512119 2013
JFM0010.1177/1098612X13512119Journal of Feline Medicine and SurgeryPerego et al
Original Article Journal of Feline Medicine and Surgery 0(0) 1–8 © ISFM and AAFP 2013 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/1098612X13512119 jfms.com
Prevalence of otitis externa in stray cats in northern Italy
Roberta Perego, Daniela Proverbio, Giada Bagnagatti De Giorgi, Alessandra Della Pepa and Eva Spada
Abstract
Feline otitis externa is a dermatological disorder that has not been evaluated much in stray cats. One hundred and eighty-seven stray cats were randomly selected during a trap–neuter–release programme to investigate the prevalence of otitis externa in stray cat colonies in northern Italy. Swabs for cytological examination were obtained from the external ear canal of each cat. A direct otoscopic assessment of the external ear canal was made in 86/187 cats. Cytological evidence of otitis externa was present in 55.1% of cats. The influence on otitis of age, gender, habitat and season of sampling were tested, but no risk factors were found. Otodectes cynotis (as a sole agent or in combination) was the primary cause of otitis in 53.3% of cats. Cocci and rods, either alone or in combination with other agents, were perpetuating factors in 71.8% and 29.1% of cats, respectively. Pregnancy status was a risk factor for otitis caused by coccal infections. Malassezia species, alone or in combination, was the perpetuating factor in 50.5% of cats with otitis. Urban habitat and winter season were risk factors for otitis associated with Malassezia species. Demodex cati was identified as an incidental finding in two cats. There was good agreement between otoscopy and cytology with regard to the diagnosis of otitis externa. The results of this study show a high prevalence of otitis externa in stray colony cats and provide information on causal factors for feline otitis externa. Accepted: 14 October 2013
Introduction Otitis externa is a multifactorial and aetiologically complex disorder of the ear canal in domestic animals, including the cat.1 Diagnosis is usually by means of direct otoscopic examination and cytology of otic exudates.2,3 There is a paucity of published data on the prevalence or incidence of feline otitis. A few older studies report prevalence in pet cats to be between 2% and 10%.4–6 More recently, a study of pet cats in the UK7 reported a prevalence of 19%, although no information about the diagnostic methods used or the size of the study population was reported. A Romanian study8 reported a prevalence of 2% in a population of 4572 domestic cats. However, neither study considered the aetiology and/or the microorganisms involved in the development of otitis externa. Not much information is available about otitis externa in stray cats. Although it is considered the principal primary cause of feline otitis externa,1 there are surprisingly little data on the prevalence of Otodectes cynotis in stray cats and the prevalence reported varies between 0.6% and 37.0%.9–12 To our knowledge there are no studies about the prevalence of Malassezia species in the external ear canal of
either healthy stray cats or those with otitis, while the bacteria most commonly isolated by culture from the ears of feral cats are coagulase-negative staphylococci (with Staphylococcus felis/Staphylococcus simulans the most common) and Bacillus species.13 However, in that study, conducted in Grenada, neither ear cytology nor otoscopic evaluation were performed, and therefore the presence or absence of otitis externa could not be confirmed. Evaluation of the health status of free-roaming stray cats is important for the improvement of animal welfare14 and to obtain information about regional pathogens and diseases, regardless of their infectivity. Data on diseases in stray cat populations are needed to define their role in the transmission of some pathogenic agents Department of Veterinary Sciences for Health, Animal Production and Food Safety, University of Milan, Italy Corresponding author: Roberta Perego DVM, PhD, Department of Veterinary Sciences for Health, Animal Production and Food Safety, University of Milan, via Celoria, 10, 20133 Milan, Italy Email: [email protected]
Downloaded from jfm.sagepub.com at University of Birmingham on March 22, 2015
Journal of Feline Medicine and Surgery 0(0)
2 such as O cynotis, to other susceptible animals and domestic cats that have access to the outdoors.11,15–17 The aim of this study was to assess the prevalence of otitis externa in a population of stray cats of northern Italy and to evaluate the concordance of cytology and direct otoscopic examination as means of diagnosis of otitis externa. The study also characterises risk factors for feline otitis externa, including gender, age, habitat, season of sampling and microorganism identified at the ear cytology.
Material and methods Sampling and data collection Cases included 187 short haired stray cats from colonies in the Lombardy region of northern Italy, regardless of the presence/absence of signs of otitis externa. The cats were trapped by volunteers between 2008 and 2010, during a trap–neuter–return (TNR) programme approved by the city council, as previously described.15,16 Swabs were obtained from the external ear canal of each cat for cytological examination. The gender and habitat of each cat were recorded together with the data obtained from cytological ear evaluation. Age was estimated by dentition and animals were classified as young (⩽6 months of age) or adult (⩾6 months of age). To evaluate seasonal trends the samples were categorised according to the sampling period: spring samples (from March to May), summer samples (from June to August), autumn samples (from September to November) and winter samples (from December to February). For technical reasons, direct otoscopic assessment of the external ear canal was made in 86/187 cats, all from urban colonies. Evaluation included alterations of quantity and/or quality of ear wax (characterised grossly as normal or abundant and clear, yellow, brown or typically black with the presence of mites) and ear canal alterations (erythema, stenosis, ulceration). Cytological evaluation Samples for cytological evaluation were obtained with two sterile cotton swabs (one per ear) inserted into the lumen of the ear canal and swabbed against the surface of the vertical canal. Each cotton swab was rolled onto two clean microscope slides, evenly distributing a thin layer of material. One slide per ear was unstained, suspended with mineral oil and mounted with a cover slip, and one slide per ear was heat-fixed, stained with modified Wright’s rapid stain (Quick Panoptic Kit; Pokler Italia), suspended with mineral oil and mounted with a cover slip.2 Both slides were examined immediately. The unstained slide was scanned at low power (100×) for the presence of O cynotis, and the total number of mites was recorded. The detection of a single mite in at least one ear indicated the presence of infection in the cat.18
The stained slide was evaluated first at low power (100×) (to identify the areas of interest) and then under high power (400×) to evaluate the presence and number of microorganisms morphologically identifiable as Malassezia species and/or bacteria. As both bacteria and Malassezia species are common inhabitants of the normal feline external ear canal, a cytological score for the presence/absence of otitis in each cat was developed based on the average of the different values previously reported in the literature (Table 1).19–21 Briefly, each parameter evaluated microscopically (presence of cocci, rods and Malassezia species) was given a score from 0 (normal) to 2 (pathological) based on the mean number of detected microorganisms seen in 10 high-power dry fields (400×). Higher-power oil immersion fields (1000×) were chosen by scanning at low power until staining was visualised; by focusing on areas of staining, different kinds of bacteria (cocci or rods) were identified. A value score equal to 1 (or grey zone) is a cytological transitional zone proposed by previous authors20 in which other clinical criteria, including signs of otitis, are taken into account to make a diagnosis of otitis. Animals with a score in the grey zone were classified as normal because the number of microrganisms was lower than the clinically significant limit20 and clinical examination of the ears was not always possible. Cats were considered to be suffering from otitis externa when at least one of the evaluated parameters (cocci, rods and Malassezia species) had a cytological score of 2 in at least one ear. Statistical analysis Overall prevalence was defined as the percentage of cats diagnosed with otitis based on cytological examination of ear swabs. Prevalence data were regrouped according to age (young/adult), gender (male/female), pregnancy status (yes/no), habitat (urban/rural), season of sampling (spring/summer/autumn/winter), type of otitis based on microorganisms detected using ear cytology (Malassezia species/cocci/rods/Otodectes species). Univariate analysis of the categorical data was
Table 1 Cytological score based on the mean number of microorganisms identified in 10 different high-power dry fields (400×) Score 0 (Normal) Malassezia ⩽2 species (n°) Cocci (n°) ⩽4 Rods (n°) 0 *Ginel et al20
Downloaded from jfm.sagepub.com at University of Birmingham on March 22, 2015
1 (Grey zone)*
2 (Pathological)
>2 to 4 to
JFM0010.1177/1098612X13512119Journal of Feline Medicine and SurgeryPerego et al
Original Article Journal of Feline Medicine and Surgery 0(0) 1–8 © ISFM and AAFP 2013 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/1098612X13512119 jfms.com
Prevalence of otitis externa in stray cats in northern Italy
Roberta Perego, Daniela Proverbio, Giada Bagnagatti De Giorgi, Alessandra Della Pepa and Eva Spada
Abstract
Feline otitis externa is a dermatological disorder that has not been evaluated much in stray cats. One hundred and eighty-seven stray cats were randomly selected during a trap–neuter–release programme to investigate the prevalence of otitis externa in stray cat colonies in northern Italy. Swabs for cytological examination were obtained from the external ear canal of each cat. A direct otoscopic assessment of the external ear canal was made in 86/187 cats. Cytological evidence of otitis externa was present in 55.1% of cats. The influence on otitis of age, gender, habitat and season of sampling were tested, but no risk factors were found. Otodectes cynotis (as a sole agent or in combination) was the primary cause of otitis in 53.3% of cats. Cocci and rods, either alone or in combination with other agents, were perpetuating factors in 71.8% and 29.1% of cats, respectively. Pregnancy status was a risk factor for otitis caused by coccal infections. Malassezia species, alone or in combination, was the perpetuating factor in 50.5% of cats with otitis. Urban habitat and winter season were risk factors for otitis associated with Malassezia species. Demodex cati was identified as an incidental finding in two cats. There was good agreement between otoscopy and cytology with regard to the diagnosis of otitis externa. The results of this study show a high prevalence of otitis externa in stray colony cats and provide information on causal factors for feline otitis externa. Accepted: 14 October 2013
Introduction Otitis externa is a multifactorial and aetiologically complex disorder of the ear canal in domestic animals, including the cat.1 Diagnosis is usually by means of direct otoscopic examination and cytology of otic exudates.2,3 There is a paucity of published data on the prevalence or incidence of feline otitis. A few older studies report prevalence in pet cats to be between 2% and 10%.4–6 More recently, a study of pet cats in the UK7 reported a prevalence of 19%, although no information about the diagnostic methods used or the size of the study population was reported. A Romanian study8 reported a prevalence of 2% in a population of 4572 domestic cats. However, neither study considered the aetiology and/or the microorganisms involved in the development of otitis externa. Not much information is available about otitis externa in stray cats. Although it is considered the principal primary cause of feline otitis externa,1 there are surprisingly little data on the prevalence of Otodectes cynotis in stray cats and the prevalence reported varies between 0.6% and 37.0%.9–12 To our knowledge there are no studies about the prevalence of Malassezia species in the external ear canal of
either healthy stray cats or those with otitis, while the bacteria most commonly isolated by culture from the ears of feral cats are coagulase-negative staphylococci (with Staphylococcus felis/Staphylococcus simulans the most common) and Bacillus species.13 However, in that study, conducted in Grenada, neither ear cytology nor otoscopic evaluation were performed, and therefore the presence or absence of otitis externa could not be confirmed. Evaluation of the health status of free-roaming stray cats is important for the improvement of animal welfare14 and to obtain information about regional pathogens and diseases, regardless of their infectivity. Data on diseases in stray cat populations are needed to define their role in the transmission of some pathogenic agents Department of Veterinary Sciences for Health, Animal Production and Food Safety, University of Milan, Italy Corresponding author: Roberta Perego DVM, PhD, Department of Veterinary Sciences for Health, Animal Production and Food Safety, University of Milan, via Celoria, 10, 20133 Milan, Italy Email: [email protected]
Downloaded from jfm.sagepub.com at University of Birmingham on March 22, 2015
Journal of Feline Medicine and Surgery 0(0)
2 such as O cynotis, to other susceptible animals and domestic cats that have access to the outdoors.11,15–17 The aim of this study was to assess the prevalence of otitis externa in a population of stray cats of northern Italy and to evaluate the concordance of cytology and direct otoscopic examination as means of diagnosis of otitis externa. The study also characterises risk factors for feline otitis externa, including gender, age, habitat, season of sampling and microorganism identified at the ear cytology.
Material and methods Sampling and data collection Cases included 187 short haired stray cats from colonies in the Lombardy region of northern Italy, regardless of the presence/absence of signs of otitis externa. The cats were trapped by volunteers between 2008 and 2010, during a trap–neuter–return (TNR) programme approved by the city council, as previously described.15,16 Swabs were obtained from the external ear canal of each cat for cytological examination. The gender and habitat of each cat were recorded together with the data obtained from cytological ear evaluation. Age was estimated by dentition and animals were classified as young (⩽6 months of age) or adult (⩾6 months of age). To evaluate seasonal trends the samples were categorised according to the sampling period: spring samples (from March to May), summer samples (from June to August), autumn samples (from September to November) and winter samples (from December to February). For technical reasons, direct otoscopic assessment of the external ear canal was made in 86/187 cats, all from urban colonies. Evaluation included alterations of quantity and/or quality of ear wax (characterised grossly as normal or abundant and clear, yellow, brown or typically black with the presence of mites) and ear canal alterations (erythema, stenosis, ulceration). Cytological evaluation Samples for cytological evaluation were obtained with two sterile cotton swabs (one per ear) inserted into the lumen of the ear canal and swabbed against the surface of the vertical canal. Each cotton swab was rolled onto two clean microscope slides, evenly distributing a thin layer of material. One slide per ear was unstained, suspended with mineral oil and mounted with a cover slip, and one slide per ear was heat-fixed, stained with modified Wright’s rapid stain (Quick Panoptic Kit; Pokler Italia), suspended with mineral oil and mounted with a cover slip.2 Both slides were examined immediately. The unstained slide was scanned at low power (100×) for the presence of O cynotis, and the total number of mites was recorded. The detection of a single mite in at least one ear indicated the presence of infection in the cat.18
The stained slide was evaluated first at low power (100×) (to identify the areas of interest) and then under high power (400×) to evaluate the presence and number of microorganisms morphologically identifiable as Malassezia species and/or bacteria. As both bacteria and Malassezia species are common inhabitants of the normal feline external ear canal, a cytological score for the presence/absence of otitis in each cat was developed based on the average of the different values previously reported in the literature (Table 1).19–21 Briefly, each parameter evaluated microscopically (presence of cocci, rods and Malassezia species) was given a score from 0 (normal) to 2 (pathological) based on the mean number of detected microorganisms seen in 10 high-power dry fields (400×). Higher-power oil immersion fields (1000×) were chosen by scanning at low power until staining was visualised; by focusing on areas of staining, different kinds of bacteria (cocci or rods) were identified. A value score equal to 1 (or grey zone) is a cytological transitional zone proposed by previous authors20 in which other clinical criteria, including signs of otitis, are taken into account to make a diagnosis of otitis. Animals with a score in the grey zone were classified as normal because the number of microrganisms was lower than the clinically significant limit20 and clinical examination of the ears was not always possible. Cats were considered to be suffering from otitis externa when at least one of the evaluated parameters (cocci, rods and Malassezia species) had a cytological score of 2 in at least one ear. Statistical analysis Overall prevalence was defined as the percentage of cats diagnosed with otitis based on cytological examination of ear swabs. Prevalence data were regrouped according to age (young/adult), gender (male/female), pregnancy status (yes/no), habitat (urban/rural), season of sampling (spring/summer/autumn/winter), type of otitis based on microorganisms detected using ear cytology (Malassezia species/cocci/rods/Otodectes species). Univariate analysis of the categorical data was
Table 1 Cytological score based on the mean number of microorganisms identified in 10 different high-power dry fields (400×) Score 0 (Normal) Malassezia ⩽2 species (n°) Cocci (n°) ⩽4 Rods (n°) 0 *Ginel et al20
Downloaded from jfm.sagepub.com at University of Birmingham on March 22, 2015
1 (Grey zone)*
2 (Pathological)
>2 to 4 to
