Episode 20 - We’ve Been Expecting You, Malassezia

Chapter 1: "The Dermatological Agent: Ross's Malassezia Mission"

 

02.42 - John begins by welcoming Ross to the Skinflint podcast and acknowledges Ross's expertise in "Malassezia." He asks Ross to share his background and explain what Malassezia is.

 

Ross introduces himself as a professor of veterinary dermatology, detailing his experience in farm practice and later transitioning to small animal practice. He pursued further studies and a Ph.D. specifically focusing on Malassezia, and so has been interested in them for more than 30 years.

 

03.44 - John asks Ross to elaborate on Malassezia, describing it for listeners who might not be familiar with the term.

 

Ross explains that Malassezia is a group of yeast found naturally on the skin of various mammals and birds, thriving in lipid-rich environments. It typically exists as a commensal organism on the skin but can become an opportunistic pathogen, leading to dermatitis and otitis in dogs and occasionally in cats and horses.

 

05:27 - Sue asks if Malassezia is the same across different species or if there are variations.

 

Ross explains that there are 18 known species of Malassezia, each potentially adapted to a specific host. He discusses examples like M. cunicui in rabbits, M. caprae in goats, and M. equina in horses. He notes M. pachydermatitis as the dominant species in dogs, which is unique as it can grow on routine culture media, unlike other species requiring lipid supplementation. In contrast, cats may have different species like M. nana and M. slooffiae, among others, leading to variations in yeast colonisation. There's a discrepancy between what's identified molecularly and what's observed in cultures, particularly in dogs, highlighting an unexplained scientific disparity.

 

 

Chapter 2: "Species Confidential: Malassezia's Breed of Intrigue"

 

8.44 - John asks Ross about the location of Malassezia on animals.

 

Ross mentions that, in dogs, Malassezia is predominantly found in web spaces (75-80%), lip fold regions (similar proportion), and ear canals (about one-third). Lower levels are detected on the trunk, axilla, groin, and dorsum due to their warm, moist nature.

 

10.00 - John inquires about identifying Malassezia in cytology with dermatology tests like tape strips or impression smears.

 

07:35.54 - Ross confirms that Malassezia has a characteristic peanut-shaped morphology, identifiable under microscopy, usually abundant in specimens obtained from areas like a friendly basset hound's ear wax or neck fold wax, which are good teaching examples.

 

08:17.63 - Sue asks Ross about determining the relevance of Malassezia presence in ears or skin.

Ross explains breed-specific variations in normal yeast population, how certain breeds might have high yeast counts without causing issues, and that the anatomical site also influences yeast populations. He notes that there's no clear clinical cut-off for relevance; treatment response often helps assess its significance, as excessive yeast might not always correlate with clinical symptoms.

 

14.39 - John asks Ross about the clinical signs indicating an overgrowth of Malassezia.

 

Ross explains that signs like inflamed or greasy skin, particularly in folded areas, ears, neck, or groin, are indicative of a potential Malassezia issue, especially in predisposed breeds (he names some).

 

16.48 - Sue asks Ross about Malassezia as a primary or secondary disease and its relation to underlying issues.

Ross mentions that Malassezia is a commensal yeast and when it causes disease, it's often secondary to an underlying problem, involving immune system imbalances or hypersensitivity responses. Ross confirms that even in breeds prone to Malassezia, like Basset Hounds, there's usually an underlying cause for yeast proliferation. He mentions high Malassezia colonisation in mucosal populations of Basset Hounds, indicating more than just skin folds contributing to the issue.

 

 

Chapter 3: "Fungal Intrigue and Secret Signs: Unravelling Malassezia's Plot"

 

20.33 - John discusses the common misconception regarding skin folds and Malassezia issues in certain dog breeds with Ross. They touch upon the possibility of Malassezia hypersensitivity, its occurrence in certain dogs, and its association with atopic dermatitis.

 

Ross explains that while Malassezia hypersensitivity exists, its clinical presentation might not always correlate with immediate hypersensitivity reactions. He discusses intradermal testing in Bassett Hounds and the presence of IGE reactivity in some dogs, especially those with atopic tendencies.

 

25.19 - Sue asks Ross about primary care veterinary surgeons' preferred methods for diagnosing Malassezia dermatitis. Ross recommends simple techniques like ear swabs, tape strips, and microscopic examination for diagnosing Malassezia in primary care settings.

 

26.21 – John asks about whether this can be transferred between pets and humans.  Ross discusses the potential for Malassezia transfer between pets but emphasises that transferring Malassezia Pachydermatitis from pets to healthy owners is quite unlikely. He mentions instances in neonatal care units where Malassezia-related infections traced back to pet dogs have been observed, emphasising the importance of handwashing in preventing transmission.

 

28.18 - John inquires about treatment recommendations for Malassezia infections. Ross emphasises the accessibility of Malassezia yeasts for topical treatment and discusses the practical challenges in applying topical therapy to dogs with dense hair coats. He highlights the efficacy of 2% miconazole/2% chlorhexidine and 3% chlorhexidine shampoos based on consensus guidelines, alongside systemic treatments like itraconazole and ketoconazole.

 

 

34.29 - Sue asks Ross about the role of steroids in managing chronic Malassezia otitis and skin infections. Ross explains the importance of oral prednisolone for reversing stenosis in the ear canal and discusses the use of steroids in chronic Malassezia dermatitis, particularly in cases with allergic components, thickened skin, and hyperpigmentation.

 

39.44 - Ross provides a summary of the approach to Malassezia otitis externa and skin infections, suggesting a varied approach depending on the severity of the condition. He highlights situations where combining prednisolone with antifungal treatment may be necessary.

 

Sue and John express their gratitude to Ross for his expertise and wealth of information on Malassezia. They acknowledge the complexity of the subject and appreciate the insights shared during the discussion.