abnormalities that have been corrected surgically.

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.

Return to top

9. Acknowledgements

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

Return to top

10. References

Bedford PGC (1988) Conditions of the eyelids in the dog Journal of Small Animal Practice 29: 41-28

Bell JS (2010) Genetic Testing and Genetic Counseling in Pet and Breeding Dogs. World Small Animal Veterinary Association World Congress Proceedings

Gelatt K and Gelatt J (2001) Small Animal Ophthalmic surgery. Practical techniques for the veterinarian. Butterworth Heinemann: Edinburgh

Herring I (2007) Ectropion. On-line. VIN Associate. http://www.vin.com/Members/Associate/Associate.plx?DiseaseId=1208. Accessed 28.3.11

Moore CP (1993) Diseases of the eyelid, conjunctiva, and third eyelid. In Bojrab ME (ed) Disease Mechanisms in Small Animal Surgery 2nd edn. pp139 Lea and Febger: Philadelphia, USA

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

Rubin LF (1989) Inherited Eye Diseases in Purebred Dogs. Williams and Williams; Baltimore, USA

Stockman M (1983) Inheritable defects in dogs: 3. In Practice: 202-206

van der Woerdt A (2004) Adnexal surgery in dogs and cats. Veterinary Ophthalmology 7: 284–290

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.akc.org/breeds/bloodhound/. Accessed 28.3.11

http://www.thekennelclub.org.uk/item/16. Accessed 28.3.11

http://www.the-kennel-club.org.uk/services/public/breeds/watch/display.aspx?breed=Bloodhound. Accessed 28.3.11

http://www.upei.ca/cidd/Diseases/ocular%20disorders/ectropion.htm. Accessed 28.3.11

© UFAW 2012

Credit for main photo above:

By Claudia Krebs, modyfikacja Pleple2000 [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], via Wikimedia Commons