Introduction
Otitis externa is inflammation of the external ear canal. It occurs predominantly in summer, with a prevalence of 4 per 1000 population.Reference Flint, Haughey, Lund, Niparko and Cummings 1 It is caused by either infection or dermatitis. Bacterial infections are the most common cause of otitis externa in subtropical areas, followed by fungal infections, which are responsible for 10–20 per cent of otitis externa cases.Reference Flint, Haughey, Lund, Niparko and Cummings 1 , Reference Kurnatowski and Filipiak 2 Otitis externa is also known as ‘swimmer's ear’ as it is more prevalent among swimmers and can appear after prolonged exposure to water.Reference Lee and Lee 3 – Reference Kaushik, Malik and Saeed 5
Otomycosis, or fungal otitis externa, may occur as an acute, subacute or chronic infection with clinical signs such as inflammation with exudate. Acute infection presents with earache accompanied by white exudate. Subacute infection is characterised by dry dermatitis, with itching and no exudate. In chronic infection, there is itching occasionally accompanied by scaling, with little exudate and no odour. Clinical symptoms normally start with itching and reduced hearing, and continue with erythema and inflammation of the external ear. As a result, densely impacted wax may form, comprising fungal mycelia and epithelial cells. This wax can partially close the external canal and may lead to hearing loss or even deafness. Cases of otomycosis with additional bacterial infection may develop a foul-smelling exudate, severe pain, inflammation and erythema. As such clinical symptoms are not specific to otomycosis, the definitive diagnosis should be based on direct histological examination and microbial culture.Reference Yamashita, Hashimoto, Ezaki, Iwami, Komori and Kohsaka 6 , Reference Fasunla, Ibebwe and Onakoya 7
Otomycosis is widespread, occurring predominantly in tropical and subtropical regions. The most common risk factors for the infection are: warm and damp weather; bacterial external otitis; swimming; close or continuous contact with water; eczema; seborrhoeic dermatitis of the external ear; external ear injury due to a foreign body; wearing headphones and hats; anatomical disorders; diabetes mellitus; and immune incompetency.Reference Lee and Lee 3 , Reference Jadhav, Pal and Mishra 8 Saprophytic fungi, candida species and dermatophytes are the main aetiological agents.Reference Fasunla, Ibebwe and Onakoya 7 – Reference Nwabuisi and Ologe 13
Otomycosis should be differentiated from seborrhoeic, streptococcal and contact dermatitis, as well as from allergic infections of the middle ear.Reference Kurnatowski and Filipiak 2 , Reference Loh, Tan, Kumarasinghe, Leong and Yeoh 14 – Reference Mishra, Mehta and Pal 16
This study was performed to evaluate the prevalence of otomycosis and its aetiological agents in Khouzestan province in south-west Iran, previously a war zone for many years, with a climate which is usually very hot and humid.
Patients and methods
We investigated 881 patients from different regions of Khouzestan province who were suspected of having otomycosis. After being examined by an otolaryngologist, a questionnaire was completed and samples were obtained for laboratory examination.
Mycological analysis was carried out on debris, scrapings or exudate samples obtained from the external auditory canals of patients clinically suspected of otomycosis. Samples were collected using a sterile cotton swab, placed in sterile normal saline and transferred to the laboratory.
In order to detect fungal elements, specimens were examined under direct microscopy using KOH (10 per cent), Gram staining and periodic acid Schiff staining. Samples were also inoculated onto Sabouraud's dextrose agar with and without antibiotics and incubated at 25 and 37°C, variously, for a minimum period of 4 weeks, and were evaluated every 2 days for the presence of fungi. The diagnosis of otomycosis was made based on microscopic identification of the characteristic appearance of fungal ‘mats’ and fruiting bodies.
Results
Upon laboratory examination, 293 patients were diagnosed with otomycosis: 162 (55.3 per cent) women and 131 (44.7 per cent) men. The highest prevalence was seen in the 20–39 year age group. There was a male preponderance amongst patients younger than 20 years, but in other age groups the disease was more prevalent amongst women (Table I).
Table I Otomycosis cases by sex and age
Data represent patient numbers. Y = years
When patients’ occupations were analysed, we found a preponderance of homemakers, animal husbanders, private sector employees, farmers and students (Table II).
Table II Otomycosis cases by occupation
Data represent patient numbers.
The aetiological agents were Aspergillus niger (67.2 per cent), A flavus (13 per cent), Candida albicans (11.6 per cent), A fumigatus (6.2 per cent) and penicillium species (2 per cent) (Table III).
Table III Otomycosis cases by fungal aetiology and sex
Data represent patient (Pt) numbers. A = Aspergillus; C = Candida; Sp = species
The seasonal distribution was: summer, 44.7 per cent; autumn, 28.7 per cent; winter, 14.7 per cent; and spring, 11.9 per cent.
Discussion
Otomycosis is one of the most common infections especially in humid tropical and subtropical climates.Reference Munguia and Daniel 17 The differentiation of otomycosis from other types of otitis externa is important to enable appropriate treatment.Reference Martin, Kerschner and Flanary 18 In this study, otomycosis was diagnosed in 33.25 per cent of patients suspected of otitis externa.
Similar studies have reported different rates of infection.Reference Kurnatowski and Filipiak 2 , Reference Nwabuisi and Ologe 13 , Reference Mishra, Mehta and Pal 16 , Reference Pradhan, Tuladhar and Amatya 19 – Reference Fasunla, Ibekwe and Onakoya 21 The high prevalence found in our study may be associated with the humid and subtropical climate, dusty conditions, high prevalence of immune incompetency, and low hygiene standards common in the study region. Although infection occurred in all age groups, the highest prevalence was observed in 20–39 year olds; this is similar to most other studies.Reference Fasunla, Ibekwe and Onakoya 21 , Reference Ologe and Nwabuisi 22 There is no clear explanation for this finding, but the greater range of activities undertaken in this age group may lead to greater exposure to environmental fungal agents.
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• This study assessed otomycosis in Khouzestan province, south-west Iran
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• This area was previously a war zone, and is very hot and humid
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• Aspergillus niger was the commonest fungal aetiology
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• Candida albicans was less common, but more prevalent in 20–39 year olds
Our study identified more cases of otomycosis amongst women (55.3 per cent) than men (44.7 per cent), consistent with other studies.Reference Ologe and Nwabuisi 22 , Reference Brobby 23 This may be because women are more conscious of their health and thus use cotton swabs to clean their ears more frequently, resulting in a higher moisture level in the external auditory canal, which is a risk factor for otomycosis.Reference Donamayor Hernandez 11 , Reference Yehia, Al-Habib and Shehab 20 On the other hand, swabs can protect the ear from environmental contaminations and reduce the level of exposure to environmental fungal agents.Reference Burgos, Menaches, Gras and Talavera 12 This aspect of otomycosis aetiology needs further investigation.
Aspergillus niger was the most common fungal aetiological agent in this study, consistent with most previous studies.Reference Fasunla, Ibebwe and Onakoya 7 , Reference Fasunla, Ibekwe and Onakoya 21 , Reference Kazemi and Ghiaei 24 – Reference Sefidgar, Kiakojouri, Mirzaei and Sharifi 26 This finding might be explained by the fact that aspergillus is present in polluted air, although no clear explanation yet exists.
This study found no significant relationship between occupation and fungal infection, probably because saprophytic fungi are distributed in all environments.
Clinicians should be aware that 20–39 year olds are at a higher risk of otomycosis.Reference Burgos, Menaches, Gras and Talavera 12 , Reference Ologe and Nwabuisi 22 , Reference Kazemi and Ghiaei 24
The limitations of this study include a possible selection bias given the referral pattern of our practice. In addition, the high heat and humidity in our study region may limit the applicability of our findings in regions with a more temperate climate.
Nevertheless, to our knowledge this series represents one of the largest otomycosis surveys reported worldwide.
Conclusion
Fungal otomycosis is still one of the most important types of external ear infections. In the region in which this study was conducted in south-west Iran, Aspergillus niger was the predominant fungal aetiological agent. Although candidal otomycosis had a lower rate of incidence, clinicians should be aware of this aetiology especially among 20–39 year olds.
Acknowledgement
This study was supported by the Research Deputy of Ahvaz Jundishapour University of Medical Science (registration number 85105); we are very grateful for their support and permission to publish the study data.
