3.2.4. The controversy and ‘Dark Years’: 1940 to 1960 1940-1960 are known as the ‘Dark Years’ and spanned a period of more controversy. The hard won progress in the field was forgotten as a consequence of the Second World War and the overwhelming effect of cortisone treatment becoming available in the late 1940s, to which human seborrhoeic dermatitis responded. The role of Malassezia yeasts in the disease was thus forgotten. 1970 The systematics were rectified when Sloff in Lodder’s ‘The Yeasts, a taxonomic study’ assigned all Pityrosporum that grew on media without lipid enrichment as single species of P pachydermatis.[53] 1984, The third edition of ‘The Yeasts, a Taxonomic Study’ (Yarrow and Ahearn) referred to the new genus Malassezia and confirmed that one species grew without lipid enrichment.[54] [55]. This was later officially added into the taxonomical order.[56] 1990 A new species, Malassezia sympodialis was described[19] and by 1996 four new species were added to the genus.[20] This species was later isolated from a cat by Bond et al. in 1996.[57] 3.2.5 Modern Technology Currently there are 17 different species of Malassezia.[35, 58] The genus continues to expand and this is likely to continue as the classical ‘bottom-up’ microbiological approaches merge with organism-level genomics and community or ‘systems--level meta-genomics. 3.3 Malassezia yeasts in animals 3.3.1. Canine ear and skin disease: the first reports (1951 to 1999).
administrated once daily for 3 weeks [425], there is insufficient evidence to comment specifically on the efficacy of the various doses used (5 or 10 mg/kg, once or twice daily). Reports of improved efficacy with KTZ at doses of 10 mg/kg twice daily [390](Mason and Stewart 1993) do not appear to have been subjected to critical comparative trials. Adverse reactions are regularly reported with the use of ketoconazole in dogs; a retrospective study of 632 dogs that received a median daily dose of 10 mg/kg reported adverse effects in 14.6%, including primarily vomiting (7.1%), anorexia (4.9%), lethargy (1.9%) and diarrhoea (1.1%).[426] Adverse effects were significantly more frequent in dogs receiving concurrent ivermectin or ciclosporin.
Table 4. Clinical trials of oral ketoconazole in the treatment of canine Malassezia dermatitis in dogs. Study Design Dose used Clinical outcome Adverse effects Comment LoE Bensignor 2001[425] RCT-UB (10 dogs per group) 5 OR 10 mg/kg once 7/20 complete response, rest partial In 10 mg/kg vomiting [n=2], anorexia [n=1], apathy [n=1] Small group sizes; two KTZ doses compared 2 Rosales et al. 2005 [148] RCT-B (7 dogs received KTZ) 5-10 mg/kg twice daily 4/7 >50 % clinical improvement Nil group sizes and concurrent cefalexin therapy limits interpretation. Compared with terbinafine. 2 Bensignor 2006[424] RCT-B (10 dogs received KTZ) 10 mg/kg once 4/10 complete response, 6/10 partial Nil Small group sizes; compared to pulse ITZ 2 Bensignor et al. 2012[421] RCT-B (10 dogs) 10 mg/kg once daily 83% improvement at 6 wks Not specified Abstract publication only; compared to shampoo alone or combined with KTZ 2 Sickafoose et al. 2010[384] RCT-B (12 dogs received KTZ + cefalexin) 5-10 mg/kg once daily 7/12 >50 % clinical improvement 6/12 dogs: transient anorexia [n=2], vomiting [n=3], vomiting and soft stool [n=1] Concurrent cefalexin therapy limits interpretation. 2 RCT-B, randomised controlled – blinded; RCT-UB, randomised controlled – unblinded . trial:
Table 7. Clinical trials of a 2% miconazole / 2% chlorhexidine and 3% chlorhexidine shampoos in the treatment of canine Malassezia dermatitis. Study Product Design Frequency Clinical outcome Adverse effects Comment LoE Bond et al. 1995[147] 2% miconazole / 2% chlorhexidine RCT-B (16 basset hounds received MC-CH) Every third day 15/16 ‘marked improvement’ Nil Compared to 0.25% selenium sulphide shampoo 1 Maynard et al. 2011[274] 2% miconazole / 2% chlorhexidine RCT-B (32 dogs received MC-CH) Twice weekly Good (≥50%) response in 91% of dogs Nil Compared to 3% Chlorhexidine shampoo 1 Bensignor et al. 2012[421] 2% miconazole / 2% chlorhexidine RCT-B (10 dogs) weekly 85% improvement at 6 wks NR Abstract publication only 2 Maynard et al. 2011 3% chlorhexidine RCT-B (22 dogs received CH) Thrice weekly for 2 weeks, then twice weekly for two weeks, then weekly if needed Good (≥50%) response in 86% of dogs Transient pododermatitis [n=1], increased pruritus [n=2], exfoliation [n=2] Compared to 2% miconazole / 2% chlorhexidine 1
Inflamed Linear epidermal nevis. Parakeratosis and mixed inflammation on a epidermal papillomatous hyperkeratosis Treatment reduce inflammation and irritation and keratotic epidermal nevis becomes less inflamed. Acanthosis nigricans of Dachshunds Mild to moderate orthokeratosis, focal parakeratosis. Heavy pigmentation in basal cell layer. Irregular epidermal hyperplasia and mixed perivascular or interstitial dermal inflammation. Differentiate primary geno-dermatosis from allergic disease with frictional intertrigo. Assess response to antimicrobial treatment. Hyperplasic dermatitis of West Highland terriers Parakeratotic scales / crusts in mounds, often with yeasts, severe spongiosis and irregular hyperplastic budding, mixed superficial perivascular or interstitial dermal inflammation Breed-specific hyperplastic reaction to yeast. Complete response to antimicrobial treatment in some cases but recurs if predisposing cause not eliminated. Difficult to differentiate from allergic aetiology. Facial dermatitis in Persian and Himalayan cats Acanthosis and spongiosis of epidermis and infundibulae. Parakeratosis and marked scale / crust. Sparse apoptosis Some cases temporarily benefit from antimicrobial therapy.