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.
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.
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).
For further details about this condition, please click on the following:
- Clinical and pathological effects
- Intensity of welfare impact
- Duration of welfare impact
- Number of animals affected
- How do you know if an animal is a carrier or likely to become affected?
- Methods and prospects for elimination of the problem
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.
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).
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.
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.
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).
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.
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.
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.
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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http://www.thekennelclub.org.uk/item/113 accessed 17th February 2011.
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