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82 There is no age or sex predilection, but Malassezia dermatitis or otitis are more often diagnosed in dogs between 1 to 3 years of age. Many breeds seem to be predisposed to Malassezia dermatitis: West Highland White Terrier, Basset Hound, Dachshund, Cocker Spaniel, Poodle, German Shepherd, Collies, Shetland, Jack Russell Terrier, Silky Terrier, Australian Terrier, Springer Spaniel, Newfoundland and Shar Pei. Malassezia dermatitis is often recognized during warm period at the time at which allergic dermatites are generally diagnosed. Malassezia overgrowth or dermatitis is not demonstrated to be contagious for companion animals or man (Morris DO, 2005). In certain breeds, for example Shar Pei and Newfoundland, clinical signs may be particularly severe and epidermal dysplasia in WHWT might be an inflammatory or hypersensitivity reaction to the Malassezia infection or a result of excessive self-trauma, rather than a congenital keratinization disorder. Pruritus is always present but its severity is related to the importance of predisposing factors. Diffuse, regional or localized alopecia, lichenification, hyperpigmentation, erythema, erythematous macules, excessive scaling, and oily skin and hair are the clinical features of canine Malassezia dermatitis. The classical areas involved are neck, axillae, abdomen, pinnae and external ear canal, lips, and peri-anal area. Dogs with generalized lesions have a rancid odour. In allergic cats multifocal alopecia, erythema, crusting and greasy adherent brownish scales are signs of Malassezia overgrowth (Toma S et al., 2006). The distribution is depending from the concurrent diseases, but face, ventral neck, pinnae and ear canal, chin, interdigital and claw fold skin are the most common site of infection. Especially in Devon Rex cats, high number of yeasts in cytology is associated with an abundant brown, greasy material in this natural intertrigo area (Colombo S et al., 2007). Malassezia dermatitis is suspected upon clinical evidence and diagnostic methods used to identify overgrowth of Malassezia organisms. The response to treatment with specific antifungal therapy is considered the best tool for a definitive diagnosis. Cytological examination allows to rapidly observe yeasts and to “quantify” their number. Many techniques are available to obtain material from the skin: 1) direct impression smear; 2) acetate tape (Scotch test); 3) scrape smear; and 4) swab smear. Impression smear and Scotch test seem to be the best techniques if the skin surface is flat or greasy, whereas swab smears should be more useful for cytological examination of the external ear canal. Heat-fixing does not seem to increase numbers of Malassezia on cytology of ear swab samples for cytologic evaluation, and a 1-step dip in the blue reagent alone as a rapid method of staining samples from canine ear canals has been proposed (10). Slides or acetate tape may be stained with Diff-Quick or other rapid methods, May Grünwald-Giemsa, Giemsa or new methylene blue. Microscopic examination with an oil immersion lens (100X) reveals free or adhered to keratinocytes yeasts appearing as oval or elongated cells of 3 to 5 µm in diameter, with a typical single polar bud- S. Nardoni et al. -Veterinary malasseziosis ding. The minimum number of yeasts that indicates the possibility of a true Malassezia dermatitis is not really known. Variations between breeds and body sites have to be considered. Several criteria has been proposed to establish Malassezia overgrowth; as a general guide, 1- 2 organisms per field (100X) in several fields in the presence of typical clinical signs are suggestive of Malassezia dermatitis. Methods to sample Malassezia from the skin for culturing are cotton swabs, acetate tapes, detergent scrubs and contact plates. Appropriate media for the growth of all Malassezia species are mDixon agar and modified Leeming and Notman agar, while selective medium for dermatophytes allows the growth of M.pachydermatis only. As the yeast is a normal component of the cutaneous flora of the dog, by itself a positive culturing has no or little value. However, as for all opportunistic agents, the number of colonies is perhaps an indication (this is comparable to the number of yeasts demonstrated by cytological examination). Dermohistopathology may sometimes show the yeasts on the surface of the epidermis and occasionally in the infundibula, particularly in PAS stained sections (although they are occasionally visible on HE stained sections). However, if they are not seen on biopsy, this does not exclude their presence. False negative results could be caused by the sampling of a non-infected area, removal of the stratum corneum during processing, etc. Cutaneous histopathology is a less sensitive technique than cytology. In contrast, the finding of Malassezia inside hair follicles could indicate a real pathogenicity. The common findings in biopsies from dogs with Malassezia dermatitis, include: orthokeratotic hyperkeratosis with prominent foyers of parakeratosis; spongiosis with irregular ridges; lymphocytic exocytosis of the epidermis; focal accumulation of neutrophils; subepidermal linear alignment of mast cells and moderate superficial perivascular to interstitial dermal inflammation with lymphocyte exocitosis. Clinical signs of Malassezia dermatitis are variable and may mimic many dermatoses, then differential diagnosis includes many pruritic dermatoses characterized by erythema, hyperpigmentation and seborrheoa together with all underlying dermatological diseases of the yeasts overgrowth. References Cafarchia C , Gallo S., Capelli G:, Otranto D., 2005 Occurrence and population size of Malassezia spp. in the external ear canal of dogs and cats both healthy and with otitis. Mycopathologia Sep;160(2):143-9. Chen T, Hill PB 2005 The biology of Malassezia organisms and their ability to induce immune response and skin disease Vet. Dermatol. 16, 4-26. Colombo S, Nardoni S, Cornegliani L, , Mancianti F Prevalence of Malassezia spp. yeasts in feline nail folds: a cytological and mycological study. Vet Derm 2007, 18, 278-283 Nardoni S ,Mancianti F.,Corazza M., Rum A: 2004 Occurrence of Malassezia species in healthy and dermatologically diseased dogs. Mycopathologia May;157(4):383-8. Nardoni S, Dini M, Taccini F., Mancianti F. 2007 Occurrence, dis-
tribution and population size of Malassezia pachydermatis on skin and mucosae of atopic dogs. Vet Microbiol. May 16;122(1-2):172-7. Morris DO 2005 Malassezia pachydermatis carriage in dog owners. Emerg Infect Dis Jan;11(1):83-8. Prado MR, Brilhante RS, Cordeiro RA, Monteiro AJ, Sidrim JJ, Rocha MF. 2008 ; Frequency of yeasts and dermatophytes from S. Nardoni et al. - Veterinary malasseziosis 83 healthy and diseased dogs. J Vet Diagn Invest. 20(2):197-202 Scott DW, Miller WH, Griffin CE “Muller&Kirk’s” Small Animal Dermatology. WB Saunders 2001, pp363-374. Toma S, Cornegliani L, Persico P, Noli C 2006 Comparison of 4 fixation and staining methods for the cytologic evaluation of ear canals with clinical evidence of ceruminous otitis externa. Vet Clin Pathol Jun; 35(2):194-8.
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PARASSITOLOGIA A publication of the
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P A R A SSIT O L O GIA Founded in 1
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The individual authors take respons
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Parassitologia 50, 2008 RICORDO DEL
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Parassitologia 50: 9-16, 2008 The c
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eceptor subunits move closer togeth
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Chemokines have several functions a
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tion of the brain. Nature 421:744-8
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Parassitologia 50: 17-24, 2008 Epid
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adic or imported cases have been ob
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other EU countries, yet the impact
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Fasciola hepatica. II: La fasciolos
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Parassitologia 50: 25-29, 2008 Arte
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Ferry along the Potomac River. The
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for each of these chemical entities
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Page 40 and 41: 36 Many children with congenital to
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Page 46 and 47: 42 References Ades AE, Gilbert R, T
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Page 64 and 65: 60 (Kijlstra et al., 2006). Regardi
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Page 70 and 71: 66 C. Cafarchia, D. Otranto - Malas
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Page 78 and 79: 74 R. Galuppi, M.P. Tampieri - Mala
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134 approach and SAR studies. DDcl
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136 Program financed by ANTIMAL. S.
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138 A. della Torre et al. - Researc
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140 A. della Torre et al. - Researc
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E. Schwarzer et al. - Hemozoin and
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148 geographic distribution in sub-
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150 K.E., Beldjord, C., Nagel, R.L.
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