Ear Canals Of Cats Research Articles

Comparative performance of video-otoscopy and CT in the diagnosis of external ear disease in cats.

The aim of the study was to compare CT with video-otoscopy for detecting external ear canal masses in cats and to describe CT features of feline external ear disease. This retrospective study evaluated the external ear canals of cats that underwent both CT and video-otoscopy. Two blinded observers reviewed the CT scans and their findings were compared with video-otoscopy results evaluated by one blinded observer. Of the 32 examined ears, 13 had an external ear canal mass detected by both CT and video-otoscopy. No false positives were identified. All 19 ears without masses were correctly identified as true negatives, resulting in perfect agreement for mass detection (kappa = 1.000). On histopathology, 9/13 masses were diagnosed as polyps, 1/13 masses was diagnosed as carcinoma, 2/13 did not undergo histopathology and 1/13 masses seen on video-otoscopy was diagnosed as otitis externa with granulomatous tissue formation. Of the 16 cats examined, 12 had a mass in the external ear canal diagnosed by video-otoscopy: six domestic shorthairs, five Maine Coons and one Oriental Shorthair cat. Of these cats, 11 had a unilateral mass and one had a bilateral mass. There was very low agreement between CT and video-otoscopy for ear canal wall enhancement and erythema (kappa = 0.033), as well as for ear canal thickening and stenosis (weighted kappa = 0.056). There was no significant difference between chronic and non-chronic clinical signs in terms of the presence of ear canal wall mineralisation (P = 0.223). There is high agreement between video-otoscopy and CT in detecting external ear canal masses in cats. However, there is very low agreement between CT and video-otoscopy for ear canal wall enhancement, erythema, thickening and stenosis. The presence of external ear canal mineralisation did not correlate with the chronicity of clinical signs.

Transcriptome Analysis of Otodectes cynotis in Different Developmental Stages.

The mite Otodectes cynotis is distributed worldwide and parasitism the ear canals of cats and dogs, causing otitis externa. Molecular biology of O. cynotis is poorly understood, with only a few genes being deposited in public databases. In the present study, we aimed to perform transcriptome analysis of O. cynotis using SMRT and Illumina sequencing of RNA from different development stages. SMRT-Seq of O. cynotis demonstrated 5,431 final transcripts, including 406 long non-coding RNAs and 2,698 differentially expressed genes (DEGs), including 1,357 up-regulated genes and 1,341 down-regulated genes between adult mites and nymph/larva. A total of 397 putative allergen genes were detected, 231 of which were DEGs. Among them, 77 were homologous of known mite allergens. The expression level of allergen genes hints at the pathogenicity of mites in different life stages, and the protein interaction network analysis could identify possible key genes in the pathogenic mechanism. Intriguingly, Gene Ontology analysis showed that most of the (DEGs) were associated with the terms hydrolase activity and proteolysis. Kyoto Encyclopedia of genes and genomes (KEGG) analysis identified drug metabolism-cytochrome P450 signal pathway as one of the top pathways. SMRT-Seq of the full-length transcriptome of O. cynotis was performed first, and a valuable resource was acquired through the combination analysis with the Illumina sequencing data. The results of our analyses provide new information for further research into Otodectes cynotis.

Prevalence and in vitro antifungal susceptibility of commensal yeasts in the external ear canal of cats

BackgroundLifestyle factors such as hair length, the frequency of ear cleaning and bathing, age, cat rearing, and sex may contribute to opportunistic yeast infections in the external ear canal of cats. This study aimed to determine the prevalence of commensal yeast organisms in cats’ external ear canals, evaluate their predisposing lifestyle factors, and test the susceptibility of Malassezia pachydermatis to antifungal agents.ResultsA total of 53 cats (33 male and 20 female) seronegative for feline leukemia virus and feline immunodeficiency virus were enrolled in this study. Their mean age (± standard deviation) was 6.04 (± 3.49) years. Fungal cultures and polymerase chain reaction tests were performed to identify the yeast species derived from the external ear canal. The association between lifestyle factors and the presence of M. pachydermatis was evaluated using Fisher’s exact test. The susceptibility of M. pachydermatis to antifungal agents was also analyzed. M. pachydermatis was the most frequently recovered yeast species, with a prevalence of 50.94 % (95 % confidence interval [CI]: 36.84–64.94 %). There was an association between hair length and a positive culture for M. pachydermatis (p = 0.0001). The odds of a negative culture for M. pachydermatis among short-haired cats was 11.67 (95 % CI, 3.22–42.24) times higher than that among long-haired cats (p = 0.0002). There was also an association between the frequency of ear cleaning and the presence of M. pachydermatis (p = 0.007). The odds of a negative culture for M. pachydermatis in cats that were receiving ear cleaning at intervals of ≤ 2 weeks was 5.78 (95 % CI, 1.67–19.94) times greater than that of cats receiving ear cleaning at intervals greater than 2 weeks or never (p = 0.0055). Ranges of minimum inhibitory concentrations (MICs) and minimum fungicidal concentrations for itraconazole, ketoconazole, miconazole, and terbinafine against M. pachydermatis were ≤ 0.063–4 and ≤ 0.063–≥32, ≤ 0.063–8 and 0.125–≥32, ≤ 0.063–≥32 and 0.5–≥32, and ≤ 0.016–1 and 0.125–8 µg/ml, respectively.ConclusionsM. pachydermatis was the most commonly identified yeast organism in the external ear canal of healthy cats. Hair length and the frequency of ear cleaning played a role in the colonization of M. pachydermatis. The M. pachydermatis isolates had various MIC levels for common fungicides.

Otoscopy and aural cytological findings in a population of rescue cats and cases in a referral small animal hospital in England and Wales.

Otitis externa is seen clinically in cats, although studies investigating this condition within the UK are lacking. The objective of this study was to investigate the prevalence of Otodectes cynotis mites and microbial infection in the ear canals of cats in various rescue centres and a referral hospital. Otoscopy was performed in 332 cats. Otoscopic findings were noted, including the gross visualisation of Otodectes species. A sample of cerumen was collected for cytological evaluation and a cerumen smear for detection of Otodectes mites if there was a large amount of aural exudate present. O cynotis infestation was noted in 3/341 cats (0.9%, 95% confidence interval [CI] 0.3-2.6). A total of 129/341 (37.8%; 95% CI 32.7-43.0) cats were found to have Malassezia species within one or both ears. Bacteria were found unilaterally in 9/341 (2.6%; 95% CI 1.4-4.9) cats. Analysis of the cytological findings showed an increased likelihood for Malassezia species to be present as age increased (n = 293; Pearson r = 0.204, P <0.001). There was also an increased likelihood of finding Malassezia species in both ears if found within one ear (n = 327; r = 0.499, P <0.001). There was a positive correlation between the number of Malassezia organisms and the quantity of aural exudate (n = 338; r = 0.778, P <0.001). Cats in which Otodectes species infestation were noted (n = 3) had moderate or large quantities of cerumen. This study shows that there was a low prevalence of O cynotis in this cohort of cats. In normal cats it was not unusual to find Malassezia microorganisms upon aural cytology, bacteria were noted far less frequently and in two cats this was associated with underlying anatomical pathology.

Otitis externa in the dog and the eat

Otitis externa is the most common disorder of the cat ear canal in small animals, with a higher incidence in dogs than in cats. It has a multifactorial etiology comprising of numerous predisposing, primary and perpetuating factors. The most important primary causes are atopy, food allergy, otodectic mange, foreign bodies, endocrinopathies and keratinisation disorders. Bacteria and yeasts residing in the ear canal usually complicate the initial lesions thus leading to the establishment of ceruminous or suppurative otitis externa. Otitis media and chronic hyperplastic changes of the ear canal are hold responsible for the perpetuation of the disease. A diagnosis is easily made from the history, the cleaning of the ear canal and otoscopy, the cytologic and parasitologic examination of ear exudates, the bacterial culture and sensitivity testing and the radiography (cartilage mineralization, otitis media). Evaluation and treatment of the underlying skin disease is always necessary. Therapy of otitis externa depends on identifying and controlling the predisposing and primary factors, whenever possible. Medical treatment includes cleaning of the ear canals and the middle ear, applying topicals and/or administering systemic medications (acaricides, antifungal agents, antibiotics, glucocorticoids). Corrective surgeries are indicated in the refractory to medical treatment cases.

Occurrence of Malassezia Species in Persian and Domestic Short Hair Cats with and without Otitis Externa

The yeasts of the Malassezia genus are opportunistic microorganisms in the skin and auricular canal of human and animals, mainly cats, and can cause otitis externa and dermatitis disorders. The aim of this study was to evaluate the occurrence of different species of Malassezia in the external ear canal of cats with and without otitis externa. Thirty-one normal cats and 82 animals with otitis externa were clinically examined. Sterile cotton swabs were used to collect specimens from the external ear canal and streaked onto the surface of Sabouraud dextrose agar (SDA) and modified Dixon agar. Malassezia yeasts were isolated from 95.1% and 48.4% of the cats with and without otitis externa, respectively. The rate of isolation in affected animals versus normals was highly significant (P<0.05). Out of the 137 isolates obtained from cats with otitis, 57.7% were identified as M. pachydermatis (with significant frequency; P<0.05), 15.4% as M. obtusa, 11.4% as M. globosa, 7.3% as M. slooffiae, 4.1% as M. sympodialis, 2.4% as M. furfur and 1.6% as M. restricta. Malassezia species were frequently isolated from subjects with age range from 1 to 4 years old (42.7%). Our finding of Malassezia isolates indicated that feline otitis externa can be associated with lipid-dependent Malassezia species in addition to the non lipid- dependent species M. pachydermatis.

Isolation of Malassezia pachydermatis and M. sympodialis from the external ear canal of cats with and without otitis externa

The objective of this study was to determine the presence of Malassezia spp. in the external ear canal of cats with and without otitis. Forty-five animals were studied, 20 with and 25 without otitis externa (OE). Cerumen or secretion from external ear canal samples was cultured on modified Mycosel agar and sterile olive oil was added to the surface of the medium before specimen seeding. The isolates were analysed for macro- and micromorphology and identified by catalase tests and on the basis of growth on Tween 20, 40, 60 and 80. Malassezia spp. were isolated from 15 out of 20 (75%) animals with otitis and from 7 out of 25 (28%) cats without OE; the difference between the two groups was statistically significant (P < or = 0.05). Malassezia pachydermatis and M. sympodialis were isolated from 60% (12/20) and 40% (8/20) of cats with otitis, respectively, with no significant difference in the frequency of isolation between the two species. In the microflora of the healthy ear canal M. pachydermatis was significantly more common (6/25, 24%) than M sympodialis (1/25, 4%). The present investigation confirms that M. sympodialis can also act as an aetiological agent of feline OE, and if commercial veterinary laboratories do not use media with added lipids for the isolation of Malassezia spp., this might lead to false-negative results.

Fine‐needle biopsy of external ear canal masses in the cat: cytologic results and histologic correlations in 27 cases

The cytologic diagnosis of ear canal tumors is difficult or impossible by swab alone because cell exfoliation may be poor and neoplastic cells may be masked by associated inflammation. Fine-needle biopsy (FNB) can be used to obtain a higher yield of cells for diagnosis. The purpose of this study was to assess the efficacy and diagnostic value of FNB and cytologic examination in providing an accurate diagnosis of masses growing in the external ear canal of cats. Cytologic specimens from masses in the external ear canal, taken under inhaled, general anesthesia, were classified into 4 groups: 1) ceruminous gland hyperplasia or adenoma, 2) ceruminous gland adenocarcinoma, 3) inflammatory polyps, and 4) other neoplastic and non-neoplastic masses. Cytopathologic diagnoses were compared with the final histopathologic diagnoses, and indices of diagnostic test accuracy (sensitivity, specificity, likelihood ratios, diagnostic-odds ratios) were calculated. Twenty-seven masses (from 25 cats, including 2 cats affected bilaterally) were included in the study. The results showed good correspondence between cytologic and histologic diagnoses with an overall agreement index (kappa) of .74, a diagnostic odds ratio of 22, and 100% (27/27) agreement in the diagnosis of inflammatory polyps versus neoplasia (both benign and malignant). FNB cytopathology of external ear masses in the cat was sufficiently accurate for distinguishing inflammatory polyps from neoplasia. For differentiation of benign proliferation and malignant neoplasia, however, histopathologic confirmation is recommended.

Isolation of Malassezia furfur from a cat.

During a survey of the occurrence of Malassezia species in the external ear canals of cats without otitis externa, Malassezia furfur was isolated. This is the first report of the isolation of M. furfur from cats.

Spatial distribution of sound pressure and energy flow in the ear canals of cats

Spatial pressure distributions have been measured in the ear canals of ten cats and analyzed to obtain the energy reflection properties of the middle ear over a 10- to 25-kHz range of frequencies. Considerable intersubject variability is observed, much of which can be correlated with the condition of the tympanic membrane. For ears judged to be in good condition, reflection coefficients typically take values of about 0.2 between 15 and 25 kHz, indicating good matching of the dynamical properties of the auditory system to the ear canal sound field. At lower frequencies, the reflection coefficients tend to be somewhat higher and at higher frequencies the reflection coefficients increase quite rapidly with frequency. For ears judged to be in poorer condition, energy reflection coefficients of 0.5 and 0.9 were determined for the 15- to 25-kHz range. The variations of sound pressure along the canal (about 10 dB, even in well-coupled systems) confirm that single point pressure measurements may be inappropriate for defining the acoustical input at higher frequencies and new measures for specifying the input should be investigated. The net flow of acoustic energy into the auditory system, the sound power, is one possibility. Some initial measurements of sound power, obtained from analysis of the spatial pressure distributions, are presented.

Measurements of distortion product phase in the cat ear canal

Amplitudes of odd-order distortion products (DPs) that are detected in animal ear canals have been used to probe cochlear health, to search for cochlear amplification, and to measure aspects of cochlear mechanical frequency response. The DP phase is also a rich source of information about cochlear mechanical response and reported here are extensive measurements of DP phase in the ear canal of cat. Much of the phase data can be explained by constant time delays that are a function of f2. When a1 (the amplitude of the f1 primary) is greater than a2 (amplitude of the higher frequency, f2, primary), both third-order and fifth-order DPs’ time delays are the same. In our preparations values are 0.6 ms at f2≳10 kHz; 0.8 ms at f2=5 kHz; 1.3 ms at f2=1 kHz. For the 2f1−f2 DP, as a2 becomes greater than a1 the time delays increase, even doubling at f2&amp;lt;2 kHz. The DP phase as a function of the DP frequency is generally dependent upon primary level. An interesting exception to this is that, for a1≳3a2, the phase of three DPs (2f1−f2, 3f1−2f2, and 2f2−f1) is independent of the a2 level.

On the passive power absorption potential of the eardrum

Experimental evidence reported by Khanna [Int. Cong. Acoust. B6‐4, Toronto (1986)] and Allen [Peripheral Auditory Mechanisms (Springer, New York, 1985), pp. 46–51] suggests that a very large fraction of the incident acoustic power in the cat ear canal is absorbed at the eardrum. In some animals, the high efficiency extends over a very wide frequency range from 300 Hz–30 kHz. These findings are sensitive to the condition of the animal and are subject to relatively large interanimal variations, particularly at high frequencies. Theoretical models describing the function of the middle ear differ significantly in predicting the power absorption and in predicting the fraction of the energy flux dissipated within the eardrum itself. Some insight into the behavior of the eardrum can be gained by studying the power absorption properties when the ossicular chain is immobilized or removed. In doing so, the dynamics of the ossicular chain, and to a large extent the dynamics of the cochlea, is removed from the system...

Sound propagation in the ear canal and coupling to the eardrum, with measurements on model systems.

A theoretical model of sound propagation in the ear canal is described, which takes into account both the complicated geometry of real ear canals and the distributed acoustical load presented by the eardrum. The geometry of the ear canal enters the theory in the form of a cross-sectional area function relative to a curved axis that follows the center of the ear canal. The tympanic membrane forms part of the ear canal wall and absorbs acoustical energy over its surface. Its motion leads to a driving term that must be added to the horn equation describing the pressure distribution in the ear canal. The sound field within the canal is assumed to be effectively one dimensional, depending only on longitudinal position along the canal. Experiments using model ear canals of uniform cross section were performed to test the ability of the theory to handle distributed loads. Sound-pressure distributions within each model canal were measured using a probe microphone. The behavior of the eardrum was simulated using either a distributed, locally reacting impedance or a mechanically driven piston. The agreement between theory and experiment is good up to a nominal upper frequency limit at which the ratio of canal width to wavelength is 0.25. It is estimated that the theory is applicable in ear canals of cats for frequencies at least as high as 25 kHz and in human ear canals to at least 15 kHz.

Coupling between ear canal and eardrum in model systems

This paper examines a theoretical model of sound propagation in the ear canal that accounts for the distributed acoustical load presented by the eardrum. This model is an extension of our previous one-dimensional formulation [S. M. Khanna and M. R. Stinson, J. Acoust. Soc. Am. 77, 577–589 (1985)], which was limited to rigid-walled canals. The spatially varying motion of the eardrum enters as a driving term in the equation for the sound field. In principle, this present model can be combined with detailed, dynamical models of the tympanic membrane. Experiments using model canals are underway to test the theory. In these, the sound field is determined with the eardrum replaced by either a mechanically driven piston or a passive, locally reacting load. Preliminary results indicate that the theoretical formulation can describe the sound field in the cat ear canal up to at least 25 kHz and in the human ear canal up to at least 15 kHz.

Short-term effects of sound exposure on the 2f1-f2 acoustic emission.

The 2f1-f2 acoustic emission (AE) was recorded in the ear canals of cats following exposure to tone bursts of 200-ms duration. Exposures known to result in short-term adaptation (i.e., adaptation lasting under 1 s) at the level of the auditory nerve failed to produce significant post-exposure changes in AE amplitude. Given the apparent cochlear origin of the 2f1-f2 AE, this result is consistent with the view that short-term adaptation in the auditory periphery does not involve substantial changes in cochlear mechanics.

Changes in the 2f1-f2 acoustic emission and whole-nerve response following sound exposure: long-term effects.

We examined the effects of 1-min tonal exposures on the amplitude of the 2f1-f2 distortion product in the ear canals of cats. These effects were compared with the changes in the whole-nerve action potential (AP) responses to tone bursts following similar exposures. Both the distortion product and AP amplitudes were reduced following exposure. The time courses of AP and acoustic emission (AE) recoveries were to a certain extent similar, and the post-exposure effects depended in similar ways upon the frequency and intensity of the exposure tone (adapter). Assuming that the 2f1-f2 AE is generated by nonlinearities in the motion of the cochlear partition, the reduction in its amplitude suggests that 1-min sound exposures can alter cochlear mechanics. The analogous aspects of the AP and AE post-exposure effects further suggests that components of long-term adaptation as measured by the AP are associated with changes in the mechanics of transduction. Finally, alterations of the middle ear cavities of the cat by opening the bulla or bony septum can result in marked changes in the effectiveness of an adapter in reducing AE amplitude.

Acoustic overstimulation reduces 2f1 − f2 cochlear emissions at low and high primary levels in the cat

The cubic distortion product, 2f1 − f2 (DP), was recorded in the cat ear canal as the level of two primary tones (f1 and f2,f1 <f2, L1 = L2) were varied from approximately 40 to 90 dB SPL. Primary frequencies were either 8.0 and 10.4 or 4.0 and 5.2 kHz. The DP level grows slowly at low primary levels and usually exhibits a sharp dip with primaries between 60 and 70 dB SPL. Above the dip, the growth is rapid, approaching a cubic relationship to the primary levels. After stimulation with a 90–100 dB SPL pure tone at f1 for 20–40 min, the auditory‐nerve responses to tone pips near f2 are reduced, indicating a threshold shift and sensorineural hearing impairment. In addition, the DP levels are altered at all primary levels. Below the original dip, it is frequently difficult to detect DP after overstimulation. A dip is usually seen at a higher level than before. At the highest primary levels used (90–100 dB SPL), DP levels are also significantly reduced. In similar experiments in the alligator lizard reported by Rosowski [J. J. Rosowski, W. T. Peake, and J. R. White, Hear. Res. 13, 141–158 (1984)], the growth of DP level with increasing primary level was similar to what we sec in the cat, but in the lizard only the DP generated at low levels were affected by overstimulation. We agree with their interpretation that the DP level function indicates several sources of cubic distortion which partially cancel at the dip. However, whereas the high‐level component appears to be resistant to overstimulation in the lizard, our data indicate that all components are susceptible to cochlear damage in the cat. [Work supported by VA.]

Adaptation of the acoustically emitted 2f1−f2 combination tone

Recent studies suggest that the 2f1−f2 ear‐canal distortion product is produced by nonlinearities in the motion of the cochlear partition. Given its cochlear origin, we attempted to use the acoustically emitted combination tone (ACT) to indirectly examine changes in cochlear mechanics that may be associated with long‐term adaptation (i.e., adaptation lasting several seconds) of eighth‐nerve responses. We examined the effects of 1‐min tonal exposures the amplitude of the 2f1−f2 ACT in the ear canals of cats. These effects were compared with post‐exposure changes in the whole‐nerve action potential (AP) responses to tone bursts that resulted from similar exposures. Both the distortion product and N1 amplitudes were reduced for several seconds following exposure. The reduction in ACT amplitude suggests that 1‐min exposures can alter cochlear mechanics. The fact that the same exposure tones cause reductions in N1 amplitude further suggests that neurally measured long‐term adaptation is linked to changes in th...

Inflammatory polypoid growths in the ear canal of cats

ABSTRACTThe characteristic clinical and pathological features of polyps of the ear canal as seen in 12 cats at the University of Pennsylvania Veterinary Hospital are described. In the authors' experience, and contrary to previous reports, inflammatory polyps are the commonest tumour of the feline ear and can be differentiated clinically from other neoplasms.

Effects of Eustachian Tube Ligation on Auditory Nerve Responses to Clicks

Auditory nerve responses to condensation and rarefaction clicks were recorded from the external ear canal of cats using a closed acoustic system. Repeated control recordings from both ears formed a baseline for each of four animals used in this study. After a baseline had been established, the Eustachian tube on one side was ligated and serial recordings of N1 responses were performed for up to 140 days postligation. By comparing the shift which occurred in the N1 latency-vs-click level plots after ligation, the equivalent hearing loss was determined. In all cases where the Eustachian tube was successfully ligated, the loss was progressive for the first 20 days, then usually showed some transitory improvement. The loss stabilized after 60 days, varying from 15 to 40 dB in different animals. In addition to N1 recordings, serial tympanograms were also measured. These indicated negative middle ear pressure in the first two days postligation and the presence of middle ear fluid by one week postligation.