Q: Are dogs with hanging ears more likely to get ear infections?
A: Otitis externa is an inflammation of the epithelium (lining) of the ear canals and surrounding structures; secondary bacterial colonization may occur.1 Otitis externa may be associated with other dermatologic diseases such as allergic or immune-mediated skin disease, or with systemic diseases.1 In most cases, it can be resolved with treatment; however, in some cases it can become chronic, may require surgical treatment and can infrequently lead to disfigurement and fatal complications. Several surveys indicate that when pedigreed dogs are grouped according to whether they possess pendulous or erect ears, the incidence of otitis externa is in the range of 13 to 14% versus 5%, respectively.2,3 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,2,4,5 Poodles,3,4,5 and German Shepherd Dogs.5 It has been suggested that a hanging ear or abundant hair in the ear canal increases humidity and so may promote the development of infection originating from a skin disorder or irritant.1,6
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).1,7 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 (e.g., pendulous or erect) 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.8 Therefore, although it is widely believed that pendulous ears increase the risk of otitis externa, there is a lack of strong scientific evidence establishing and quantifying the strength of this link.
A comparison might be drawn to studies showing higher incidence of incontinence in docked breeds.9 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 by exposing the ear canal to water and irritants, potentially leading to deafness,10 however this belief may stem from a coincidental combination of a cropping tradition and a congenital defect in a breed.11
Q: What should be done for dogs at increased risk of ear infection?
A: No group deems a high incidence of otitis externa a valid reason for advocating routine cropping of the ears of Cocker Spaniels or Poodles.12, 13 Some breeds, such as the Dalmatian10 and the Anatolian Shepherd Dog14 (where erect ears are an AKC disqualification15) were historically cropped, but this tradition waned without apparent detrimental effects. Nor are traditionally cropped breeds among those with the highest incidence of otitis externa, even in countries where cropping is rarely performed. Thus it cannot be assumed that ear cropping has a medical purpose. 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 Dalmatians16) 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 the incidence and severity of otitis externa. However, most dogs with hanging ears will not suffer from infections,17 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, Setters7) and the presence of other directly causal factors in otitis externa-prone breeds.
There appears to be no single primary cause of otitis externa and risk factors vary substantially by breed.7 In the future, it may be demonstrated that certain breeds benefit from prophylactic treatment; however this recommendation is unlikely to apply to all breeds. Furthermore, the surgery commonly performed to avoid (re)occurrence of otitis externa aims to open or remove the ear canal rather than reduce the pinna (ear flap). In all of the scientific papers 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 1895,18 and a similar recommendation first appeared in AVMA policy in 1976. The AVMA currently opposes ear cropping when done for cosmetic purposes,19 as do several other national veterinary associations (e.g., Canada,20 Australia21). The European Convention for the Protection of Pet Animals prohibits surgical operations (including ear cropping) for the purpose of modifying the appearance of a pet animal.22 In the United Kingdom no dog with cropped ears is eligible to compete at any Kennel Club licensed event23 and the procedure is prohibited by legislation in that country.
REFERENCES
1. Fossum TW. Surgery of the ear. In: Fossum TW, ed. Small Animal Surgery. 3rd ed. St.Louis; Mosby Elsevier, 2007;289-316.
2. Baxter, M. Letter: Pityrosporum pachydermatis in pendulous and erect ears of dogs. New Zeal Vet J 1976;4:69.
3. 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.
4. Fraser G. Aetiology of otitis externa in the dog. J Small Anim Practice 2008;6:445-451.
5. 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.
6. Huesser H. Otitis externa of the dog. VM/SAC, Veterinary Medicine & Small Animal Clinician. Veterinary Pub. Co.: Chicago. 1922. p.463.
7. 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.
8. Deol MS. The relationship between abnormalities of pigmentation and of the inner ear. Proc Roy Soc Lond A 1970;175:201-217.
9. Thrusfield P, Holt PE. 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.
10. Drury, WD. British Dogs, Their Points, Selection, and Show Preparation. L. U. Gill: London. 1903. pg. 377, 475.
11. FTG Hobday, J McCunn. Surgical diseases of the dog and cat: with chapters on anæsthetics and obstetrics. Bailliere, Tindall and Cox: London. 1906. p. 85
12. Busch TJ. Letter: Canine ear cropping. New Zeal Vet J 1983;31:205.
13. Smith BJ. Canine Anatomy. Blackwell: New Jersey. p.110.
14. Anatolian Shepherd dog: an ancient breed. Rangelands 1982;4:63-65.
15. Anatolian Shepherd dog breed standard. American Kennel Club: http://www.akc.org/breeds/anatolian_shepherd_dog/ Accessed January 2nd, 2008.
16. Strain GM. Aetilogy, prevalence and diagnosis of deafness in dogs and cats. Br Vet J 1996;152:17-36.
17. Rosser EJ. Causes of otitis externa. Vet Clin Small Anim 2004;34:459-468.
18. ASPCA. Cropping dogs’ ears: important action of the American Kennel Club. Our Animal Friends: An Illustrated Monthly Magazine 1895:23;1-3.
19. Ear cropping and tail docking of dogs. American Veterinary Medical Association: https://www.avma.org/KB/Policies/Pages/Ear-Cropping-and-Tail-Docking-of-Dogs.aspx Accessed February 12th, 2013.
20. CVMA Website Cosmetic Surgery: http://www.canadianveterinarians.net/documents/cosmetic-surgery Accessed February 12th, 2013.
21. AVA Website, Surgical alteration to the natural state of animals: http://www.ava.com.au/node/1085 Accessed February 12th, 2013.
22. The Council of Europe: http://conventions.coe.int/Treaty/en/Treaties/Html/125.htm Accessed February 12th, 2013.
23. The Kennel Club: http://www.thekennelclub.org.uk/item/979 Accessed February 12th, 2013.
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