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Clinico--diagnostic and therapeutic studies on Malassezia otitis externa--study of 12 ears.


Otitis externa is a common multifactorial disease accounting upto 10-20% of canine veterinary consultations (Scott et al., 2001). Yeast (Malassezia pachydermatis) is the most common organism isolated from external ear canals (Hallu et al., 1996). The present study presents symptomatology, antifungal sensitivity and therapeutic efficacy in dogs with Malassezia otitis externa.

Materials and Methods

Eight dogs (12 ears) of various breeds presented with symptoms of otitis externa and elevated populations of yeasts in otic discharges (>4 Malassezia organisms/ field) as viewed under an oil immersion lens were included in study (Cole et al., 1998). The dogs were thoroughly examined and scores were given for each observations on a severity scale of 0-3 (0-absent, 1-slight, 2-moderate and 3- severe) as suggested by Grandemange et al. (2013). The otic swabs were transferred into Sabouraud's dextrose broth containing Chloramphenicol and incubated at 37[degrees]C for 24-48 hours. The broth culture was streaked onto Sabouraud's dextrose agar with Chloramphenicol and incubated at 30[degrees]C for 1-7 days. The plates were daily examined for fungal growth. The drug sensitivity was performed on mixed culture isolates using disc diffusion method.

Certain haemato-biochemical parameters were performed in order to detect any underlying causes. In four dogs, video--otoscopy was undertaken as per standard technique after anesthetising the dog. Before undertaking therapy, ear cleaning was performed after instillation of ceruminolytics. Therapy was instituted with topical Clotrimazole ear drops at a dose rate of 3 drops b.i.d in small breeds and 5 drops twice daily in large breeds (Kiss et al., 1997b). Dogs were monitored clinically and cytologically at weekly intervals. Even after recovery, ear drops were continued for another week and Ketoconazole shampoo was advised to be continued for further 2 months.

Results and Discussion

Brown color ear discharge was observed in many Malassezia otitic ears as also reported by Chickering (1988). Other common findings included ear scratching and mal odour (Table 1). Ear scratching might be due to peroxides produced by Malassezia which promote pruritis (Kiss et al., 1997a). The aural discharge may become purulent, moist and develop foul odour, when complicated by fungal infections (Muller et al., 1989). Neutrophils were observed in otic discharge of 10 ears. Range of Malassezial organisms per oil immersion field were 4-10 (6 ears), 11-20 (3 ears), 21-30 (2 ears) and >30 (1 ear) (Fig. 1). In one otitic ear, Candida (Fig. 2) was observed along with Malassezia on examination of tape impression smear (100 X). On periodical monitoring, it was noticed that by 7, 14 and 21 days the yeast count became normal in 5, 4 and 3 ears respectively. Identification of Malassezia pachydermatis was based on macroscopic appearance of white, later yellow or light brown coloured colonies with convex surfaces that are smooth and dry (Fig. 3) as stated by David et al. (2003).












Haematobiochemical values were within normal range except for eosinophilia Video otoscopic studies (Fig. 4) revealed ceruminous secretions (Fig. 5) and excessive hair in the external ear canal of that were not grossly clearly visible (Fig. 6) in 3 and 4 ears respectively as also suggested by Rosser (2004).

An efficacy of 100% was observed on treatment with Clotrimazole ear drops. However, in vitro antifungal sensitivity of whole cultures to Clotrimazole was 91.30% (Fig. 7). This difference could be explained by the fact that drug concentrations were much higher in ear (100-1000 times) than on sensitivity discs (Cole, 2013).

The lower limit of duration of therapy was about 7 days in 6 otitic ears (relatively less number of Malassezia organisms/OIF) and 14 days in 3 otitic ears (moderate number of Malassezial organisms/OIF). It took 21 days in three ears in which primary factors like Aspergillus (Miller et al., 2013) (Fig. 8) and glandular abnormalities (Labrador retriever-2 ears) (Fig. 10) were detected. Aspergillus (Fig. 9) was isolated from 1 otitic ear. Bass (2004) stated that Labrador retrievers have increased apocrine and ceruminous glands which lead to excess glandular secretions (Fig. 10). However, no conspicuous ear discharge was observed after therapy indicating complete recovery (Fig. 11).

It took 11.66 [+ or -] 1.60 days for clinical recovery and 12.83 [+ or -] 1.68 days for cytological recovery. In the present study, primary causes were determined in 3 otitic ears. Saridomichelakis et al. (2007) also reported that no primary cause could be detected in 30.56% of ears in their study.


The present study concluded that, dogs with Malassezia otitis externa showed symptoms of brown color ear discharge, ear scratching and malodour more commonly. Haematology revealed eosinophilia and on Video otoscopy revealed, excessive hair in external ear canal (not grossly clearly visible) and ceruminous secretions. Highest in vitro sensitivity and 100% clinical recovery (7-21 days) was noticed with topical Clotrimazole instillation. Recovery period was prolonged with underlying conditions of Aspergillosis and glandular disorders (Labrador retriever).


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C. Bharath Kumar Reddy [1], K. Nalini Kumari [2], N. Syaama Sundar [3] and N. Vinod Kumar [4]

Department of Veterinary Medicine

College of Veterinary Science

Sri Venkateswara Veterinary University (SVVU)

Tirupati--517502 (Andhra Pradesh)

[1.] Teaching Assistant and Corresponding author. E-mail:

[2.] Professor and Head

[3.] Professor and Head, Department of Veterinary Medicine, College of Veterinary Sciences, Proddatur.

[4.] Assistant Professor, Department of Veterinary Microbiology
Table 1: Symptomatology of Malassezia otitic ears (12 ears)

S.No   Symptoms           Frequency      +1         +2         +3

1.     Mal odour          7(58.33)    4(33.33)   2(16.66)   1(8.33)
2.     Ear scratching     10(83.33)   5(41.66)    3(25)     2(16.66)
3.     Pain on handling   2(16.66)       --      2(16.66)      -
5.     Ear discharge      11(91.66)   6(50.00)   3(25.00)   2(16.66)
6.     Color
       a) Brown           7(58.33)    4(33.33)   1(8.33)    2(16.66)
       b) Yellow          2(16.66)    2(16.66)      --         --
       c) Black           2(16.66)       --      2(16.66)      --
7.     Pinnal erythema    7(58.33)    5(41.66)   2(16.66)      --
8.     Head shaking       11(91.66)   6(50.00)   3(25.00)   2(16.66)
9.     Reduced appetite   3(25.00)    3(25.00)      --         --
10.    Skin lesions       2(16.66)    2(16.66)      --         --
11.    Reduced general    3(25.00)    3(25.00)      --         --
12.    Ear scaling/       4 (33.33)      --         --         --
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Title Annotation:Clinical Article
Author:Reddy, C. Bharath Kumar; Kumari, K. Nalini; Sundar, N. Syaama; Kumar, N. Vinod
Publication:Intas Polivet
Article Type:Report
Date:Jul 1, 2015
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