Genetic welfare problems of companion animals

 

Otitis Externa and Media

 

Breed: Cocker Spaniel

 

Condition:  Otitis Externa and Media

Related terms: ear infection

Outline: Otitis externa is inflammation of the ear canal. It is common and can become severe and chronic in cocker spaniels. It is thought that the breed is predisposed to the condition because of several ear abnormalities including the long, drooping ears, characteristic of the breed, and excessive hair growth and wax production within the ear canals. Otitis externa causes discomfort, irritation and pain and can persist or progress throughout life. Medical resolution can be difficult and severe cases may require major surgery to remove the outer wall of the ear or to remove the ear canal completely.

 


 

Summary of Information

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1.           Brief description

Otitis externa (OE) is inflammation of the external ear canal often accompanied with irritation which may cause the affected dog to shake its head, rub the ear with a paw or against the floor or furniture, scratch at it with a hind leg. In some cases the ear may be painful, with the dog crying as it scratches at it. This pain may cause the dog to guard the ear and show aggression when the ear is touched, or may cause decreased activity and appetite. There may be waxy, pusy or bloody discharge.

Many factors influence the health of the ear canal. Conventionally, these factors have been categorised into three types: primary factors that cause otitis externa in any individual; predisposing factors that tend to increase susceptibility to otitis externa but which do not, by themselves, cause the disease, and perpetuating factors which only contribute to the disease when it has been triggered by other factors but which themselves also require control in order to treat the condition (August 1988).


It has been suggested that the high incidence of OE in Cocker spaniels is due partly to the pendulous ears characteristic of the breed, excessive hair in the ear canal that traps wax and scale, the relatively narrow ear canals, a greater density of glands in the skin of their ear canal (Harvey 2009), and the Cocker spaniels’ predispositions to atopy, hypothyroidism and idiopathic seborrhoea.


These factors contribute to causing an abnormally reduced air flow in the ear canal with greater humidity, reduced acidity and increased susceptibility to infections. Infections can be caused by  over-growth of the normal ear canal flora eg by the Staphylococcal bacteria and Malassezia yeasts normally found in the ear canal, or by bacteria that are not normally present in the ear. The most serious infections, both in terms of the pain and distress that they cause and the difficulty of treatment are those caused by Gram-negative bacteria of the Pseudomonas species (Harvey et al 2001).


Inflammation of the ear canal results in increased thickness of the ear canal’s wall from scarring and, sometimes, from calcification and thickening of the outer layer of the skin (hyperkeratosis), and increased growth  of skin glands and their waxy secretions. These further narrow the ear canal and this perpetuates an environment that encourages microbial growth such that repeated infections are likely.


Cocker spaniels seem to develop a characteristic form of otitis externa that differs from that seen in other breeds (Angus et al 2002). In this ceruminous otitis externa, there is a marked expansion of the ceruminous (wax producing) glands.


As chronic otitis externa progresses, any associated infection commonly spreads, in time, through the ear drum to affect the middle ear (otitis media). Unless this is controlled, it prevents the resolution of otitis externa.


Treatment of otitis externa is based on the control or elimination of predisposing and primary factors when possible and appropriate medical treatment for any perpetuating factors. In chronic cases, major surgery to remove the ear canal and the outside section of the middle ear (total ear canal ablation with lateral bulla osteotomy) may be the only option (
Mason et al 1988).

 

 

2.           Intensity of welfare impact             

Otitis externa causes long-term, frequently recurrent episodes of discomfort and pain (Asher et al 2009). Veterinary interventions may help (Nuttall et al 2009) but in Cocker spaniels these often need to be prolonged and repeated. Dogs with chronically thickened and narrowed ear canals may require major surgery to control the disease and tackle the chronic pain (Harvey et al 2001). Infection may spread to the middle ear, which also often results in obvious pain and can cause long lasting damage (Stern-Bertholtz et al 2003).

 

3.           Duration of welfare impact

 

Most affected dogs have life-long recurrent pain and discomfort once otitis externa starts. Once the chronic stages with thickened walls and narrowing of the ear canal become established the effects usually worsen and the dog will be affected for the rest of its life.

 

4.           Number of animals affected

 

Cocker spaniels are predisposed to otitis externa (Fraser et al 1961, Fraser 1965, Rycroft and Sabam 1977, Scott et al 1995, Cristina and Degi 2007, Saridomichelakis et al 2007, Nuttall et al 2009) but as far as we aware, data on the proportion of individuals that develop the disease is unknown. Of 100 dogs presented to Saridomichelakis et al (2007) for treatment of otitis externa, 18% were cocker spaniels. It is generally recognised that dogs of this breed are predisposed to severe otitis externa and otitis media severe enough to require surgical treatment. In one study of surgical ear canal removal to treat such cases, 48 out of 80 dogs (60%) were Cocker spaniels (Angus et al 2002). From data on estimates of total dog population in the UK and on the percentage of all micro-chip registered dogs that are Cocker spaniels (Lucy Asher, 2011, personal communication), we estimate that the UK population size of this breed may be around 350,000.

 

5.           Diagnosis

The presence of otitis externa is usually obvious to the owner as the dog shows signs of pain and irritation in its ears and they are often dirty and smelly. Veterinary investigations are needed to elucidate the underlying factors, the extent of the problem and the type of any infection present. Investigations often have to be repeated as the condition persists.

 

6.           Genetics

 

The genes involved in the predisposition of Cocker spaniels to otitis externa are unknown. It is likely that multiple genes and environmental influences are involved. The characteristic drooping ears which are a factor predisposing the dogs to this disease clearly have a genetic basis and are part of the breed standard.


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

Dogs of this breed are at risk of this disease partly because of the conformation of the ears. As far as we are aware there is no way of predicting which puppies will become severely affected.

 

8.          Methods and prospects for elimination of the problem

 

It seems likely that the condition will be perpetuated unless there is selection against it, and sensible to advise that animals with severe chronic otitis externa, or those that have close relatives with the condition, should not be used for breeding (Bell 2010).

 

 

 


 

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1.           Clinical and pathological effects

 

Otitis externa (OE) is inflammation of the external ear canal – the tube of cartilage and skin that extends from the ear flap (pinna) down to the ear drum. On the inside of the ear drum is the middle ear and, in more severe cases of otitis externa, the ear drum can rupture and an infection spread into the middle ear.

The ear canal is lined with skin and can be affected by diseases similar to those that affect skin elsewhere on the body. In otitis externa there is inflammation with accompanying irritation which may cause the affected dog to shake its head, rub the ear with a paw or against the floor or furniture, scratch at it with a hind leg. In some cases the ear may be painful, with the dog crying as it scratches at it. This pain may cause the dog to guard the ear and show aggression when the ear is touched, or may cause decreased activity and appetite. There may be waxy, pusy or bloody discharge.


Otitis externa is a complex condition. Many factors affect  the ecology and health of the ear canal. Conventionally these factors have been categorised into three types: primary factors that cause otitis externa in any individual; predisposing factors that tend to increase susceptibility to otitis externa but which do not, by themselves, cause the disease, and perpetuating factors which only contribute to the disease when it has been triggered by other factors but which themselves also require control in order to treat the condition (August 1988). Examples of common primary, predisposing and perpetuating factors (
Griffin 1993) are listed below.

 

Predisposing factors: narrow ear canals, pendulous ears, excessive hair growing in the ear canal, repeated wetting e.g. from swimming, or exudates from neoplasms or polyps.

Primary factors: the presence of ear mites  (Otodectes cyanotis), neoplasia, polyps, foreign bodies (eg grass seeds), irritation caused bydrugs or chemicals, allergies and hypersensitivities, primary seborrhoea (see below), excessive skin gland secretions, and hormonal diseases such as hypothyroidism.

Perpetuating factors: excessive proliferation of bacteria and yeasts normally found on the skin, infections from abnormal bacteria especially Pseudomonas, chronic inflammation, and otitis media. Fraser (1965) reported that at least 59% of dogs with chronic otitis externa were also suffering from skin disease elsewhere on their bodies.


Otitis externa is common in Cocker spaniels and this is thought to be related to several factors (Fraser et al 1961, Fraser 1965, Rycroft and Sabam 1977) as outlined below.

1) The pendulous (droopy) ears characteristic of the breed are a predisposing factor for OE (Baxter and Lawler 1972, Hayes et al 1987).

2) All dogs have hair growing in their ear canals but Cocker spaniels have more than normal because each of their hair follicles produces several hairs (Fraser 1965, Stout-Graham et al 1990). As a result, wax and scale tends to be trapped in the ear canal, air flow reduced and humidity increased promoting the growth of microorganisms.

3) Some individuals may have narrower ear canals, but it is not clear if this is inherited (Stout-Graham et al 1990). It may be due to their having more soft tissue and more wax producing glands in the skin of the ear canal (Harvey 2009).

4) Otitis externa occurs more commonly in dogs with skin abnormalities including allergic skin disease (reactions to foods), keratinisation diseases (in which the surface of the skin develops abnormally resulting in scaly, greasy skin (primary seborrhoea), some hormonal diseases (e.g. hypothyroidism) or autoimmune diseases. In fact, skin allergy (atopy) is the most common cause of otitis externa and most dogs with skin allergy get otitis externa at some point (Harvey et al 2001). Susceptibility to these conditions may be inherited and Cocker spaniels are known to be predisposed to two important primary causes of otitis externa – atopy (Saridomichelakis et al 1999, Nuttall et al 2009) and primary seborrhoea (Kwochka and Rademakers 1989). Older Cocker spaniels are also predisposed to hypothyroidism, which is an additional primary factor (Milne and Hayes 1981).


In the study by Saridomichelakis et al (2007) 44% of the Cocker spaniels treated for otitis externa were found to have atopy.


These factors all tend to result in increased humidity in the ear canal. Secretions within the ear also tend to become less acidic and as a result of these changes in the habitat of the ear canal, infections tend to occur. These can be due to over-growth of organisms of the normal ear canal flora (Staphylococci bacteria and Malassezia yeasts) or to infection with bacteria that are not normally present. The most serious infections, in terms both of the pain and distress that they cause and of the difficulty in treating them are caused by the Gram-negative bacterium, Pseudomonas (Harvey et al 2001). Cocker spaniels are predisposed to Pseudomonas otitis externa (Fraser 1961, Grono and Frost 1969). Gram-negative bacterial infections of the ear canal often progress to a rupturing of the eardrum and spread of infection into the middle ear (Saridomichelakis et al 2007).


Inflammation of the ear canal causes scarring and, sometimes, calcification and thickening of the outer layer of the skin and growth of the wax-producing glands. This leads to increased thickness of the ear canal wall and the canal’s narrowing. This perpetuates the conditions within the ear that encourage microbial growth and so repeated infections are likely, despite short-term medical treatment being effective (Harvey et al 2001).


Cocker spaniels seem to develop a characteristic form of otitis externa with marked expansion of the wax-producing glands (Angus et al,2002). In chronic otitis externa, any associated infection usually spreads through the eardrum to affect the middle ear (resulting in otitis media). In one study 61% of Cocker spaniels with otitis externa were found to have otitis media also. (Saridomichelakis et al, 2007). Around 80% of dogs with chronic otitis externa get middle-ear disease (
Griffin 1993).


In some cases, such infection may spread further to involve the inner ear. This can damage the mechanisms that enable the animal to balance correctly and can also lead to deafness. Loss of hearing can also occur when the ear canal is obstructed in chronic otitis externa and media (and as a consequence of surgery to control otitis externa and media (see below) (Strain 1996). Occasionally infection may spread into the bloodstream causing generalised and serious disease. Sometimes there is damage to nerves that run through the middle ear resulting in facial paralysis or decreased tear production.


Treatment of otitis externa is based on the control and elimination of predisposing and primary factors, when possible, and on appropriate medical treatment to tackle perpetuating factors (that lead to narrowing of the ear canal).  When control of the perpetuating factors becomes impossible due to the thickness of the ear canal wall and its narrowness then major surgery is the only option. Removal of the ear canal and the outside section of the middle ear (total ear canal ablation with lateral bulla osteotomy) is the standard surgery for this (
Mason et al 1988). This is considered major surgery, with a significant possibility of side effects from post-surgical wound infections and from the possibility of damage to nerves that run through the middle ear (Mason et al 1988, Fossum et al 1997). In some situations, when it is predicted that chronic otitis externa is going to be a significant welfare problem for the dog, it has been suggested that it may be better to perform surgery before otitis media and severe disease in the lower ear canal develop. This is because the surgery required at this stage is less radical.  Vertical wall ablation, in which the external side of the vertical part of the ear canal is removed, opening the side of the ear canal to the air and enabling better access to the deeper part of canal is used to control otitis externa (Harvey 2009).


It has been suggested that cocker spaniels are also predisposed to parasitic otitis externa caused by the ear mite Otodectes cyanotis (
Cristina and Degi 2007), but this may not be a significant factor in the development of chronic otitis externa in many cases.


Cocker spaniels are also predisposed to otitis externa due to grass seed foreign bodies becoming lodged in an ear canal (Saridomichelakis et al 2007). This may be associated with the abnormal, pendulous conformation of their ears. Such foreign bodies cause severe irritation and sometimes painful otitis externa. Secondary infection can occur. This form of otitis is readily treatable and it only affects animals allowed to run in mature grasslands.

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2.               Intensity of welfare impact

Otitis externa causes long-term, frequently recurrent episodes of discomfort and pain (Asher et al 2009). Veterinary interventions may help (Nuttall et al 2009) but in Cocker spaniels these often need to be prolonged and repeated. Dogs with chronically thickened ear canal walls and narrowed ear canals may require major surgery to control the disease and tackle the chronic pain (Harvey et al 2001). Infection often spreads into the middle ear causing otitis media which is also often obviously painful (Stern-Bertholtz et al 2003).


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3.           Duration of welfare impact

 

Once the chronic changes of thickened ear canal wall and narrowed ear canal become established the condition usually worsens and the dog will be affected for the rest of its life. Saridomichelakis et al (2007) studied dogs presented to a veterinary hospital for otitis externa (both first and second opinion cases). The average age of the dogs seen was between four and five years and most already had long-standing ear problems. Similarly, Cristina and Degi (2007) found that otitis externa was most often seen in dogs between the ages of two and five. Affected dogs will probably be uncomfortable all the time and discomfort is shown by rubbing and scratching the ears and shaking of the head. Episodes of more serious infection and pain tend to occur and in many dogs these episodes will occur at increasing frequency. At some stage they can prevented only by major surgery. The surgery itself is likely to have a significant welfare impact as a result of pain and discomfort. Most affected dogs have life-long welfare problems once otitis externa starts.



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4.           Number of animals affected

 

Ear and skin diseases are the second most common type of problem in dogs (Lund et al 1999) and in one study in the UK, ear disease was found to be the most commonly diagnosed skin problem (Hill et al 2006). Ear disease is the most common reason for veterinary consultations, making up about 5-25% of all veterinary consults (Evans et al 1974).

Cocker spaniels are predisposed to otitis externa (Fraser et al 1961, Fraser 1965, Rycroft and Sabam 1977, Scott et al 1995, Cristina and Degi 2007, Saridomichelakis et al 2007, Nuttall et al 2009) but we are unaware of data on the proportion of individuals that develop the disease. Of 100 dogs presented to Saridomichelakis et al (2007) for treatment of otitis externa, 18% were Cocker spaniels. It is generally recognised that dogs of this breed are predisposed to severe otitis externa and otitis media bad enough to require surgical treatment. In one study of surgical ear canal removal to treat such cases, 48 out of 80 dogs (60%) were Cocker spaniels (Angus et al 2002). :  From data on estimates of total dog population in the UK and on the percentage of all micro-chip registered dogs that are Cocker spaniels (Lucy Asher, 2011, personal communication), we estimate that the UK population size of this breed may be around 350,000.


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5.           Diagnosis

 

The condition is usually diagnosed by an owner noticing signs of ear irritation (scratching or rubbing the ears), a pain response on touching an infected ear or by noticing a bad smell from the ear. Some dogs with otitis externa have a head tilt (Scott et al 1995).


Otitis media may be hidden but may lead to repeated bouts of otitis externa. Other signs seen in some dogs with otitis media are a head tilt, facial spasm or paralysis on one side, decreased tear production and dry eye (keratoconjunctivitis sicca) and other signs of nerve damage (eg Horner’s syndrome). Veterinary examination confirms the diagnosis of otitis externa but determining the predisposing, primary and perpetuating factors is a more difficult and involved process, It may require microscopic and microbiological examinations of material obtained from the ear, inspection  under anaesthetic, perhaps using an endoscope and imaging of the middle ear using x-rays or
MRI (magnetic resonance imaging) (Cole et al 2002). The perpetuating factors will vary from one presentation to the next so diagnosis of these often has to be repeatedly performed, whilst managing the otitis externa over months or years (Nuttall et al 2009).

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6.           Genetics

The genes involved in the predisposition of Cocker spaniels to otitis externa are unknown. As outlined above a variety of conformational and other factors (pendulous ears, voluminous wax production, compound hair follicles, atopy, idiopathic seborrhoea) may contribute so it is likely that many genes are involved.

 

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

Dogs of this breed are at risk of this disease partly because of the conformation of the ears and because of other predisposing factors as outlined above. As far as we are aware there is no way of predicting which puppies will become severely affected.


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8.          Methods and prospects for elimination of the problem

It seems likely that the condition will be perpetuated unless there is selection against it, and sensible to advise that animals with severe chronic otitis externa, or those that have close relatives with the condition, should not be used for breeding (Bell 2010).

Otitis externa is only one of several significant genetic welfare problems in the Cocker spaniel. Choice of breeding animals should include consideration of all these conditions.

 

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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 and to Dr James Yeates for his contribution.

 

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10.          References

Angus JC, Lichtensteiger C, Campbell KL and Schaeffer DJ (2002) Breed variation in histopathologic features of chronic severe otitis externa in dogs: 80 cases (1995–2001). Journal of the American Veterinary Medical Association 221: 1000–6

Asher l, Diesel G, Summers JF, McGreevy PG and Collins LM (2009) Inherited defects in pedigree dogs I: conforming to standards. The Veterinary Journal 182: 402-11


August JC (1988) Otitis externa. A disease of multifactorial etiology. Veterinary Clinics of North America-Small Animal Practice 18: 731–42


Baxter M and Lawler DC (1972)
The incidence and microbiology of otitis externa of dogs and cats in New Zealand. New Zealand Veterinary Journal 20: 29-32


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

 

Cole LK, Kwochka KW, Podell M, Hillier A and Smeak DD (2002) Evaluation of radiography, otoscopy, pneumotoscopy, impedance audiometry and endoscopy for the diagnosis of middle-ear disease in the dog. In: Advances in Veterinary Dermatology, Vol 4 (Proceedings of the Fourth World Congress of Veterinary Dermatology) edited by KL Thoday, CS Foil and R Bond. Blackwell Science: Oxford. pp 49

Cristina RT and Dégi J (2007) Studies on Otitis Externa in Dogs. 17th Congress of the European College of Veterinary Internal Medicine-Companion Animals

 

Evans JM, Lane DR and Hendy PG (1974) The profile of small animal practice. Journal of Small Animal Practice 15: 595-607

Fossum TW, Hedlund CS, Hulse DA, Johnson AL, Seim HB III, Willard MD and Carroll GL (1997) Surgery of the ear. In: Small Animal Surgery. Mosby, St Louis pp 163


Fraser G (1965)
Aetiology of otitis externa in the dog. Journal of Small Animal Practice 6: 445–451

Fraser G, Withers AR and Spreull JSA (1961) Otitis Externa in the Dog. Journal of Small Animal Practice 2: 32–47

Griffin CE (1993) Otitis externa and middle-ear disease. In: Current Veterinary Dermatology: The Science and the Art of Therapy. Edited by CE Griffin, KW Kwochka and JM MacDonald. Mosby Year Book, St Louis. pp 245

 

Grono LR and Frost AJ (1969) Otitis externa in the dog: the microbiology of the normal and affected external ear canal. Australian Veterinary Journal 45: 420–422

 

Harvey RG (2009) Predisposing, Primary and Perpetuating Factors of Otitis. Proceeding of British Small Animal Veterinary Congress 255-6

 

Harvey RG, Harari J and Delauche AJ (2001) Ear Disease of the Dog and Cat. Manson Publishing Ltd, London. pp 83

 

Hayes HM Jr, Pickle LW and Wilson GP (1987) The effects of ear type and weather on the hospital prevalence of canine otitis externa. Research in Veterinary Science 42: 294-298

 

Hill PB, Lo A, Eden CAN, Huntley S, Morey V, Ramsey S, Richardson C, Smith DJ, Sutton C, Taylor MD, Thorpe E, Tidmarsh E and Williams V (2006) Survey of the prevalence, diagnosis and treatment of dermatological conditions in small animals in general practice. Veterinary Record 158: 533-539

 

Kwochka KW and Rademaker AM (1989) Cell proliferation kinetics of epidermis, hair follicles and sebaceous glands of cocker spaniels with idiopathic seborrhoea. American Journal of Veterinary Research 50: 1918-1922

 

Lund EM, Armstrong PJ and Kirk CA (1999) Health status and population characteristics of dogs and cats examined at private veterinary practices in the United States. Journal of the American Veterinary Medical Association 214: 1336-1341

 

Mason LK, Harvey CE and Orsher RJ (1988) Total Ear Canal Ablation Combined with Lateral Bulla Osteotomy for End-Stage Otitis in Dogs Results in Thirty Dogs. Veterinary Surgery 17: 263–268

 

Milne KL and Hayes HM (1981) Epidemiological features of canine hypothyroidism. The Cornell Veterinarian 71: 3-14

 

Nuttall T, Harvey RG and McKeever PJ (2009) Canine atopic dermatitis. In: Skin Diseases of the Dog and Cat. Manson Publishing Ltd pp 20

 

Rycroft AK and Saben HS (1977) A clinical study of otitis externa in the dog. Canadian Veterinary Journal 18: 64–70

Saridomichelakis MN, Farmaki R, Leonidas LS and Koutinas AF (2007) Aetiology of canine otitis externa: a retrospective study of 100 cases. Veterinary Dermatology 18: 341–347

Saridomichelakis MN, Koutinas AF and Gioulekas D (1999) Canine atopic dermatitis in Greece: clinical observations and the prevalence of positive intradermal test reactions in 91 spontaneous cases. Veterinary Immunology and Immunopathology 1999; 69: 61–73

 

Scott DW, Miller MH and Griffin CE (1995) In: Muller and Kirk’s Small Animal Dermatology 5th edition WB Saunders, Philadelphia pp 66

 

Scott DW and Paradis M (1990) A survey of canine and feline skin disorders seen in a university practice: Small Animal Clinic, University of Montreal, Saint-Hyacinthe, Quebec (1987-1988). Canadian Veterinary Journal 31: 830-835

Stern-Bertholtz W, Sjöström I and Wallin Håkanson N (2003) Primary secretory otitis media in the Cavalier King Charles spaniel: a review of 61 cases. Journal of Small Animal Practice 44: 253–256

 

Strain GM (1996) Aetiology, prevalence and diagnosis of deafness in dogs and cats. British Veterinary Journal 152: 17

 

Stout-Graham M, Kainer RA, Whalen LR and Macy DW (1990) Morphometric measurements of the external ear canal of dogs. Journal of Veterinary Research 51: 990–4

http://www.thekennelclub.org.uk/item/113 accessed 17th February 2011.

 

 

 

 

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