CLINICO - DIAGNOSTIC AND THERAPEUTIC STUDIES ON OTITIS EXTERNA IN DOGS
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Date
2014-10
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SRI VENKATESWARA VETERINARY UNIVERSITY TIRUPATI - 517 502. (A.P.) INDIA
Abstract
ABSTRACT :
The present study was undertaken to study the etiology, make an attempt to identify the underlying factors, study the symptomatology and to assess the therapeutic efficacy of certain drugs in otitis externa in dogs. Upon screening of 610 dogs, during the study period of 7 months, the prevalence of otitis externa accounted for 6.88%. Of the affected dogs, 64.28% exhibited unilateral otitis externa and 35.71% showed bilateral otitis externa. Highest number of cases of otitis externa were observed in dogs of above 5 years age group (33.33%) with Labrador retreiever (22.80%) being the most affected breed. Of the total of 57 ears from 42 affected dogs , the primary etiological agents identified were Otodectes cyanotis, Sarcoptes scabei, Demodex canis, tick infestation, atopic dermatitis, food allergy, seborrhea, glandular disorders, canine distemper and Aspergillus. Predisposing factors identified included hair in the external ear canals, pendulous ears, ear polyps, use of cotton tipped swabs and high humidity. Secondary causative factors identified included Malassezia and bacteria. At least one of the secondary causative factors were identified in all the otitic ears.
The clinical signs observed in dogs with otitis externa included few or all of the symptoms like head shaking, ear discharge, ear scratching, pinnal erythema, malodour and pain on handling. Few affected dogs also showed reduced appetite, reduced general activity and skin lesions.
Examination of otic discharges by roll smear cytology of all the 57 otitic ears revealed Malassezia alone and bacteria alone in 22 (38.59%) and 14 (24.56%) ears respectively. The combination of bacteria and Malassezia were present in 21 ears (36.84%). Neutrophils were observed in the otic discharge of 50 ears (87.71%). The predominant bacteria found upon culture in healthy ears were Staphylococcus pseudintermedius which was isolated from 58.33% ears. Cultural examination revealed 34 bacterial isolates from 21 otitic ears with bacterial involvement (bacterial otitis externa – 10 and mixed otitis externa – 11), of which Staphylococcus species, Pseudomonas species and Proteus species accounted for 54.54 %, 18.18% and 12.12% of the otitic ears (Group I + Group II + Group III) respectively. Other bacteria isolated were Klebsiella species (6.06%), Streptococcus species and Micrococci (3.03%) each. Malassezia was isolated from 58.3% of healthy ears and 69.69% of the otitic ears (Group I + Group II + Group III) where as Aspergillus and Candida were obtained from 6.06% and 3.03% of the otitic ears respectively. Otitic dogs exhibited neutrophilia, eosinophilia, reduced haemoglobin and reduced total protein levels when compared to healthy animals. Video - otoscopic findings included purulent (4 ears) and ceruminous (3 ears) secretions that were not very conspicuous grossly, ulceration of external ear canal (3 ears) and excessive hair in the external ear canal (4 ears). Insipissated pus was observed in 1 ear out of the 4 purulent ears. Gentamicin and clotrimazole exhibited highest in- vitro sensitivity to whole culture samples from bacterial and fungal otitic ears respectively. Therapeutic trials were undertaken based on the etiology and dogs were divided into 3 groups. It was found that clotrimazole was 100% effective in treating Malassezial otitis externa (Group I dogs). Bacterial otitis externa (Group II dogs) had 100% recovery upon therapy with gentamicin, enrofloxacin and ciprofloxacin based on the results of antibiotic sensitivity tests of whole culture samples. In mixed otitis externa (Group III dogs), clotrimazole and ofloxacin were used and all the treated dogs recovered indicating 100% efficacy. The mean duration of time required for complete clinical recovery was 11.66 ± 1.60 days ( ranged from 7-21 days) in Malassezia otitis externa, while it was 17.50 ± 2.18 days (7-28 days) in bacterial otitis externa which might be due to the presence of Pseudomonas otitic infections which were relatively difficult to treat due to resistance. The time taken for complete clinical recovery was about 15.90 ± 2.32 days in mixed otitis externa which ranged from 7 – 28 days. It was observed that gram positive infection responded quickly than when combined with other organisms, particularly gram negative rods. Besides otitis externa, the associated conditions were also treated appropriately and during the monitoring period of three months no recurrence was seen.
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