Page 218 - WSAVA2018
P. 218

 25-28 September, 2018 | Singapore
positive IgE result remains controversial, but more recent studies demonstrate a positive correlation between disease severity (of AD) and Malassezia specific IgE titres. This has not yet been demonstrated in dogs. A therapeutic trial is warranted to determine the significance of the cytologic findings and results
in marked improvement with resolution of pruritus. Immunotherapy for Malassezia hypersensitivity is available although published studies are limited.
The diagnosis of Malassezia dermatitis is suggested by the typical history of regional pruritus and the presence of appropriate lesions in typical sites. A definitive diagnosis can be made by demonstrating excessive numbers of Malassezia organisms on the skin surface
or in the ears and observing a response to specific therapy. The most useful and readily available tool for the diagnosis of Malassezia dermatitis or otitis is cytology. Samples may be collected from the skin surface by a variety of methods, including direct impression smears, tape impression smears and dry cotton swabs, but the easiest to use is clear adhesive tape. Tape is preferred because the organisms are sometimes not located at
the surface of the lesions and repeated application of the tape to the same site will reveal deeper populations. The technique is quick and easy to perform and, with experience, tapes can be examined in the microscope and diagnosis made rapidly. The presence of numbers
of Malassezia greater than 2 per high power x1000 oil immersion field is suggestive of microbial overgrowth. Commonly populations are very much higher but the organisms may be found in clusters so at least 20 high power fields should be examined. For diagnosis of Malassezia paronychia, the broken end of a wooden cotton-tip swab can be used to scrape the claw fold,
and exudate is pressed and rolled onto a glass slide.
For examination of ear exudate in dogs and cats with ceruminous or exudative otitis externa, rolling of exudate in a thin layer on glass slides with a cotton-tip swab is the preferred method.
Malassezia dermatitis responds to topical therapy with antimicrobial shampoo agents containing chlorhexidine and miconazole (Malaseb®), piroctone olamine (Mediderm ®) or econazole (Sebazole ®).
It is critical that the owner is given adequate instructions when prescribing these products. They must be thoroughly massaged into the affected areas, including between the toes and in the axillae. The shampoo must be left in contact with the skin for 10 minutes before rinsing. Initially the shampoo should be used three times a week, until the condition has responded. At that time, repeat tape strips can be assessed to monitor
the improvement. If a good response is seen, the frequency of bathing can be reduced to twice and then once weekly. If the underlying problem is identified and controlled then it may not be necessary to continue long- term bathing. However if an underlying cause cannot be found, routine maintenance baths given one or twice a week can be used to keep the condition under control.
Localised areas of Malassezia dermatitis such as on the feet or lips can be treated with antifungal creams containing 2% miconazole (Daktarin ®) cream, 1% clotrimazole (Canesten®) cream or lotion), nystatin or terbinafine (Lamisil ®) or antifungal wipes containing 2% acetic acid, 2% boric acid q 12hrs or climbazole 0.5%/ chlorhexidine 3% pads q 24hrs (Biohex®).
Malassezia otitis usually responds well to treatment with otic drops containing clotrimazole (Otomax® Mometamax ®), miconazole (Surolan®), terbinafine (Osurnia®) or nystatin
(Canaural®) however it is very important to identify an underlying cause to prevent recurrence.
Systemic therapy
Systemic therapy for Malassezia infections may be required for severe cases or for those in which regular topical therapy is not practicable.
Ketoconazole, itraconazole, fluconazole and terbinafine
have all been reported effective. Ketoconazole used to be treatment of choice but this is no longer commercially available in Australia and has to be compounded.
*A low-dose regimen for large dogs using ketoconazole 5mg/kg q 12hrs PO for 10 days, followed by 5mg/
kg q 24hrs PO for 10 doses has been reported to be successful in the majority of cases, and lessens the expense of therapy.
** Itraconazole persists in the stratum corneum and therefore pulse therapy can be used. Dogs treated with 5mg/kg q 24hrs for two consecutive days followed by 5 days without treatment for 3 cycles (3 weeks) responded as well as dogs who had received the medication at 5mg/kg/day for 21 days (Pinchbeck 2002).
*** Anecdotal evidence suggests that fluconazole is not as clinically effective as the other azoles.
****Terbinafine given to dogs with Malassezia dermatitis at 30 mg/kg once daily for 3 weeks resulted in a similar improvement in cytological and skin lesion scores as in dogs given the drug at the same dose twice weekly for 3

   216   217   218   219   220