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Genetic Welfare Problems of Companion Animals
An information resource for prospective pet owners
Cavalier King Charles Spaniel (CKCS)
Congenital Keratoconjunctivitis Sicca and Ichthyosiform Dermatosis
Related terms: ichthyosis, curly coat, dry eye, “dry eye and curly coat”, “dry eye and rough coat,” fish scale disease
Outline: In keratoconjunctivitis sicca there is a failure of tear production. As a result, there is painful damage to the surface of the eyes is damaged and they are prone to infection. This disease is often accompanied by ichthyosiform dermatitis which is caused by abnormal rates of cell turnover in the skin. Both are present from birth in affected puppies. A genetic test is available which enables detection of animals that carry the recessive gene (and which should not be used for breeding).
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Summary of Information
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1. Brief description
This syndrome is unique to the Cavalier King Charles spaniel (CKCS). It has only recently been reported and described scientifically but has apparently been known to breeders in the UK and elsewhere for some time (Barnett 2006).
There are two components to the disease: (i) keratoconjunctivitis sicca – failure of tear production leading to severe eye damage due to the drying of the surface of the eye leading to trauma and infection; and (ii) ichythosiform dermatosis – failure of the surface of the skin to function normally leading to scaliness, itchiness and pain. Both are present from birth in affected puppies and are difficult to treat, so most affected animals are euthanased.
2. Intensity of welfare impact
Both the eye and skin disease cause severe welfare problems that respond poorly to treatment. Keratoconjunctivitis sicca (KCS) is a painful condition, especially when there are any secondary infections or corneal ulcers. The form of this disease seen in Cavalier King Charles Spaniels tends to be more severe than that which occurs in other dog breeds (Sanchez et al 2007). KCS can lead to blindness, which can also have adverse welfare consequences.
The skin disease, ichthyosiform dermatosis, causes mild to severe distress, with generalised itchiness of the body progressing to soreness, particularly of the feet so that affected animals experience pain when standing or walking.
3. Duration of welfare impact
The disease problems associated with these conditions are evident at birth in affected animals and progress throughout life, which is often short because affected puppies tend to be euthanased on welfare grounds (Barnett 2006, Animal Health Trust 2011).
4. Number of animals affected
Keratoconjunctivitis sicca and ichthyosiform dermatosis (KCSID) has only been scientifically recorded and described recently (Barnett 2006). However in his paper on the disease, Barnett (2006) indicated that it had been quite widely known among breeders for some time and also that, in retrospect, it seemed possible that some cases of eye disease reported in the scientific literature may have been cases of KCSID (Alhaidari et al 1994). We are unaware of any data on the proportion of Cavalier King Charles Spaniels that are affected.
5. Diagnosis
The disease is evident to experienced breeders of CKCS in affected puppies from birth, because of the appearance of the coat. The typical changes in the eyes due to the disease are usually apparent soon after they open, at around two weeks old. The Schirmer tear test is usually used to confirm a diagnosis of KCS. A genetic test available at the Animal Health Test can also be used to identify affected puppies (Animal Health Trust 2011).
6. Genetics
A definitive genetic test for this disease was developed soon after the condition was discovered (Hartley et al 2009) and is now available for widespread use (Anonymous 2011, Animal Health Trust 2011). It followed the discovery of the recessive gene that is responsible for the condition. Animals with two copies of this recessive gene are affected with the disease but those with only one copy do not develop the disease themselves but are carriers. Approximately half of such dog’s offspring are likely to be affected with the disease, if they are bred with another dog that is also a carrier.
7. How do you know if an animal is a carrier or likely to become affected?
It is possible to detect a clinically affected animal by examination of the hair coat from birth. The signs of eye disease will also be evident from early life, but testing for keratoconjunctivitis sicca using a Schirmer tear test (which measures rate of tear production), may be difficult in young puppies (Barnett 2006).
Carriers can not be detected clinically but a genetic test is now available that makes their detection possible at any age (Animal Health Trust 2011).
8. Methods and prospects for elimination of the problem
Cavalier King Charles spaniels should be tested for the abnormal gene prior to breeding and two carriers should not be bred together. Ideally, carriers should not be used for breeding at all but because this breed is affected by several serious genetic disorders, any breeding strategy has to take these into account also, and in trying to tackle all these disorders simultaneously, there may be circumstances in which it is acceptable to breed a carrier with an individual known to be free of the genetic defect (Bell 2010, Animal Health Trust 2011).
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 of likely to become affected?
- Methods and prospects for elimination of the problem
- Acknowledgements
- References
1. Clinical and pathological effects
This syndrome is unique to the Cavalier King Charles spaniel (CKCS). It has only recently been reported and described scientifically but has apparently been known to breeders in the UK and elsewhere for considerably longer (Barnett 2006).
There are two components to the disease as outlined below and both are present from birth.
- Keratoconjunctivitis sicca – failure of tear production leading to severe eye damage as a result of drying of the surface of the eye and predisposing to infection (see below).
- Ichythyosiform dermatosis – failure of the surface of the skin to function normally leading to scaliness, itchiness and pain (see below).
Both aspects of this condition adversely affect welfare. They are difficult to treat and affected puppies tend to be euthanased on welfare grounds, although less severely affected animals may respond to treatment.
Keratoconjunctivitis sicca
Keratoconjunctivitis sicca (KCS) is the result of a deficiency in the aqueous part of the tear film (Crispin 2002, Herring 2004), but it may be exacerbated by abnormalities of mucin, one of the components of tears (Crispin 2002). For a healthy eye, the surface and surrounding tissues need to be constantly bathed in tears; without this, the eye becomes dry, inflamed and diseased, which results in the signs of KCS.
The tear film produced by healthy eyes covers the whole front surface of the eye: the cornea (the clear front of the eye), parts of the sclera (the whites of the eye), both sides of the third eyelid and the conjunctiva (the tissue which lines the eyelids and covers the eyeball to where the sclera becomes apparent). This film of fluid consists of three layers – an outer oily layer, a middle aqueous layer and an inner mucin layer (Renwick 1996, Crispin 2002). In KCS it is a deficiency in the aqueous layer which leads to the eye disease (Renwick 1996, Crispin 2002).
The aqueous component of tears is produced by the lacrimal gland, which is sited in tissue adjacent to the upper and outer part of the eyeball, by accessory lacrimal glands and the nictitans gland under the third eyelid (Crispin 2002). The cornea, which in a healthy eye is clear and transparent, is an unusual tissue in that it is avascular – that is, it doesn’t have a blood supply. It depends on tears to supply it with the oxygen and nutrients it needs and to provide it with components of the immune system to protect it and keep it healthy (Crispin 2002).
There is no cure for KCS. Medical approaches to its alleviation involve the application of drugs to the eyes for the following reasons.
- To suppress immune-mediated inflammation that leads to destruction of the lacrimal and nictitans glands. Drugs used for this include cyclosporine A and tacrolimus (Herring 2004, Berdoulay et al 2005).
- To provide artificial tears.
- To provide antibiotics to control the secondary bacterial infections which commonly occur in affected animals.
- Occasionally, the administration of corticosteroid drops can also be beneficial but these can only be safely used if no corneal ulcers are present (Herring 2004).
Since there is no cure for keratoconjunctivitis sicca, treatments have to be maintained throughout the life of the animal. Affected CKCS puppies often do not respond well.
Some Cavalier King Charles spaniels also develop a later-onset form of KCS. This form, which typically affects middle-aged dogs (Sansom & Barnett 1985, Padgett 1998), is seen in other breeds also and occurs as a result of an autoimmune reaction against the lacrimal glands. Dogs with this form of the disease are more likely to respond to medical treatment than those with early-onset KCS. That the results of a survey of KCS in CKCSs showed that there were two peaks in the age distribution of keratoconjunctivitis sicca, one at birth and one in middle age, supports the view that there are two distinct underlying causes to KCS in this breed (Sanchez et al 2007).
Ichthyosiform dermatosis
Many Cavalier King Charles spaniels affected with KCS are also commonly affected by ichthyosiform dermatosis too. Ichthyosiform dermatosis is a skin disease which has similarities in appearance to ichthyosis, the 'umbrella' term for a group of conditions seen in humans and occasionally reported in dogs. Individuals affected with these conditions have skin that is very scaly and which can resemble fish skin (Scott et al 2001. Ichthyosis derives from the Greek word for fish ‘ichthys’).
The skin has three main layers: the epidermis (outer layer), dermis (middle) and subdermis (inner layer). Ichthyosis is a disease of the epidermis. The epidermis itself consists of several layers: the basal layer, spinous layer, granular layer and the outer cornified layer. The cornified layer is composed of dead skin cells, full of the protein keratin, and covered by a matrix of lipids (fats).
In ichthyosis, the rate of production and turnover of epidermal cells is greatly accelerated which causes pieces of the cornified (outer) layer to be frequently shed in large pieces. This is a keratinisation defect – a defect in the production and maintenance of the outer, cornified, skin layer (Kwochka 1993).
The resulting scaliness may itself cause skin irritation but, in addition, the abnormal skin is particularly susceptible to bacterial or fungal infections (Kwochka 1993) which may cause itchiness or discomfort.
Ichthyosiform dermatosis in CKCS seems to particularly affect the feet of some individuals causing ulceration of skin, shedding of claws, pain and lameness (Barnett 2006).
2. Intensity of welfare impact
The effects of this disease on both eyes and skin can have severe welfare effects: resulting in prolonged discomfort, itching and severe pain. Keratoconjunctivitis sicca is especially painful when secondary infections occur or when there is corneal ulceration. The form of the disease seen in Cavalier King Charles spaniels tends to be more severe than that in other breeds (Sanchez et al 2007) and responds poorly to treatment. It can lead to blindness, which can also have adverse welfare consequences: not being able to see may directly affect quality of life and may increase the risk of painful injuries.
The skin disease, ichythosiform dermatosis, causes mild to severe distress, with generalised itchiness of the body progressing to soreness, particularly of the feet so that affected animals experience pain when standing or walking.
3. Duration of welfare impact
The disease problems associated with these conditions are evident at birth in affected individuals and progress throughout life, which is often short because affected puppies tend to be euthanased on welfare grounds (Barnett 2006, Animal Health Trust 2011). The duration of the welfare effects may, in many cases, therefore be limited to a few weeks but can be much longer in dogs that are not euthansed.
4. Number of animals affected
Keratoconjunctivitis sicca and ichthyosiform dermatosis has only been scientifically recorded and described recently (Barnett 2006). However in his paper on the disease, Barnett (2006) indicated that it had been quite widely known among breeders for some time and also that, in retrospect, it seemed possible that some cases of eye disease reported in the scientific literature may have been cases of KCSID (Alhaidari et al 1994). We are unaware of any data on the proportion of Cavalier King Charles Spaniels that are affected with the disease.
Cavalier King Charles spaniels have been found to be 11 times more likely to be affected by keratoconjunctivitis sicca than average for dogs of all breeds (Kaswan & Salisbury 1990). However, this statistic includes dogs with the adult-onset type of the disease which is thought not to be related to the more severe KCSID.
5. Diagnosis
The disease is evident to experienced breeders of CKCS in affected puppies from birth, because of the appearance of the coat. The typical changes in the eyes due to the disease are usually apparent soon after they open, at around two weeks old. The Schirmer tear test (which measures the rate of tear production) is usually used to confirm a diagnosis of KCS. However, this test is unreliable in young puppies as there is a large over-lap of results between affected and non-affected individuals (Barnett 2006). A definitive genetic test is available at the Animal Health Test that can be used to identify affected and carrier animals at any age (Animal Health Trust 2011).
6. Genetics
A definitive genetic test for this disease was developed soon after the condition was discovered (Hartley et al 2009) and is now available for widespread use (Anonymous 2011, Animal Health Trust 2011). It followed the discovery of the recessive gene that is responsible for the condition. Animals with two copies of this recessive gene are affected with the disease but those with only one copy do not develop the disease themselves but are carriers. Approximately half of such dog’s offspring are likely to be affected with the disease, if they are bred with another dog that is also a carrier.
7. How do you know if an animal is a carrier or likely to become affected?
It is possible to detect a clinically affected animal by examination of the hair coat from birth. The signs of eye disease will also be evident from early life but testing for keratoconjunctivitis sicca using a Schirmer tear test (which measures rate of tear production), may be difficult in young puppies (Barnett 2006).
Carriers cannot be detected clinically but a genetic test is now available that makes their detection possible at any age (Animal Health Trust 2011).
8. Methods and prospects for elimination of the problem
Affected animals should not be used for breeding. This is easily achieved as the disease is apparent before breeding age (and, in many cases, affected animals do not reach breeding age).
Cavalier King Charles spaniels should be tested for the abnormal gene prior to breeding and two carriers should not be bred together. Ideally, carriers should not be used for breeding at all but because this breed is affected by several serious genetic disorders, any breeding strategy has to take these into account also, and in trying to tackle all these disorders simultaneously, there may be circumstances in which it is acceptable to breed a carrier with an individual known to be free of the genetic defect (Bell 2010, Animal Health Trust 2011).
Breeding plans for Cavalier King Charles spaniels should be based on 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). The development of a good national breeding strategy depends on the cooperation of the majority of breeders to ensure that all dogs are tested so that breeding values can be calculated.
Outbreeding with genetically healthy individuals of other breeds may enable the more rapid elimination of this disease.
9. Acknowledgements
UFAW is grateful to Rosie Godfrey BVetMed MRCVS and David Godfrey BVetMed FRCVS for their work in compiling this section and to Dr James Yeates for his contribution.
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10. References
Alhaidari Z, Ortonne J-P and Pisani A (1994) Congenital ichthyosis in two cavalier King Charles spaniel littermates. Veterinary Dermatology 5: 117–121
Animal Health Trust (2011) Dry eye curly coat syndrome in the cavalier King Charles spaniel. http://www.aht.org.uk/genetics_curleycoat.html accessed 19.9.2011
Anonymous (2011) New DNA tests for Cavalier King Charles spaniels. Veterinary Record 168: 370
Barnett KC (2006) Congenital keratoconjunctivitis sicca and ichthyosiform dermatosis in cavalier King Charles spaniels. Journal of Small Animal Practice 47: 524-528
Bell JS (2010) Genetic Testin0g and Genetic Counseling in Pet and Breeding Dogs World Small Animal Veterinary Association World Congress Proceedings, Geneva, Switzerland June 2-5th 2010 http://www.vin.com/Members/Proceedings/Proceedings.plx?CID=wsava2010&PID=pr56159&O=VIN accessed 19.9.2011
Berdoulay A, English RV and Nadelstein B (2005) Effect of topical 0.02% tacrolimus aqueous suspension on tear production in dogs with keratoconjunctivitis sicca. Veterinary Ophthalmology 8: 225-32
Crispin S (2002) The lacrimal system in Petersen-Jones S and Crispin S eds. BSAVA Manual of Small Animal Ophthalmology 2nd Ed. British Small Animal Veterinary Association, Cheltenham, Gloucestershire, UK. 105-123
Hartley C, Barnett KC, Mellersh CS, Pettitt L and Forman OP (2009) Congenital keratoconjunctivitis sicca and ichthyosiform dermatosis (ckcsid) in the Cavalier King Charles Spaniel(CKCS)dog: a candidate gene study. Veterinary Ophthalmology 12: 379–385
Herring I (2004) Keratoconjunctivitis sicca. VIN associate. http://www.vin.com/Members/Associate/Associate.plx?DiseaseId=506. Accessed 19.9.2011
Kaswan RL and Salisbury MA (1990) A new perspective on canine keratoconjunctivitis sicca. Veterinary Clinics of North American: Small Animal Practice 20: 595
Kwochka KW (1993) Overview of normal keratinisation and cutaneous scaling disorders of dogs. In Griffin GE, Kwochka KW & McDonald JM’s (eds) Current Veterinary Dermatology , Mosby Year Book, St Louis pp167-175
Padgett GA (1998) Control of canine genetic diseases. Howell Book House, New York, New York 198
Renwick P (1996) Diagnosis and treatment of corneal diseases in dogs. In Practice 18: 315-328
Sanchez RF, Innocent G, Mould J and Billson FM (2007) Canine keratoconjunctivitis sicca: disease trends in a review of 229 cases. Journal of Small Animal Practice 48: 211-217
Sansom J and Barnett KC (1985) Keratoconjunctivitis sicca in the dog: a review of 200 cases. Journal of Small Animal Practice 26: 121-131
Scott DW, Muller GH and Grifffin CER (2001) Congenital and hereditary defects. In: Muller and Kirk’s Small Animal Dermatology 6th edition. WB Saunders, Philadelphia pp913-1003
© UFAW 2011
Credit for main photo above:
By Philippe Brizard (Own work) [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
