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Q: Are dogs with hanging ears more likely to get ear infections?
A: Otitis externa is an infection of the ear canal that is, in most cases, able to be resolved with treatment. In a small number of cases it can become chronic and may require surgical treatment and can infrequently lead to disfigurement and fatal complications. Reports of several surveys indicate that when pedigree dogs are grouped according whether they possess pendulous or erect ears, there is a higher incidence of otitis externa in the group with pendulous ears. The difference in incidence is in often in the range of 13 to 14% versus 5%.1,2 Otitis externa incidence, however, is most closely associated with particular breeds within each group (whether ears are hanging or erect), and is especially prevalent in Cocker Spaniels,1,3,4 Poodles,2,3,4 and German Shepherd Dogs.4 It has been suggested that a hanging ear increases humidity and so may promote the development of infection originating from a skin disorder or irritant.5
Q: Why do long-eared breeds have higher rates of ear infection?
A: Breeds such as Cocker Spaniels seem to be predisposed to otitis externa due to a greater density of apocrine glands and a predisposition to proliferative ceruminous gland hyperplasia (i.e., proliferation of cells) and ectasia (i.e., dilation or distension).6 This clustering of risk factors suggests the risk of otitis externa in pedigreed dogs must be considered on a breed-by-breed basis, and that grouping study samples by ear shape (as described in the answer to the question above) may not be justified. Ear and eye abnormalities are commonly linked to traits that may be selected for in a breed, such as an all or partially white, merle or spotted coat.7 Therefore, although it is widely believed that pendulous ears increase the risk of otitis externa, there is a lack of unconfounded evidence establishing and quantifying the strength of this link.
A comparison might be drawn to studies showing higher incidence of incontinence in docked breeds.8 Although there appears to be a correlation, it cannot be assumed that tail docking is the cause of incontinence because traditionally docked breeds have other confounding predisposing characteristics (e.g., larger overall body size). To demonstrate that hanging ears are a significant risk factor (in general and by breed), and that this risk is significantly reduced or eliminated by cropping, otherwise similar dogs having cropped and uncropped ears would need to be compared. It should also be noted that some people believe ear cropping itself is harmful in exposing the ear canal to water and irritants, potentially leading to deafness,9 however this belief may stem from a coincidental combination of a cropping tradition and a congenital defect in a breed.10
Q: What should be done for dogs at increased risk of ear infection?
A: No group deems high incidence of otitis externa a valid reason for advocating routine cropping of the ears of Cocker Spaniels or Poodles.11,12 Some breeds, such as the Dalmatian9 and the Anatolian Shepherd Dog13 (where erect ears are an AKC disqualification14) were historically cropped, but this tradition waned without apparent ill effects. Nor are traditionally cropped breeds among those with the highest incidence of otitis externa, even in countries where cropping is rare. Thus it cannot be assumed that ear cropping has a medical purpose unless this is in some way demonstrated. Other traits known to predispose a dog to ear/hearing problems and other defects are not discouraged by breed standards adopted in the United States (e.g., blue eyes in Dalmatians15) and may even be encouraged (e.g., white markings in Boxers).
Current veterinary opinion appears to be that ear conformation affects ventilation and may be a factor contributing to otitis externa incidence and severity. However, most dogs with hanging ears will not suffer from infections,16 and ear conformation is not considered to be a primary cause. The basis for this opinion includes the low incidence of otitis externa in many breeds with pendulous ears (e.g., Beagles, Setters6) and the presence of other directly causal factors in otitis-prone breeds.
It has also been suggested there is no single primary cause of otitis externa and that risk factors vary substantially by breed.6 In the future, it may be demonstrated that certain breeds benefit from prophylactic treatment; however this recommendation is unlikely to generalize to all breeds. Furthermore, the surgery commonly performed to avoid (re)occurrence of otitis externa aims to open the ear canal rather than reduce the pinna. In all of the scientific papers we reviewed the authors' recommendation was that at-risk dogs should be monitored and treated proactively in a way that addressed the primary cause—none of these papers identified ear conformation as the primary cause.
Q: What if ear cropping is not being done for health reasons?
A: There has been long-standing opposition to ear cropping for the purpose of altering appearance. For example the ASPCA requested removal of cropped ears from American Kennel Club breed standards in 1895,17 and a similar recommendation first appeared in AVMA policy in 1976. AVMA currently opposes ear cropping when done for cosmetic purposes,18 as do several other national veterinary associations (e.g., Canada,19 United Kingdom20).
REFERENCES
1. Baxter, M. Letter: Pityrosporum pachydermatis in pendulous and erect ears of dogs. New Zeal Vet J 1976;4:69.
2. Masuda A, Sukegawa T, Mizumoto TH et al. Study of lipid in the ear canal in canine otitis externa with Malassezia pachydermatis. J Vet Med Sci 2000;62: 1177-1182.
3. Fraser G. Aetiology of otitis externa in the dog. J Small Anim Practice 2008;6:445-451.
4. Fernández G, Barboza G, Villalobos A. Isolation and Identification of microorganisms present in 53 dogs suffering otitis externa . Rev Cient (Maracaibo) 2006;16;23-30.
5. Huesser H. Otitis externa of the dog. VM/SAC, Veterinary Medicine & Small Animal Clinician. Veterinary Pub. Co.: Chicago. 1922. p.463.
6. Angus JC, Lichtensteiger C, Campbell KL et al. Breed variations in histopathologic features of chronic severe otitis externa in dogs: 80 cases (1995-2001). J Am Vet Med Ass 2002;221:1000-1006.
7. Deol MS. The relationship between abnormalities of pigmentation and of the inner ear. Proc Roy Soc Lond A 1970;175:201-217.
8. Thrusfield P, Holt M. Association in bitches between breed, size, neutering and docking, and acquired urinary incontinence due to incompetence of the urethral sphincter mechanism. Vet Rec 1993;133:177-180.
9. Drury, WD. British Dogs, Their Points, Selection, and Show Preparation. L. U. Gill: London. 1903. pg. 377, 475.
10. FTG Hobday, J McCunn. Surgical diseases of the dog and cat: with chapters on anaesthetics and obstetrics. Bailliere, Tindall and Cox: London. 1906. p. 85
11. Busch TJ. Letter: Canine ear cropping. New Zeal Vet J 1983;31:205.
12. Smith BJ. Canine Anatomy. Blackwell: New Jersey. p.110.
13. Anatolian Shepherd dog: an ancient breed. Rangelands 1982;4:63-65.
14. Anatolian Shepherd dog breed standard. American Kennel Club: http://www.akc.org/breeds/anatolian_shepherd_dog/ Accessed January 2nd, 2008.
15. Strain GM. Aetilogy, prevalence and diagnosis of deafness in dogs and cats. Br Vet J 1996;152:17-36.
16. Rosser EJ. Causes of otitis externa. Vet Clin Small Anim 2004;34:459-468.
17. ASPCA. Cropping dogs' ears: important action of the American Kennel Club. Our Animal Friends: An Illustrated Monthly Magazine 1895:23;1-3.
18. Ear cropping and tail docking of dogs. American Veterinary Medical Association: http://www.avma.org/issues/policy/animal_welfare/tail_docking.asp accessed January 2nd, 2008.
19. CVMA Website Cosmetic Surgery: http://canadianveterinarians.net/ShowText.aspx?ResourceID=46 Accessed December 15, 2008
20. RCVS Website Your responsibilities to your patients: http://www.rcvs.org.uk/Templates/Internal.asp?NodeID=89720&int2ndParentNodeID=89717&int1stParentNodeID=89642 Accessed December 15, 2008
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Source: Staff research, AVMA Animal Welfare Division
Contact: Dr. Emily G. Patterson-Kane (800.248.2862, ext 6746) with questions or comments.
This information has been prepared as a service by the American Veterinary Medical Association. Redistribution is acceptable, but the document's original content and format must be maintained, and its source must be prominently identified.
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