Praca oryginalna Original paper
Inflammation of the external ear canal (otitis externa), which is a disease of the external auditory canal skin, has a multifactorial etiology. Acute disease is charac-terized by swelling, erythema, soreness (itching), and increased secretion from skin glands in the ear duct, which in clinical veterinary nomenclature is defined as erythema-ceruminous inflammation. In the course of chronic otitis externa lichenification appears in the skin of the ear canal; i.e. hyperkeratosis, hyperpigmen-tation and skin hyperplasia accompanied by a bacte-rial, fungal (yeast), or mixed infection. External otitis occurs in 8-20% of dogs; in addition 50% of chronic, recurrent inflammatory conditions end up with the damage of the tympanic membrane, thereby otitis media (1, 3, 5, 6, 13, 14, 26). The development of otitis externa is affected by many factors, hence the distinc-tion between primary, secondary, and recurrent otitis (11-13, 29). The primary cause of inflammation of the external auditory duct are parasites (itch mites, mange mites, fleas, ticks), foreign body acoustic duct irrita-tion, allergic diseases (atopic dermatitis, intolerance/ food allergy, hypersensitivity to drugs), and autoim-mune diseases (pemphigus, lupus erymatosus), which
cause disorders of epidermal keratinization, gland secre-tion and ear skin immune mechanisms. Not without significance are the factors predisposing to the deve-lopment of otitis externa, among which are the shape of the auricle, anatomic ear duct stenosis, its excessive hair growth, and the presence of primary lesions such as tumors. Secondary inflammations of the external auditory canal are ear inflammations occurring as amended by the primary and predisposing factors (4, 11, 13, 18, 23, 29). They are caused by perpetual factors such as bacteria and fungi (yeast) or drugs that in favorable circumstances worsen pathological changes. The combination of activities of primary, predisposing and secondary factors are recurrent or not amenable to treatment acute external ear inflammations, which are the greatest diagnostic and therapeutic problem for the practitioner.
The aim of the study was the assessment of the quantitative and qualitative cases of the inflammation of the external ear canal in dogs treated at the Derma-tological Consultation Room of Veterinary Clinics at the University of Life Sciences in Lublin (Poland) in the years 2007-2011.
Study of external ear canal inflammation in dogs
from the Lublin Region in the years 2007-2011
IWONA TASZKUN
Sub-department of Clinical Diagnostics and Veterinary Dermatology, Department and Clinic of Internal Medicine, Faculty of Veterinary Medicine, University of Life Sciences, Akademicka 13, 20-950 Lublin, Poland
Taszkun I.
Study of external ear canal inflammation in dogs from the Lublin Region in the years 2007-2011
Summary
The aim of the study was the assessment of the quantitative and qualitative cases of the inflammation of the external ear canal (otitis externa) in dogs treated at the Dermatological Consultation Room of Veterinary Clinics at the University of Life Sciences in Lublin in the years 2007-2011. The study group consisted of 240 dogs (135 females and 105 males), of various breeds, aged 8 weeks to 16 years. In 62.5% of dogs with otitis externa the diagnosis of atopic dermatitis (AD) was established, 4.58% of the dogs were diagnosed with otodectosis (Otodectes cynotis), 2.93% with contact dermatitis, 0.83% autoimmune disease, while in 5.83% anatomical changes were found in the auditory canal. Dogs with otitis externa up to 1-year-of-age accounted for 24.58% of the research group, aged 1-3 years 48.33%, and aged over 3 years 27.09%. Unilateral inflammation of the external ear canal was diagnosed in 31.67% patients and bilateral in 68.33%. In 65.42% of dogs with otitis externa a chronic and relapsing nature of the disease was found. Dogs in which in addition to otitis externa dermatological symptoms located in other areas of the body were found accounted for 67.08% of the research group.
Keywords: canine otitis externa, external ear diseases, canine atopic dermatitis, epidemiology of canine otitis externa
Material and methods
The study group consisted of 240 dogs (135 females and 105 males, different breeds, aged 8 weeks to 16 years) with inflammation of the external ear canal (otitis externa). The history of the disease was taken from animal owners and detailed clinical studies of dogs were performed to identify the co-occurrence of other dermatological symptoms. Auricles and external auditory canals were examined using a veterinary otoscope with a xenon-halogen illuminating head (Heine Optotechnik, Germany). The otoscopic me-thod allowed the evaluation of anatomical changes in the ear canal and the examination of the tympanic membrane to exclude otitis media. In each dog with otitis externa, a microscopic examination of ear wax was performed with the use of chlorolactofenol to confirm the presence of parasites (Otodectes cynotis, Demodex canis), as well as a cytological examination of the material taken from the horizontal part of the acoustic duct. Cytological prepara-tions were stained by Diff-Quick method using Hemacolor kit for quick staining of blood smears (Merck Chemicals, Germany), which allowed the identification of keratino-cytes, endothelial cells and microbial agents, such as Gram--positive bacteria, G-negative cocci and bacilli, and yeasts of the genus Malassezia spp. The diagnosis of atopic derma-titis (AD) was based on the medical history data, clinical trial results and positive results of intradermal tests using a set of allergens Artuvetrin Test (ART Biologicals Europe BV, The Netherlands) intended for dogs (8, 24, 31). The diagnosis of autoimmune diseases was based on the history,
clinical findings, and cytological and histopathological exa-mination of skin biopsies stained with HE (29).
Results and discussion
The studies conducted in 2007-2011 revealed that the list of breeds of dogs with otitis externa is rich (Tab. 1). Most frequently otitis externa was found in French and English bulldogs (18.75%), terriers, (mainly American Staffordshire terriers) (17.50%), boxers (13.75%), German Shepherds (13.3%), dachshunds (6.67%) and mixed breed (10.84%) (Tab. 1). These breeds accounted for a total of nearly 70% of the research group of dogs with otitis externa. Least often (less than 4%), otitis externa was found in schnauzer dogs, Dogue de Bordeaux and Dalmatians. A similarly wide range of breeds of dogs with otitis externa is present in the studies of other authors (10, 21, 30).
Among the primary factors of otitis externa in dogs are most commonly reported diseases connected with hypersensitivity: atopic dermatitis (AD) and intolerance/ food allergy (I/FA). These diseases are the cause of otitis externa in 40-90% of dogs (9, 21, 25). In con-trast, autoimmune diseases are diagnosed in 2% of otitis externa, and parasites Otodectes cynotis in 5-26% of dogs with otitis externa (13, 21, 25). According to many authors (8, 13, 25), otitis externa in dogs may be the only clinical sign of skin hypersensitivity diseases (AD and I/FA) in 5-30% of cases, whereas in 55-90% Tab. 1. Dogs with otitis externa including the breed and diagnosis of primary factors
d e e r B oNituitmsebxetreornfadoagnsdwthtiehri d e e r b e h t f o e g a t n e c r e p h ti w s g o D s i s o t c e d o t o dearmtopaiitcits dceromntaacittits audtoisei-masmeusne chaannagteosmiincatlhe l a n a c r a e l a t o T 240(100%) 11(4.58%) 150(62.5%) 7(2.93%) 2(0.83%) 14(5.83%) d e e r b d e x i M 26(10.84%) 4(1.67%) 13(5.42%) 0 0 0 g o d ll u b h s il g n E d n a h c n e r F 45(18.75%) 4(1.67%) 30(12.5%) 4(1.67%) 0 3(1.25%) n a c ir e m A y l n i a m ( r e ir r e T )r e ir r e t e ri h s d r o ff a t S 42(17.50%) 0 37(15.41%) 0 0 0 r e x o B 33(13.75%) 0 30(12.5%) 3(1.25%) 0 0 d r e h p e h s n a m r e G 32(13.30%) 0 10(4.17%) 0 2(0.83%) 5(2.08%) d n u h s h c a D 16(6.67%) 0 2(0.83%) 0 0 3(1.25%) r e li e w tt o R 10(4.17%) 0 6(2.50%) 0 0 r e tt e S 8(3.33%) 0 5(2.08%) 0 0 2(0.83%) r o d a r b a L 8(3.33%) 2(0.83%) 6(2.50%) 0 0 0 r e v e ir t e r n e d l o G 6(2.50%) 0 6(2.50%) 0 0 0 i e p r a h S 3(1.25%) 1(0.42%) 1(0.42%) 0 0 1(0.42%) l e i n a p S 3(1.25%) 0 1(0.42%) 0 0 0 r e z u a n h c S 2(0.85%) 0 1(0.42%) 0 0 0 x u a e d r o B e d e u g o D 2(0.84%) 0 1(0.42%) 0 0 0 n a it a m l a D 2(0.84%) 0 1(0.42%) 0 0 0 r e h t O 2(0.84%) 0 0 0 0
cases of these diseases it is one of many clinical symp-toms.
In this study 150 (i.e. 62.5% of dogs) with otitis externa were diagnosed with atopic dermatitis (AD). The dogs were mainly terriers (American Staffordshire Terrier), French and English bulldog, boxer, German Shepherd, Rottweiler, golden retriever, Labrador, and mixed breed (Tab. 1). In 11 dogs (4.58%), the primary cause of otitis externa was ear parasites (Otodectes cynotis), in 7 (2.93%) contact dermatitis, in 2 (0.83%), autoimmune diseases, while in 12 (5.0%) anatomical changes in the ear duct. The primary cause of otitis externa was not determined in 56 dogs, i.e. in 23.33% of the research group. In 150 dogs with otitis externa, diagnosed with atopic dermatitis, lesions were located in other areas of the body (Fig. 1). These mainly included the skin of the pectoral and pelvic limb interdigital spaces, underarms, chin, and mouth and eye area. In 16 dogs from the studied group (10.67%), otitis externa was the only clinical sign of AD.
In the present study, the dogs under 1-year-of-age accounted for 24.58% of patients with otitis externa, aged 1 to 3 48.33%, adults aged 3-7 years 15.42%, while aged over 7 years 11.67% (Tab. 2). Available literature data show that 10-16% of cases of canine otitis externa refer to the dogs up of to1-year-old, 44-60% are dogs aged from 1 to 5 years, 24-44% are dogs over 5-years-old (21, 30), of which even in 94% of cases include inflammation of both ears (21).
In this study for 65.42% of dogs otitis externa was of a chronic, relapsing nature, with over 68% of the animals which did not exceed the age of 3 years (Tab. 2). The group with acute otitis externa, (34.58% of the research group) was dominated by animals under the age of 1 year, which accounted for 67.47% of the group. The results are similar to those obtained by other authors (21), who reported that a chronic and recurrent nature of the disease is observed in approxi-mately 59% dogs with otitis externa.
Bilateral inflammation of the external auditory canal was found in 68.33% of the group of animals, and uni-lateral in 31.67% (Tab. 3). Clinical features of acute inflammation were found in 34.58%
of the research group of dogs, and clinical symptoms of chronic, recur-rent inflammation in 65.42% of dogs (Tab. 3), whereas bilateral chronic, recurrent otitis externa was found in 44.58% of dogs. Dogs with otitis externa in addition to dermatological lesions located in other areas of the body accounted for 67.08% of the research group. The group was strongly dominated by animals with bilateral inflammation of the external canal (60.41%). However, the dogs, which had no other dermatological lesions apart from otitis externa,
constituted 32.92% of the research group (Tab. 3). In this group, 60 dogs (25%) had only one ear infection, the cause of which was the foreign body, proliferative skin changes in the auditory duct narrowing the duct, and drug-induced contact dermatitis.
Among the secondary factors that cause otitis externa are mentioned mainly Gram-positive bacteria (Staphy-loccccus spp., Streptococcus spp.), G-negative (Pseu-domonas spp.) and fungi (Malassezia spp., Candida spp.). Assessment of etiologic factors isolated from the ear wax of dogs with otitis externa showed that the most frequently found were mixed (bacterial-yeast) Tab. 2. The number and percentage of dogs with otitis externa in different ages number (%)
e g A ) s r a e y ( h ti w s g o D a n r e t x e s it it o r e h t e g o tl a aceuxtteeronaitits chroonitiitcs,erxetceurnrraent 1 o t p U 159(24.58) 56(67.47) 13(1.91) 3 -1 116(48.33) 11(13.25) 105(66.88) 7 -3 137(15.42) 12(14.46) 125(15.92) 7 r e v O 128(11.67) 4(4.82) 124(15.29) l a t o T 240(100).0 83(34.58) 157(65.42)
Tab. 3. Clinical evaluation of the external auditory canal inflammation in canine patients number (%) d e i d u t s a n r e t x e s it it o f o e r u t a e F To(t%al)ninumthbeer p u o r g h ti w s g o D r a e l a r e t a li n u n o it a m m a lf n i ibnlilfaatmermalaeitaorn s g o d f o r e b m u N 240(100) 76(31.67) 164(68.33) h ti w s g o D a n r e t x e s it it o e t u c a 183(34.58) 26(10.83) 157(23.75) a n r e t x e s it it o c i n o r h c 157(65.42) 50(20.84) 107(44.58) s n o i s e l l a c i g o l o t a m r e d r a e h ti w g n ir r u c c o -o c n o it a m m a lf n i 161(67.08) 16(6.67) 145(60.41) t u o h ti w s g o D dcoe-romcactuorloirnggicawltilheseioanrs n o it a m m a lf n i 79(32.92) 60(25.00) 19(7.92)
Fig. 1. Location of skin lesions in dogs with otitis externa diagnosed with AD
Explanations: p.m.k.p. thoracic limb interdigital spaces; p.m.k.m. hind leg interdigital spaces; other the neck, base of the tail, anus, lumbosacral areas
inflammations of the external auditory canal (53.33%); exclusively bacterial (23.75%) or yeast (18.75%) infections were much less frequent (Tab. 4). The cyto-logical study of 4.17% of the dogs showed no micro-bial etiological agent (aseptic otitis externa); the dogs were under 1-year-of-age in which the disease course was acute. Mixed infections were most common in dogs with bilateral inflammation of the external audi-tory canal, regardless of whether the disease was acute or chronic (Tab. 4). Exclusively bacterial etiologic fac-tors just as exclusively fungal ones were identified most frequently in dogs suffering from chronic otitis externa. In the group of young dogs (i.e. under 1-year--of-age), as in other age groups, most infections were mixed (bacterial-yeast), but it was the only age group in which a cause of otitis externa was identified as Otodectes cynotis and aseptic inflammation was dia-gnosed (Tab. 5). Males aged 1-3 years were the largest age group of animals in which the etiological agent of otitis externa and mixed infections were identified as exclusively bacterial. Bacterial and fungal infections in this age group occurred in nearly 28% of dogs with otitis externa, whereas exclusively bacterial infections in 11.67% (Tab. 5). In contrast, in dogs aged 3-7 years the bacterial agent was identified as often as a mixed one (bacterial and yeast). In dogs over 7-years-of-age mixed infections of the ears prevailed.
As reported by many authors (11, 16, 18), micro-biological factors may be isolated from the auditory canal of healthy dogs, but their participation in the
pathogenesis of otitis externa is un-deniable (2, 7, 9, 15, 17, 19, 20, 23, 27, 28). The findings indicate that most frequently (53.33%) the cases of otitis externa in dogs were diagnosed with a mixed bacterial and fungal in-fection, only rarely (23.75%) solely bacterial or solely fungal (18.75%). According to other authors (21, 22), the bacterial agent is isolated in 21.28% of cases of otitis externa in dogs, and fungal in 36.18%, with the dominating fungal factor in the dogs under the age of five (Malassezia spp., Candida spp.), whereas in older dogs both the fungal and bacterial factor are equally frequently isolated.
In conclusion, the obtained results indicate that the majority of otitis externa cases in dogs are bilateral, chronic and recurrent. They are caused by primary factors the diagnosis of which and elimination is a big challenge for the veterinary surgeon.
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Tab. 5. Etiologic factors identified in dogs with otitis externa in different age groups number (%)
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Corresponding author: Dr. Iwona Taszkun, Department and Clinic of Internal Medicine, Faculty of Veterinary Medicine, University of Life Sciences, G³êboka 30, 20-612 Lublin; e-mail: iwona.taszkun@up.lublin.pl
