impaginato piccolo - Società Italiana di Parassitologia (SoIPa)

Parassitologia 50: 85-88, 2008
Management of Malassezia-related diseases in the dog
A. Peano, M.G. Gallo
Dipartimento Produzioni Animali, Epidemiologia ed Ecologia Università degli Studi di Torino
Abstract. Most cases of Malassezia dermatitis/otitis in the dog are associated with concurrent dermatoses
or systemic diseases and recurrences are not uncommon. Recognition and control of the predisposing factors
are therefore key factors for successful therapy and prevention of recurrent infections. Currently,
Malassezia dermatitis/otitis is managed by the use of antifungal drugs. Systemic therapy is often necessary,
in particular when clinical signs are severe and widespread. Ketoconazole and Itraconazole are the most
commonly used drugs. Topical therapy is an alternative in case of localized lesions and external ear localizations.
Different commercial formulations, available in clinical practice in form of creams, gels, lotions,
sprays and ear drops are often used as adiuvants to systemic therapy. Topicals more frequently used are
represented by imidazolic antifungals, chlorhexydine and lime sulphur. The presentation deals with more
recent advances about the protocols for treatment of Malassezia-related diseases in the dog. New perspectives,
as the use of natural compounds, immunotherapy and inhibitors of yeast adherence factors, are also
discussed.
Key words: Malassezia pachydermatis; treatment; antifungals; dermatitis; otitis
Overgrowth of Malassezia pachydermatis organisms
on canine epidermidis does not appear to be a selfresolving
condition as it is usually secondary to a skin
or systemic disorder. Changes in the cutaneous
microenvironment, such as increased humidity and
changes in lipids and sebum, and failure of topical and
systemic immune mechanisms to protect the host
against the yeast proliferation can lead to pathogenicity
and various disease states with, in some cases, hypersensitivity
reactions to the yeast itself. By causing these
changes, various diseases have been suggested as
underlying causes of Malassezia dermatitis with or
without ear external canal involvement: hypersensitivity
diseases, especially atopic dermatitis, parasite infestations,
keratinization disorders, endocrine diseases,
bacterial infections (Plant et al. 1992; Scott et al. 2001;
Chen et al. 2002; Greene 2007).
Therapeutic approaches therefore rely on the treatment
of yeast infections and management of the underlying
problems. The hypersensitivity nature of this disease in
some patients is emphasized by the response to antifungal
therapy described in dogs with classical clinical
findings and various surface sampling techniques
demonstrating little or no yeast. This leads also to consider
that the diagnosis of Malassezia dermatitis, based
on cytological and cultural examination, ultimately
rests on the response to antiyeast treatment (Scott et al.
2001).
Variations in the in vitro susceptibility to antifungal
drugs have been reported for the different Malassezia
species (Hammer et al. 1999; Velegraki et al. 2004).
Correspondence: Andrea Peano
Dip. Produzioni Animali, Epidemiologia ed Ecologia
Università degli Studi di Torino, Via Leonardo da Vinci 44,
10095 Grugliasco (To), Italy
Tel +39 011 6709001, Fax +39 011 6709000,
e-mail: andrea.peano@unito.it
Most M. pachydermatis strains isolated from humans
or dogs have been found susceptible to the antifungals
amphotericin B, albaconazole, bifonazole, ciclopiroxolamin,
econazole, ketoconazole, itraconazole, clotrimazole,
miconazole, voriconazole, nystatin, pimaricin,
terbinafine (Gupta et al. 2000; Nakamura et al. 2000;
Garau et al. 2003; Cole et al. 2007; Lyskova et al.
2007) while few strains seem to be resistant to fluconazole
(Lyskova et al. 2007) and most strains to flucytosine
(Garau et al. 2003). Ketoconazole seems to be
more active than clotrimazole and miconazole and
equivalent to itraconazole (Cole et al 2007). In a recent
survey some strains isolated from dogs with otitis externa
were considered resistant to clotrimazole and
miconazole, but the interpretation of in-vitro susceptibility/resistance
was not achieved following a NCCLS
guideline (Rougier et al. 2005). Among antiseptics
chlorhexydine has been proved as an antiyeast compound
(Lloyd and Lamport 1999; Lloyd and Lamport
2000; Nebbia et al. 2008). Also miscellaneous topical
agents like selenium sulphide and lime sulphur possess
anti-Malassezia properties (Scott et al. 2001).
Formulations of the commercial products have been
shown to play a role in the final efficacy as they contain
other substances that may, for example, act in synergy
or permit a better in-vivo diffusion of the antifungal
principles (Lloyd et al. 1999; Nebbia et al. 2008).
Studies on alternative therapeutic agents to the commonly
used antimycotic and antiseptic synthetic substances
have demonstrated an in-vitro anti-Malassezia
activity for the essential oil of Melaleuca alternifolia
(Weseler et al. 2002), for β-Thujaplicin, chemical substance
obtained from the trunks/branches or roots of
the conifer Thujopsis dolabrata (Nakano et al. 2005)
and for xanthorrhizol, a bioactive compound isolated
from the edible plant Curcuma xanthorrhiza (Rukayadi
and Hwang 2007). M. pachydermatis-related dermatitis
and otitis are often very difficult to control, with