Genetic Welfare Problems of Companion Animals

An information resource for prospective pet owners

Cavalier King Charles Spaniel

Cavalier King Charles Spaniel (CKCS)

Primary Secretory Otitis Media

Related terms: otitis media, PSOM, glue ear, middle ear effusion, secretory otitis media, SOM

Outline: In primary secretory otitis media, mucoid fluid accumulates within the inner ear. This may be because of poor drainage associated with consequences of the brachycephalic head shape. The condition is reported to be common in Cavalier King Charles spaniels. It causes pain through pressure on the eardrum.


Summary of Information

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1. Brief description

Cavalier King Charles spaniels (CKCSs) are commonly affected by primary secretory otitis media (PSOM), a condition in which mucus accumulates within the middle ear (Cole 2007). This seems to be associated with the abnormally thick soft palate seen in many dogs of this breed (Hayes et al 2010). The mucoid fluid within the middle ear may cause pain (Stern-Sertholtz et al 2003; Cole 2007) but many affected dogs do not show obvious signs (Hayes et al 2010). Clinical signs include pain in the head and neck (which may result in a head tilt or in the head being held in a horizontal position); ataxia (unsteadiness when walking), facial nerve damage, nystagmus (uncontrolled twitching of the eyes), seizures, itching around the ears, inflammation of the external ear canal (otitis externa), fatigue and varying degrees of deafness (Stern-Sertholtz et al 2003). Similar signs occur in syringomyelia, which Cavalier King Charles spaniels are also prone to (see syringomyelia), and it is difficult to know, without MRI scans, to what extent these signs are due to syringomyelia or primary secretory otitis media (Rusbridge et al 2000, Lu et al 2003, Hayes et al 2010).

2. Intensity of welfare impact    

The welfare problems attributed to PSOM by Stern-Sertholtz et al (2003) are often severe: 39/61 (64%) of dogs with the condition that they examined were in pain. Other welfare problems ascribed to this condition are difficulties with walking and itchiness.

3. Duration of welfare impact

Primary secretory otitis media mostly affects dogs in middle age, although Stern-Sertholtz et al (2003) recorded seeing cases in animals from 2-10 years of age. Without treatment the signs tend to worsen. Treatment is likely to be effective in relieving the clinical problems but involves veterinary visits and anaesthetics (often repeated) which may themselves have adverse welfare effects (Cox et al 1989, Stern-Sertholtz et al 2003, Corfield et al 2008).

4. Number of animals affected

Whilst scanning dogs to determine whether they have the condition syringomyelia, material has been observed in the middle ear of CKCSs. Between 28 and 54% of these dogs (which may not be representative of the whole population) were found to have this material present (Lu et al 2003, Owen et al 2004, Hayes et al 2010). Owen et al (2004) found that CKCSs were particularly predisposed to the problem. We are unaware of any data on the prevalence in the CKCS population as a whole.

5. Diagnosis

Diagnosis is not straightforward. The disease is in the middle ear, a part of the body that is not directly visible. Advanced imaging techniques are needed to identify the condition. When fluid in the middle ear presses on the eardrum, which is painful, it may cause the eardrum to bulge outwards, and this may be visible to a veterinary surgeon examining the ear with an otoscope or a video otoscope. Radiographs of the middle ear may sometimes be helpful in diagnosis but the most reliable method is magnetic resonance imaging (MRI). Hearing tests, for example BAER testing (brainstem auditory evoked responses), can also be useful (Munro & Cox 1997).

6. Genetics

The genetic basis of this condition has not been investigated. It seems likely that multiple genes are involved.

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

It is currently not possible to identify animals likely to become affected but since the condition is reported to be very common in CKCS there is a chance that any animal will become affected. It is not known if carrier animals exist.

8. Methods and prospects for elimination of the problem

In order to reduce the prevalence of PSOM, affected individuals should not be used for breeding. Nor, ideally, based on general principles regarding tackling polygenetic conditions (Bell 2010), should those with a close relative that has had the disease been bred from either. 


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1. Clinical and pathological effects

The middle ear is an air-filled bony cavity that connects the external ear canal at the eardrum (tympanum) to the inner ear, which contains the organs of hearing and balance. Glands in the lining of the middle ear normally produce small amounts of mucus which drains, via the Eustachian canal, into the back of the mouth (the nasopharynx) (Macy 1989).

In Cavalier King Charles spaniels affected with primary secretory otitis media this mucus fails to drain away (Stern-Sertholtz et al 2003, Hayes et al 2010). The reason for this appears to be related to the abnormally thick soft palate seen at the back of the mouth in many dogs of this breed – and, which is due to brachycephaly, the abnormal short head shape that has been selected for in this and other brachycephalic breeds. In these dogs, although the bone structure of the muzzle is shortened, the soft tissues within it are not correspondingly altered in size and are therefore disproportionately large (Hayes et al 2010). It is also possible that the mucus produced is abnormal in these dogs, and may be thicker so that it does not drain normally. This is seen in humans with the condition ‘glue ear’ (Meyer 1976).

The abnormal accumulation of mucoid fluid within the middle ear may cause pain by pressing on the surrounding structures (Stern-Sertholtz et al 2003, Cole 2007). Many affected dogs do not, however, show obvious clinical signs of the condition (Hayes et al 2010). Clinical signs of the disease that have been reported include: pain in the head and neck, which can show through an abnormal carriage of the head - with the head held in a tilted position or horizontally; ataxia (unsteadiness when walking), facial nerve damage, nystagmus (uncontrolled twitching of the eyes), seizures, itching around the ears, inflammation of the external ear canal (otitis externa), fatigue, and varying degrees of deafness (Stern-Sertholtz et al 2003). However, subsequent to this study that reported PSOM, the serious and painful condition syringomyelia (see this website - https://www.ufaw.org.uk/syring.php) has been found to be very common in CKCS and it is currently unclear the degree to which the clinical signs mentioned above can be attributed solely to PSOM or to underlying syringomyelia (Rusbridge et al 2000, Lu et al 2003, Hayes et al 2010).

Most dogs reported to have clinical signs of PSOM respond successfully to treatment. In this, the mucus is removed and the middle ear is flushed out, sometimes repeatedly, or a device to aid drainage - a grommet – is placed in the ear drum (Cox et al 1989, Stern-Sertholtz et al 2003, Corfield et al 2008). That this treatment is effective suggests that the condition is significant in itself, as well as being a complication in the diagnosis of syringomyelia and other neurological diseases common in this breed (Rusbridge et al 2000, Rusbridge 2003, Rusbridge 2004). The condition of syringomyelia is difficult to treat and some CKCS owners may not pursue efforts to diagnosis this, if the signs of the much more readily treatable PSOM are mistakenly confused with those of syringomyelia (Cole 2007).

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2. Intensity of welfare impact

The welfare problems attributed to PSOM by Stern-Sertholtz et al (2003) are often severe: 39/61 (64%) of dogs with the condition that they examined were in pain. Other welfare problems ascribed to this condition are difficulties with walking and itchiness.

The welfare problems attributed to PSOM by Stern-Sertholtz et al (2003) are often severe: 39/61 (64%) of the dogs with the condition that they examined were in pain. However, as outlined above, there is some doubt about this as the signs shown by some of these dogs may have been due to undiagnosed syringomyelia rather than PSOM (Rusbridge et al 2000, Rusbridge 2004, Hayes et al 2010). Nevertheless, there remains strong evidence that PSOM causes significant pain in many affected dogs and leads to other diseases that cause welfare problems, by affecting nerve functions resulting in difficulty in walking and extreme itchiness.

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3. Duration of welfare impact

PSOM mostly affects dogs in middle age, although Stern-Sertholtz et al (2003) reported cases in dogs from 2-10 years of age. Unless successfully treated, the signs tend to worsen. Treatment is likely to be effective but involves veterinary visits and anaesthetics (often repeated) which may themselves have adverse welfare effects (Cox et al 1989, Stern-Sertholtz et al 2003, Corfield et al 2008).  

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4. Number of animals affected

Whilst scanning dogs to determine whether they have the condition syringomyelia, material has been observed in the middle ear of CKCSs. Between 28 and 54% of these dogs (which may not be representative of the whole population) were found to have this material present (Lu et al 2003, Owen et al 2004, Hayes et al 2010). Owen et al (2004) found that CKCSs were particularly predisposed to the problem. We are unaware of any data on the prevalence in the CKCS population as a whole.

From data on estimates of the total dog population in the UK and on the percentage of all micro-chip registered dogs that are Cavalier King Charles spaniels (Lucy Asher 2011, personal communication), we estimate that the UK population size of this breed may be around 200,000.

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5. Diagnosis

Diagnosis is not straightforward. The disease is in the middle ear, a part of the body that is not directly visible. Advanced imaging techniques are needed to identify the condition. When fluid in the middle ear presses on the eardrum, which is painful, it may cause the ear drum to bulge outwards, and this may be visible to a veterinary surgeon examining the ear with an otoscope or a video otoscope. Radiographs of the middle ear may sometimes be helpful in diagnosis but the most reliable method is magnetic resonance imaging (MRI). Hearing tests, for example BAER testing (brainstem auditory evoked responses), can also be useful (Munro & Cox 1997).

The disease may be suspected in dogs showing the clinical signs outlined above but these signs overlap considerably with those that occur with syringomyelia, which is another common and serious disease of CCKSs. Differentiating between PSOM and syringomyelia requires MRI scanning. Some dogs will have both conditions.

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6. Genetics

The pathology and cause of this condition has not been fully elucidated but it is to some degree associated with brachycephalic head shape. Brachycephaly has long been thought to be the result of an inherited defect (Stockard 1941). Recently, the region of the canine genome associated with brachycephaly has been identified and 2 genes have been implicated but exactly which gene or genes are involved remains unclear at present (Bannasch et al 2010). Not all brachycephalic breeds are predisposed to PSOM and so it is likely that other genetic influences are also involved in the condition in CKCS. That Cocker spaniels, a breed related to CKCSs, also seem to be predisposed to PSOM gives further credence to this possibility (Owen et al 2004).  

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

It is currently not possible to identify animals likely to become affected but, since the condition is reported to be very common in CKCS, there is a good chance that any particular animal is likely to become affected. It is not known if carrier animals exist.

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8. Methods and prospects for elimination of the problem

In order to reduce the prevalence of PSOM, affected individuals should not be used for breeding. Nor, ideally, based on general principles regarding tackling polygenetic conditions (Bell 2010), should those with a close relative that has had the disease.  However, in selective breeding to try to tackle this disease, care will have to be taken to avoid unintentionally increasing the prevalence of other diseases. If animals with PSOM are excluded from the breeding population this could narrow the gene pool and have unintended and undesirable genetic consequences (Oberbauer 2005). In breeds, such as the CKCS, with several serious genetic welfare problems the solution may be to outbreed with dogs of breeds that do not have these diseases.

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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

Bannasch D, Young A, Myers J, Truvé K, Dickinson P, Gregg J, Davis R, Bongcam-Rudloff E, Webster MT, Lindblad-Toh K and Pedersen N (2010) Localization of Canine Brachycephaly Using an Across Breed Mapping Approach. PLoS ONE 5(3): e9632. doi:10.1371/journal.pone.0009632

Bell JS (2010) Genetic Testing and Genetic Counseling in Pet and Breeding Dogs. 35th World Small Animal Veterinary Association World Congress Proceedings. 2-5th June 2010, Geneva, Switzerland. http://www.vin.com/Members/Proceedings/Proceedings.plx?CID=wsava2010&PID=pr56159&O=VIN accessed 14.7.2011

Cole L (2007) Primary Secretory Otitis Media in the Cavalier King Charles Spaniel (PT13). Western Veterinary Conference February 18th-22nd Las Vegas, Nevada http://www.vin.com/Members/Proceedings/Proceedings.plx?CID=wvc2007&PID=pr15090&O=VIN accessed 2.9.2011

Corfield G, Burrows A, Imani P and Bryden S (2008) The method of application and short term results of tympanostomy tubes for the treatment of primary secretory otitis media in three Cavalier King Charles Spaniel dogs. Australian Veterinary Journal 86: 88–94

Cox CL, Slack RWT and Cox GJ (1989) Insertion of a transtympanic ventilation tube for the treatment of otitis media with effusion. Journal of Small Animal Practice 30: 517–519

Hayes GM, Friend EJ and Jeffery ND (2010) Relationship between pharyngeal conformation and otitis media with effusion in Cavalier King Charles spaniels. Veterinary Record 167: 55-8

Lu D, Lamb CR, Pfeiffer DU and Targett MR (2003) Neurological signs and results of magnetic resonance imaging in 40 cavalier King Charles spaniels with Chiari type 1-like Malformations. Veterinary Record 153: 260-263

Macy DW (1989) Diseases of the ear. In: Textbook of Veterinary Internal Medicine, 3rd edn. Editor SJ Ettinger. WB Saunders, Philadelphia pp 258

Meyer FA (1976) Mucus structure: relation to biological transport function. Biorheology 13: 49-58

Munro KJ and Cox CL (1997) Investigation of hearing impairment in Cavalier King Charles spaniels using auditory brainstem response audiometry. Journal of Small Animal Practice 38: 2–5

Oberbauer A (2005) Strategies for Identifying and Managing Complex Genetic Disorders. Tufts’ Canine and Feline Breeding and Genetics Conference, Sturbridge, Massachusetts September 30 – October 1, 2005 http://www.vin.com/Members/Proceedings/Proceedings.plx?CID=tuftsbg2005&PID=pr10628&O=VIN accessed 6.9.2011

Owen MC, Lamb CR, Lu D and Targett MP (2004) Material in the middle ear of dogs having magnetic resonance imaging for investigation of neurologic signs. Veterinary Radiology and Ultrasound 45: 149-155

Rusbridge C (2003) Neurological diseases of the Cavalier King Charles spaniel. Journal of Small Animal Practice 46: 265–272

Rusbridge C (2004) Primary secretory otitis media in Cavalier King Charles spaniels. Journal of Small Animal Practice 45: 222; author reply 222

Rusbridge C, Macsweeny J, Davies JE, Chandler JV, Fitzmaurice KV, Dennis SN, Cappello R and Wheeler SJ (2000) Syringomyelia in cavalier King Charles spaniels. Journal of the American Animal Hospital Association 36: 34-41

Stern-Sertholtz W, Sjöström L and Hårkanson NW (2003) Primary secretory otitis media in the Cavalier King Charles spaniel: a review of 61 cases. Journal of Small Animal Practice 44: 253–256

Stockard CR (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.

© 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