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Article

Treatment of feline otitis externa due to Otodectes cynotis and complicated by secondary bacterial and fungal infections with Oridermyl auricular ointment

Josée Roy, Christian Bédard, Maxim Moreau

Abstract — A blinded randomized study was conducted on 24 cats to confirm the presence of bacterial and/or fungal secondary infections associated with otoacariasis and to verify the efficacy of Oridermyl, an acaricidal/ antibiotic/antifungal/anti-inflammatory ointment, for treatment of the primary infestation and secondary infections. Sixteen cats were treated once daily for 10 d; 4 cats were not treated and 4 were treated with a placebo ointment. On Days 0 and 10, ears were swabbed for counts of bacteria and yeasts, for bacterial culture and sensitivity, and examined for determination of the degree of clinical otitis. Auricular secretions were removed for mite counts on Day 10, except for 8 treated cats that were done on Day 30. There was a high number of bacteria and yeasts in most cats and Oridermyl treatment significantly decreased those numbers. Staphylococci were the most frequently isolated bacteria. No live ear mites were found in cats treated with Oridermyl or the placebo ointment.

Résumé — Traitement de l’otite externe féline attribuable à Otodectes cynotis et compliquée par des infections bactériennes et fongiques secondaires à l’aide de l’onguent auriculaire Oridermyl. Un essai aléatoire à l’insu a été réalisé sur 24 chats pour confirmer la présence d’infections bactériennes et/ou fongiques secondaires associées à l’otoacariose et pour vérifier l’efficacité d’Oridermyl, un onguent acaricide, antibiotique, antifongique et anti-inflammatoire pour le traitement d’une infestation primaire et des infections secondaires. Seize chats ont été traités une fois par jour pendant 10 jours; 4 chats n’ont pas été traités et 4 ont été traités avec un onguent placebo. Les jours 0 et 10, des échantillons par écouvillons ont été prélevés pour obtenir des numérations de bactéries et de levures, pour une culture bactérienne et une épreuve de sensibilité et pour la détermination du degré de l’otite clinique. Des sécrétions auriculaires ont été prélevées pour les numérations d’acariens le jour 10, à l’exception des 8 chats traités pour lesquels les prélèvements ont été effectués le jour 30. Il y avait un nombre élevé de bactéries et de levures chez la plupart des chats et le traitement à l’aide d’Oridermyl a significativement réduit ces numérations. Les staphylocoques étaient les bactéries les plus fréquemment isolées. Aucun acarien vivant n’a été trouvé chez les chats traités à l’aide d’Oridermyl ou de l’onguent placebo.

(Traduit par Isabelle Vallières)Can Vet J 2011;52:277–282

Introduction

O todectes cynotis is thought to be responsible for 50% or more of feline otitis externa cases (1) and is considered to

be very contagious. This mite feeds on epidermal debris and tis-sue fluids from the superficial epidermis. Cats with infested ears

show pruritus in 41.5% of cases and abnormal auricular secre-tions in 85.4% of cases (2). Otodectes cynotis can cause a hyper-sensitivity reaction in some individuals (3,4). Irritation caused by the activity of O. cynotis added to a hypersensitivity reaction could lead to local inflammation severe enough to kill these parasites or to stimulate them to leave the ear (1). Moreover, modification of environmental conditions in the external ear canal could create disequilibrium in the normal bacterial and fungal flora, causing proliferation of some microorganisms and secondary bacterial and fungal otitis externa.

Traditionally, otodectic otitis was treated with repeated appli-cations of acaricidal auricular preparations. Some of these also contained antibiotic, antifungal, and anti-inflammatory agents. Dosage and duration of treatment for these medications were often determined empirically. Over the last 10 y, commercially available macrocyclic lactones revolutionized the treatment of this parasitic infestation, especially when spot-on and local preparations that needed to be applied only once demonstrated their efficacy against O. cynotis. However, macrocyclic lactones don’t treat secondary bacterial and fungal infections directly,

Vétoquinol Canada, 2000 ch. Georges, Lavaltrie, Quebec J5T 3S5 (Roy); Département de pathologie et microbiologie (Bedard) and GREPAQ, Département de biomédecine, Faculté de médecine vétérinaire, Université de Montréal, 3200 rue Sicotte, C.P. 5000, St-Hyacinthe, Quebec J2S 7C6 (Moreau).Address all correspondence to Dr. Josée Roy; e-mail: jroy@vetoquinol.caReprints will not be available from the authors.This study was supported financially by Vétoquinol Canada Inc.Use of this article is limited to a single copy for personal study. Anyone interested in obtaining reprints should contact the CVMA office (hbroughton@cvma-acmv.org) for additional copies or permission to use this material elsewhere.

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neither do they directly relieve the animal from local inflam-matory reactions (erythema, pruritus, pain, swelling) caused by the ear mites.

The objective of this study was to confirm the presence of secondary bacterial and fungal infections associated with otoacariasis and evaluate the efficacy of Oridermyl, an auricular ointment, for treatment of the primary infestation and second-ary yeast and bacterial ear infections.

Materials and methodsTwenty-four adult cats (13 males and 11 females) from a shel-ter for rescued cats were enrolled in this blinded randomized experimental study. To be included, cats had to be in good general health but affected by unilateral or bilateral otitis externa. Moving ear mites had to be visualized during otoscopic examination or live mites had to be found in auricular secre-tions examined under the microscope. Animals were kept in individual cages at the Complexe de Bioévaluation of the Faculté de médecine vétérinaire, Université de Montréal. A 12-day adaptation period preceded the study.

On Day -1, a randomization schedule was used to assign cats to the study groups. Cats were sorted first based on the presence or absence of live mites in ear secretions detected under the microscope, then on presence/absence of mites upon otoscopic examination, and finally upon the total clinical otoscopic score given to both ears. The 4 groups were randomly assigned to the first 4 cats having the most severe infestation. This was repeated until assignation of the 4 least severely infested cats. Random group assignation was performed to ensure homogeneous infes-tation level and disease score between treatment groups.

The 4 groups were as follows: 4 non-treated cats in Group A, 4 cats treated with an oil-based ointment (no active ingredient) in Group B, 8 cats treated with Oridermyl (Vétoquinol S.A., Magny-Vernois, France) for 10 d in Group C, and 8 cats treated with Oridermyl for 10 d and observed for 21 d after the end of treatment in Group D.

For 10 consecutive days a 0.3-mL volume of the auricular ointment with no active ingredient (group B) or Oridermyl ointment (groups C and D) was applied directly into both ears once each day. The ears were then massaged for approxi-mately 60 s to ensure adequate penetration of the ointment in the external ear canal. The cats were observed twice daily during the treatment period to detect any sign of toxicity of the test product. Hematology, serum chemistry, urinalysis, and physical examination were performed on Day -1 and Day 10. All laboratory analyses were performed by the labo-ratories of the Service diagnostic of the Faculté de médecine vétérinaire. The efficacy of Oridermyl (n = 16) was compared to that of a placebo ointment (n = 4), and no treatment (n = 4).

This study was approved by the Institutional Animal Care and Use Committee in accordance with the guidelines of the Canadian Council on Animal Care.

Test substancesOridermyl auricular ointment contained, per gram, 3500 units of neomycin sulphate, 100 000 units nystatin, 1 mg

triamcinolone acetonide, and 10 mg of permethrin in an oil base. The placebo ointment contained only the inactive ingre-dients of Oridermyl.

ParasitologyTo confirm infestation on Day -1, a small quantity of auricular secretion from each cat was harvested from each ear and exam-ined under the microscope. Under sedation, auricular secretion was completely removed to determine the total mite count at Day 10 (Groups A, B, and C) or at Day 30 (Group D). Using a cotton swab impregnated with mineral oil, the maximum pos-sible quantity of auricular secretion was collected from each ear. The auricular material was placed in a small bottle containing a small quantity of mineral oil. The cotton swab was also inserted into the bottle at the end of the procedure. To ensure retrieval of the maximum number of mites from the cotton swab, the latter was pulled apart in the mineral oil using tweezers. Samples were analyzed microscopically (403 or 1003 magnification) on the same day and the total number of live and dead adult mites per ear, the number of juvenile forms, and presence of eggs were recorded. Physical integrity and movement of mites were verified to establish if they were alive.

CytologyA sample was collected with a swab from the vertical portion of the external ear canal of both ears on Days 0, 10, and 30 (Group D only). Secretions were spread by gently rolling the swab onto a glass microscope slide. Samples were air dried, fixed, and stained with a modified Wright’s stain using a hematology slide stainer (Aerospray, Wescor, Logan, Utah, USA). Yeasts and bacteria were counted. A semi-quantitative evaluation as described by Ginel et al (5) was made, except a 5003 instead of a 4003 magnification was used. Cells were counted in 10 microscope fields and the average number of bacteria and yeast per field was calculated for each slide. For fields with more than 100 cells, data were reported as . 100.

BacteriologySamples for aerobic culture were collected from both ears on Days 0, 10, and 30 (Group D only) using a commercial culture medium (BBL CultureSwab, BD, Franklin Lakes, New Jersey, USA). Each isolate was identified and its relative abundance estimated (score 1–4). The samples were streaked on Columbia agar supplemented with 5% sheep blood. Plates were incubated at 35°C in aerobic conditions with 5% CO2. Plates were read after 24 h and 48 h. Standard bacteriologic techniques were used to identify aerobic bacteria. Strains were frozen in tryp-ticase soy broth (Difco Laboratories, Detroit, Michigan, USA) 1 10% glycerol at 270°C until antimicrobial sensitivity tests were performed.

In all groups, sensitivity to neomycin was tested for each dis-tinct bacteriological isolate. When the same bacterial species was identified in both ears, only 1 isolate was tested. Only isolates having grown within the first 24 h of incubation were tested. Sensitivity testing was done by the agar gel diffusion method fol-lowing the Clinical and Laboratory Standards Institute (CLSI) guidelines (M31-A3, vol. 28 No. 11). Bacterial suspensions

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used for inoculation of the MIC panels were prepared as per CLSI guidelines. Three to 5 colonies were removed from the surface of an 18 h culture of the organism using a sterile swab and suspended in 5 mL of saline. This bacterial suspension was adjusted to a 0.5 McFarland standard and used to inoculate a Mueller-Hinton agar plate in order to obtain confluent growth. A disc of neomycin (30 mg) was laid on the plate, which was incubated at 35°C in air for 20 to 22 h. After incubation, the size of the inhibition zone was measured and compared to the standards of the CLSI guidelines to determine the sensitivity or resistance of isolates.

Standard sensitivity testing with 12 antimicrobials by the agar gel diffusion method following the CLSI guidelines M31-A3 was done on 5 isolated Staphylococcus aureus that were kept frozen.

Clinical efficacyVarious observations were made to evaluate the patient’s local response to Oridermyl. An otoscopic examination was done by a veterinary dermatologist on Days 0, 10, and 30 (Group D only), and a score was attributed for the approximate number of visible mites. The appearance of the external ear canal and the inner pinna was noted (erythema, ulceration, pruritus, type and quantity of secretion, pain at palpation). Each criterion was attributed a score on a scale from 0 to 3, the lowest score corresponding to a condition typically observed in a cat with clinically normal ears. The scoring chart is shown in Table 1. The total otoscopic clinical score was calculated for each ear by adding the individual scores for erythema, ulceration, pruritus, pain, type, and quantity of secretion.

Statistical analysisStatistical analyses were performed using SPSS statistical soft-ware. Two preliminary repeated measures analysis of variance were performed to identify possible differences between the ears for the various Oridermyl groups, and potential interaction with the other effects of interest. Subsequently, a repeated measures analysis of variance with interaction term was performed to study only the following 2 effects: GROUP (3 levels, namely

No-treatment, Placebo, and Oridermyl) and TIME (2 levels, Day 0 and Day 10) on 3 variables: the mean number of bacteria per high power field (hpf ), the mean number of yeasts per hpf, the mean total otoscopic score. The significance level was set at P = 0.05.

ResultsParasitologyLive mites were not observed after the end of treatment in any cat treated with Oridermyl. Results for means of live, dead, and juvenile mites are presented in Table 2. In the placebo ointment group (B), all cats were free of live mites at Day 10, but dead mites were observed in 1 cat and eggs were noted in another cat. Eggs were absent from all except 1 ear of Oridermyl-treated cats at Day 10 (Group C) and completely absent from all ears at Day 30 (Group D). Eggs were present in 7 of the 8 non-treated ears (Group A) at Day 10.

CytologyBefore treatment (Day 0), all 24 cats had a bacterial or a fungal infection according to cytological examination of ear secretions. The mean number of bacteria was . 100 bacteria per field in 23 cats in 1 (2/23) or 2 ears (21/23). The other cat had a mean count of bacteria per hpf of 76.4 in the right ear and 67.4 in the left ear. Similarly for yeasts, 20 cats had a mean number per hpf over 100 yeasts per hpf, in 1 (8/20) or 2 ears (12/20).

Results presented in Table 3 demonstrate the antifungal and antibacterial effects of Oridermyl compared with pre-treatment values and to control groups. After the end of the treatment (Day 10), there was a significant reduction in the mean num-ber of bacteria and yeasts in treated animals (C and D groups together) compared with non-treated (A) and placebo-treated (B) groups. Statistically, the data show interaction between treat-ment and time effects (P , 0.001 for bacteria and P = 0.038 for yeast). After a marginal analysis of each effect separately, we concluded that at Day 0, the 3 groups have statistically similar values (P = 0.596 for bacteria and P = 0.687 for yeast), but there is a statistically significant ordering of the 3 groups at Day 10,

Table 1. Scoring scheme for severity of clinical otitis based on otoscopic examination

Score 0 1 2 3

Visible mite score No mites seen , 5 mites seen 5 to 10 mites seen . 10 mites seen

Erythema Absent Mild Moderate SevereUlceration Absent Mild Moderate SeverePruritus Absent Mild Moderate SeverePain Absent Mild Moderate SevereQuantity of secretion Normal Slight increase Moderate increase Markedly increasedType of secretion Normal Brownish, granular Brownish, waxy Purulent

Table 2. Mean number of mites per ear at Day 10 (Groups A, B, and C) or Day 30 (Group D)

Mean number of Mean number of Mean number ofTreatment group live mites (Sx̄ ) dead mites (Sx̄ ) juvenile forms (Sx̄ )

A (no treatment, n = 8) 27.5 (11.4) 14.5 (4.7) 18.1 (8.1)B (placebo, n = 8) 0.0 (0.0) 3.5 (2.6) 0.0 (0.0)C (Oridermyl, n = 16, Day 10) 0.0 (0.0) 0.4 (0.3) 0.0 (0.0)D (Oridermyl, n = 16, Day 30) 0.0 (0.0) 0.0 (0.0) 0.0 (0.0)

(Sx̄ ) — standard error of the mean.

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namely: No treatment . Placebo . Oridermyl (P , 0.001) for bacteria and Placebo . No Treatment . Oridermyl (P , 0.001) for yeast. Furthermore, there was a significant dif-ference (P , 0.001) in mean number of bacteria and yeasts in Oridermyl-treated groups when pre and post-treatment results were compared [Day 0 versus Day 10 (groups C and D sepa-rately and together)] and Day 0 versus Day 30 (Group D only).

BacteriologyThe following bacteria were isolated at Day 0 from the 48 ears (24 cats): hemolytic Staphylococcus spp. (40/48, 23 cats), non-hemolytic Staphylococcus spp. (30/48, 19 cats), Corynebacterium spp. (23/48, 13 cats), Pseudomonas aeruginosa (5/48, 4 cats), Enterococcus spp. (3/48, 2 cats), Staphylococcus aureus (2/48, 1 cat) and Klebsiella (1/48). In Oridermyl-treated cats (Groups C and D), the frequency of isolation at Day 10 compared with pre-treatment decreased as follows: from 26 to 18 positive ears for hemolytic Staphylococcus spp., from 19 to 2 positive ears for non-hemolytic Staphylococcus spp., and from 13 to 1 positive ear for Corynebacterium spp. Interestingly, P. aeruginosa was not isolated at Day 10 in 2 of the 5 ears that were previously positive.

All except 1 Staphylococcus spp. isolated during the study and for which sensitivity to neomycin was verified were sensitive to this antibiotic (66/67). Among 6 Pseudomonas aeruginosa isolates tested, 4 were of intermediate sensitivity and 2 were resistant. All 6 S. aureus and 2 Enterococcus spp. tested were resistant to neomycin. All 5 S. aureus that were kept frozen and subsequently tested were resistant to ampicillin, cefoxitin, clindamycin, enrofloxacin, erythromycin, orbifloxacin, and penicillin. Furthermore, 4 isolates were resistant to ampicillin– clavulanic acid, and 1 isolate to tetracycline.

Clinical efficacyPrior to treatment, mild to severe pruritus (23/24 cats), mild erythema (14/24), and increased quantity of secretion (24/24) were observed in 1 or both ears of each cat. Ulceration was never observed and pain was detected in 1 cat. Purulent secretion was seen in 1 case whereas secretions were brownish and granular in at least 1 ear of all 24 cats (44/48 ears).

Table 4 shows means for visible mite score and total otoscopic clinical score in the different groups. Mites were not seen after treatment in the Oridermyl-treated cats and in ears treated with the placebo ointment. The data for total otoscopic clinical score show statistically significant interaction between the treatment and time effects (P , 0.001). After a marginal analysis of the effects separately, we conclude that there was no statistically significant difference between the groups at Day -1 (P = 0.770), but that a statistically significant difference existed at Day 10 (P , 0.001). A more precise analysis indicates a partial ordering, namely: No treatment . Placebo = Oridermyl.

DiscussionAn auricular ointment containing 1% permethrin was efficacious against O. cynotis in the present study in which it was applied in feline ears once daily for 10 d. However the placebo oint-ment containing no acaricidal agent was also efficacious against O. cynotis for the 4 treated cats. One possible explanation would be that the ointment’s oily base killed the mites as previously suggested (6). An antifungal-antibacterial-anti-inflammatory oily base auricular preparation with no known acaricidal agent was effective against O. cynotis infestations in dogs and cats when applied twice daily for 7 d (6). In 2000, Engelen and Anthonissens also showed the efficacy of 2 auricular preparations

Table 3. Mean numbers of bacteria and yeasts per high power field (5003) at cytology

Day 0 Day 10 Day 30

Mean number Mean number Mean number Mean number Mean number Mean number of bacteria of yeasts of bacteria of yeasts of bacteria of yeastsGroup per hpf (Sx̄ ) per hpf (Sx̄ ) per hpf (Sx̄ ) per hpf (Sx̄ ) per hpf (Sx̄ ) per hpf (Sx̄ )

A (no treatment, n = 8) 90.5 (9.5) 73.6 (15.3) 99.1 (0.9) 26.5 (11.7) NA NAB (placebo, n = 8) 100.0 (0.0) 84.6 (11.2) 35.1 (14.6) 56.2 (12.2) NA NAC (Oridermyl, n = 16, No follow-up) 100.0 (0.0) 82.7 (8.1) 1.4 (0.2) 2.4 (0.5) NA NAD (Oridermyl, n = 16, 90.4 (6.3) 58.3 (12.1) 0.7 (0.3) 0.1 (0.0) 3.0 (1.4) 1.3 (0.9) Follow-up until Day 30)

hpf — high power field.(Sx̄ ) — standard error of the mean.NA — not applicable.

Table 4. Means for visible mite scores and total otoscopic clinical scores

Day -1 Day 10 Day 30

Mean total Mean total Mean total Mean visible otoscopic Mean visible otoscopic Mean visible otoscopicGroup mite score (Sx̄ ) clinical score (Sx̄ ) mite score (Sx̄ ) clinical score (Sx̄ ) mite score (Sx̄ ) clinical score (Sx̄ )

A (no treatment, n = 8) 1.0 (0.4) 5.5 (0.2) 2.1 (0.4) 6.9 (0.9) NA NAB (placebo, n = 8) 1.9 (0.4) 5.1 (0.4) 0.0 (0.0) 2.6 (0.6) NA NAC (Oridermyl, n = 16, No follow-up) 1.7 (0.3) 4.8 (0.3) 0.0 (0.0) 2.4 (0.4) NA NAD (Oridermyl, n = 16, 1.4 (0.3) 5.4 (0.4) 0.0 (0.0) 2.7 (0.3) 0.0 (0.0) 1.6 (0.4) Follow-up until Day 30)

(Sx̄ ) — standard error of the mean.NA — not applicable.

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without acaricidal agent for treatment of feline and canine otoa-cariasis (7). The mechanism of action of this acaricidal effect is unknown but we hypothesize that coating the mites with an oily preparation may prevent them from maintaining their vital func-tions. This implies that the volume of ointment applied and the frequency and duration of treatment could be critical.

Yeasts were identified as Malassezia spp. based on their mor-phology observed at cytology. A mean number of # 0.53 yeast per hpf (400X) is observed in a normal feline ear and $ 23.69 yeasts in a pathological condition (5). Using these cut-off values, only 1 of the 24 cats in the present study had 2 uninfected ears and 21 had at least 1 infected ear at the beginning of the treatments. After 10 d of treatment with Oridermyl, none of the 16 cats had diseased ears, whereas 3 non-treated cats and the 4 placebo oint-ment treated cats still had at least 1 diseased ear. These results indicate that cats with otoacariasis may also suffer from fungal otitis externa and confirm the efficacy of the antifungal treatment to resolve the secondary infection.

Mean bacterial counts per hpf for auricular cytology observed by Ginel et al (5) were 1.78 bacteria per microscope field (4003) in clinically healthy cats and 31.13 in cases of otitis externa. In the present study at Day 0 all cats were suffering from bacterial otitis externa in at least 1 ear according to these values. None of the Oridermyl-treated cats had otitis externa at Day 10, whereas the 4 non-treated cats and 2 of the placebo ointment treated cats had. It can be concluded that cats infested by O. cynotis in the present study also suffered from bacterial infections. The auricular ointment used in this study enabled a return to values more compatible with a bacterial flora normally found in a clinically healthy feline ear.

A decrease in the magnitude of fungal overgrowth from Day 0 to Day 10 in the non-treated and placebo groups and an apparent mild antibacterial effect of the placebo ointment were unexpected. In a study on the efficacy of Oridermyl against otoacariasis in which a control (non-treated) group was included, semi-quantitative microbiological culture showed no decrease in yeasts and staphylococci from Day 0 to Day 22 for non-treated cats and a significant antifungal and antibacterial effect for treated animals (unpublished data, Vétoquinol S.A.). The present study included a limited number of control animals and further experimental work is needed. It is plausible that elimination of the primary cause of otitis externa (O. cynotis) by the placebo ointment would decrease the local inflammatory response and consequently enable a return to normal levels of bacteria and yeasts with time.

Staphylococci were the bacteria most frequently isolated from cats’ ears infested with O. cynotis; this is consistent with previous reports on cats suffering from otitis externa (8,9). Pasteurella was not isolated in the present study, although this species represented almost 15% of bacteria isolated from feline otitis externa in 1 study (9). Staphylococci, streptococci, and Corynebacterium spp. are found in small numbers in healthy canine and feline ears (10) and evidently proliferate in disease.

Neomycin, an aminoglycoside, is frequently used topically as first line medication against gram-positive cocci. In 1 study 88.5% of S. intermedius isolated from the external ear canal of dogs with chronic otitis were sensitive to neomycin (11).

Hariharan et al (9) reported that all coagulase-negative staphylo-cocci isolated from feline otitis were sensitive to the aminoglyco-side amikacin whereas 12% of coagulase-positive staphylococci (including S. intermedius and S. aureus) were resistant. In the present study, all isolated hemolytic Staphylococcus spp. tested were sensitive to neomycin, whereas all S. aureus were resistant.

The 5 isolated S. aureus were multidrug resistant, including resistance to cefoxitin which is used by the laboratory as an indicator of potential resistance to methicillin. Polymerase chain reaction assays for the mecA gene would have determined if these isolates were really methicillin-resistant.

Before treatment, inflammation of the external ear canal and inner pinna was present in cats of all 4 groups. In Oridermyl-treated groups, signs of inflammation were minimal at Day 10 and a significant improvement was noted in terms of decreased pruritus and erythema compared to Day -1 and to the non-treated group. This decrease in inflammation may be attributed to elimination of mites and/or the control of bacterial or yeast infections. However, there was no significant difference in total otoscopic clinical score at Day 10 between Oridermyl-treated and placebo ointment-treated cats. Using a treatment that com-bines acaricidal, antibiotic, antifungal, and anti-inflammatory agents is expected to result in significant relief of symptoms. Comparison with the untreated animals indicated that this occurred. The fact that there was no difference in the clinical results between the drug-treated and the placebo-treated cats may be due to the acaricidal effects of the ointment used for the placebo.

To conclude, the present study confirmed the presence of bacterial and fungal infections or overgrowth in association with feline otoacariasis and showed that Oridermyl auricular ointment was effective in treating the primary infestation and its consequences in the ears.

AcknowledgmentsThe authors thank Dr. Alain Villeneuve, Dr. Serge Messier, Dr. Frédéric Sauvé, Mr. Robert Bilinski, and Dr. Charlotte Thorneloe for their participation in this study, and Vétoquinol Canada Inc. for financial support. CVJ

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8. Bensignor E. Diagnostic approach to otitis externa. In: Guaguère É, Prélaud P, eds. A Practical Guide to Feline Dermatology. Lyon, France: Mérial, 1999:22.1–22.8.

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Practical Small Animal MRI

Gavin PR, Bagley RS. Wiley-Blackwell, Ames, Iowa, USA. 2009. ISBN 978-0-8138-0607-5. US$174.99 362 pp.

P ractical Small Animal MRI is a timely addition to the ever-expanding literature on veterinary imaging. Magnetic

resonance imaging is considered the “gold-standard” in soft tissue imaging and this text is an excellent compilation of MRI images and anatomic illustrations. This book not only covers the common neurological applications of MRI but also provides a good reference for musculoskeletal, thoracic, and abdominal MRI imaging. The inclusion of images and discussion of nor-mal anatomy in each section are invaluable. The first chapter

provides a ready reference of technical details, including basic physics, MRI sequences, and artifacts in an easy to comprehend style. Future editions could be improved by providing references or suggested reading lists for chapter 1 and numerical references within the text. In a few instances, pathophysiology is discussed but details of the imaging findings are lacking (e.g., discussion of reversible MRI changes associated with seizures). Practical Small Animal MRI will serve as a valuable reference for veterinarians involved with MRI imaging, such as veterinary radiologists, neurologists, residents, and interns.

Reviewed by Ajay Sharma, BVSc&AH, MVSc, DVM, DACVR, Associate Professor, Veterinary Medical Imaging, Western College of Veterinary Medicine, Saskatoon, Saskatchewan S7N 5B4.

Book ReviewCompte rendu de livre