Otitis Externa: Pathogenesis, Treatment & Preventative Maintenance. All photos are copyright of CE Griffin, REW Halliwell, DN Carlotti & DH Lloyd

Transcription

1 Otitis Externa: Pathogenesis, Treatment & Preventative Maintenance All photos are copyright of CE Griffin, REW Halliwell, DN Carlotti & DH Lloyd

2 Anatomy Cartilage Ear canal Tympanum

3 Otitis externa Inflammation & infection of the ear canal

4 Pathogenesis INFLAMMATION Epidermal hyperkeratosis & sebaceous glands hyperplasia Increased desquamation & sebaceous secretion INFECTION Accumulation of cerumin & debris

5 Pathogenesis Predisposing factors Primary factors Multifactorial Perpetuating factors

6 Pathogenesis Predisposing factors Factors that alter the environment of the ear canal, making the latter more susceptible to bacterial & fungal infections. On their own, these factors do not give rise to otitis externa. No treatment is possible, only preventative maintenance.

7 Pathogenesis Predisposing factors Abnormal anatomy Excessive moisture Treatment errors Neoplasm Polyp

8 Pathogenesis Primary factors On their own, these factors can induce or initiate otitis externa. Treatment is possible for some of the factors but requires patience and step-wise approach to establishing them.

9 Pathogenesis Primary factors Parasites Allergies Defective keratinisation Foreign bodies Onset: erythema

10 Pathogenesis Primary factors Parasites : Otodectes cynotis Extremely contagious. Only a small number of mites are needed to trigger the disease, through induction of an allergic reaction. In recurrent cases, consider the presence of asymptomatic carriers of ear mites in the same household. Otodectes cynotis: black cerumin

11 Pathogenesis Primary factors Allergies: 30% of allergy cases, otitis externa is the initial and only clinical sign detected. 83% of animals with atopy have concurrent otitis externa. Atopy 80% of animals with food allergy have concurrent otitis externa. Up to 90% of animals with FAD have concurrent otitis externa.

12 Pathogenesis Primary factors Defective keratinisation: Genetic disorder of certain breeds like Boxer, Cocker Spaniel, Doberman, German Shepherd Dog. Epidermal hyperkeratosis, sebaceous gland hyperplasia. Defective cerumin (increase in free fatty acids and deesterified wax). Cocker spaniel

13 Pathogenesis Primary factors Foreign bodies: Plant materials. Excessive hair. Dried-up medication, e.g. ointment. Dirt and sand particles. Grass awn

14 Pathogenesis Perpetuating factors These factors will not initiate the onset of otitis externa, but will prevent its resolution. They are bacteria & yeast. Up to 50% of a healthy ear have a positive culture of a variety of commensal and potentially pathogenic bacteria. Treatment is of prime importance for the veterinarian.

15 Pathogenesis Perpetuating factors Organism 1. Malassezia spp. 2. Staphylococcus coagulase + 3. Pseudomonas 4. Proteus 5. Streptococcus 6. Gram ve bacteria Occurrence 30% 30% 20% 10% < 5% < 5% 90% Shipstone in ASAVA Conference (2000)

16 Diagnosis Otoscopic examination Perform an otoscopic examination of the ear canal precedent to a dermtological examination. Sedate or anesthetize animal if necessary (proper restraint will prevent further damage of the ear canal). Perform examination under bright florescence lighting.

17 Diagnosis Otoscopic examination Important changes to note: Type of pinnae Degree of erythema & edema Presence of proliferative changes in the canals, or foreign bodies or parasites. Diameter of canals. Nature of discharge. Integrity of tympanum.

18 Diagnosis Otoscopic examination Impact of the middle ear: Head tilt or facial nerve damage. Prognosis guarded.

19 Diagnosis Cytology Incorporate in the practice for all cases of otitis externa. Simple and valuable tool. Repeat at subsequent visits, always. Legitimate supplemental income for the practice. Organism Sensitivity of detection 1. Gram +ve 2. Gram -ve 3. Malassezia 84% 100% 100% Shipstone in ASAVA Conference (2000)

20 Diagnosis Cytology : ear mites Otodectes cynotis in oil immersion

21 Diagnosis Cytology : cocci Neutrophils Intracellular cocci

22 Diagnosis Cytology : Malassezia Budding cells

23 Diagnosis Culture & sensitivity tests Expensive and no more valuable than cytology. Not indicated at first visit or first occurrence of otitis externa. Can be considered in chronic and recurrent cases, or when there is real failure to respond to therapy.

24 Diagnosis Thorough cleansing of ear Otoscopy & Cytology Bacteria & Yeast Involvement of O. cynotis only Topical & systemic therapy Topical therapy only Relapse Poor response Good response CURE Otoscopy, Cytology, C&S Test. Further cleansing. Continue treatment regimen. Initiate preventative maintenance. Reassess the P 3 Reassess treatment regimen

25 Treatment 3 majors stages 1) Ear cleaning with management of the predisposing causes 2) Treatment of perpetuating causes 3) Identification and treatment of primary causes

26 Treatment 1) Ear cleaning and predisposing causes Importance of ear cleaning: remove irritating agents facilitate the contact between the medicament and the ear canal wall reduce microorganisms proliferation Conditions for cleaning: Under general anesthesia : ideal If anesthesia is not possible (refused by the owner, current health state of the animal, not severe canal occlusion and exudate) utilisation of products with both cleansing and drying properties. Predisposing causes : Surgical removal (abnormal anatomy, neoplasm), cleasing/drying agent (excessive moisture), rechecking (treatment error)

27 Treatment 2) Treatment of perpetuating causes Requirement: Efficacy against bacteria and/or yeast Reduction of the inflammation (corticosteroids) Conditions of treatment: Essentially topical treatments (twice daily) Clinic and microscopic examination after 15 days Keep the ear clean (see above, Ear cleaning )

28 Treatment 2) Identification and treatment of primary causes Parasites: acaricides effective against Otodectes or Demodex (rarely) Allergies: The ear s problem is a part of a general disease (Cf allergies treatment) Defective keratinisation: Mostly caused by an idiopathic seborrhea (long term corticosteroids therapy), sometimes endocrinopathy (hypothyroidism) Foreign bodies: Light surgery (NB : both ears must be examinated)

29 Treatment Eliminating the inflammation Corticosteroids are the drug of choice for topical therapy. High anti-inflammatory (A.I.) activity is desirable for rapid remission and better pet owner compliance. Longer biological half-life ensures that the A.I. activity is prolonged and the dose used is small to avoid side effects.

30 Treatment Eliminating the inflammation Corticosteroid A.I. Activity Biological Half-life Hydrocortisone Prednisolone Triamcinolone Dexamethasone Betamethasone hrs hrs hrs hrs hrs W.B. Saunders Co. in Current Veterinary Therapy (1995)

31 Treatment Eliminating the infection Antibiotics Proteus Pseudomonas Staphylococcus Amipicillin R R S/ R Chloramphenicol R S/ R S Gentamycin S S S Neomycin S/ r S/ r S Penicillin R R R Polymyxin B S/ r R S Streptomycin s/ R s/ R S Tetracycline s/ R s/ R S W.B. Saunders Co. in Current Veterinary Therapy (1995)

32 Treatment Eliminating the infection Broad spectrum antibiotic that can eliminate Staphylococcus, Pseudomonas and Proteus. Gentamycin Fungicide to eliminate the Malassezia. Acaricide to eliminate the ear mites. } Thiabendazole

33 Preventative Maintenance In the majority of cases, the permanent correction of predisposing and certain primary factors is not possible: Abnormal anatomy Excessive moisture Atopy Defective keratinisation

34 Preventative Maintenance The purpose of preventative maintenance is to reduce the risk of recurrence and to reinforce the benefit of therapy. The pet owner should perceive that his/her efforts and money dispensed in treating the pet is not diminished by frequent recurrences.

35 Preventative Maintenance Preventative maintenance of the ear should therefore include: Regular clipping of the hair on the inside of the pinnae. Gentle plucking of excessive hair. Routine use of a well adapted cleansing agent to minimize build-up of the perpetuating factors.

36 Preventative Maintenance Criteria for choosing a cleansing agent It is beneficial to the pet that is strongly predisposed to otitis externa to have its ear canals cleansed regularly, as this will minimize build-up of the perpetuating factors. This can be done after every shampooing to ensure that no excessive moisture is left behind in the ear canal to cause maceration, excessive production of cerumin and subsequent inflammation.

37 Preventative Maintenance Criteria for choosing a cleansing agent Mildly ceruminolytic for frequent usage: propylene glycol, lactic acid Mildly drying so as not to be irritating: sodium ducosate Mildly keratolytic so as to reduce excess cerumin: lactic acid, salicylic acid Antiseptic to control the bacteria & yeast population: lactic acid, parachlorometaxylenol Non-traumatic for the pet: self-cleaning fluid

38 Preventative Maintenance Combination of active agents DH Lloyd et al., 1998, Vet. Rec., 143: The cleansing agent clearly has potent antimicrobial activity.( ). It is likely that the low ph created by the lactic and salicylic acid is involved in its antimicrobial action but the antibacterial and antifungal activity of propylene glycol and parachlorometaxylenol may also be important. Penetration of these agents is probably facilitated by the surface active properties of sodium ducosate.