Malassezia Dermatitis Vet Hospital II Kim Geary Malassezia Dermatitis is a fungal skin infection. It is caused by Malassezia pachydermatis, a “lipophilic, non-lipid-dependent, nonmycelial saprophytic yeast.” (D.V.M Scott, V.M.D. Miller, Jr., and D.V.M. Griffin 363-374). Malassezia is most commonly located in the ear canal, anal sacs, vagina, and rectum. While cats are susceptible to Malassezia infections, it is far more prevalent in dogs. It has been shown that within the Malassezia genus there are “six lipid dependent species and one non-lipid-dependent species.” (D.V.M Scott, V.M.D. Miller, Jr., and D.V.M. Griffin 363-374). While yeast itself is commonly found on the skin, Malassezia can become a serious problem when the skins immune system is weakened enough to allow it [Malassezia] to enter. This can occur with any hereditary or infectious disease, though is most common with bacterial infections, allergies, and seborrhea (Veterinary & Aquatic Services Department, Drs. Foster & Smith).Clinical Signs Malassezia most often begins in summer and/or very humid months, much like allergy season. “Over 70% of the dogs have concurrent dermatoses, especially allergies, keratinization defects, endocrinoptathies, and bacterial pyodermas” (D.V.M Scott, V.M.D. Miller, Jr., and D.V.M. Griffin 363-374). Like many dermatological disorders, the most common clinical sign of a Malassezia infection is an extreme pruritus.
The pruritus may be “partially responsive to corticosteroids and antibiotics (D.V.M. Patterson, and D.V.M. Frank 612-622) and can potentially cause further trauma to the skin (Veterinary & Aquatic Services Department, Drs. Foster & Smith). Other signs area alopecia, and in chronic cases, hyperpigmentation and lichenification (D.V.M Scott, V.M.D. Miller, Jr., and D.V.M. Griffin 363-374). Malassezia dermatitis can be localized or generalized. When generalized the animal will typically have an “offensive, greasy smell and may suffer from oily, scaly skin” (Veterinary & Aquatic Services Department, Drs. Foster & Smith). With localized Malassezia infections the animal may rub its face if localized ...
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The pruritus may be “partially responsive to corticosteroids and antibiotics (D.V.M. Patterson, and D.V.M. Frank 612-622) and can potentially cause further trauma to the skin (Veterinary & Aquatic Services Department, Drs. Foster & Smith). Other signs area alopecia, and in chronic cases, hyperpigmentation and lichenification (D.V.M Scott, V.M.D. Miller, Jr., and D.V.M. Griffin 363-374). Malassezia dermatitis can be localized or generalized. When generalized the animal will typically have an “offensive, greasy smell and may suffer from oily, scaly skin” (Veterinary & Aquatic Services Department, Drs. Foster & Smith). With localized Malassezia infections the animal may rub its face if localized on the muzzle or lick its paws if localized on the toes (Veterinary & Aquatic Services Department, Drs. Foster & Smith). The dogs will more than likely have concurrent dermatoses. It has been found that “about 40% of the dogs with Malassezia dermatitis have concurrent staphylococcal pyoderma” (D.V.M Scott, V.M.D. Miller, Jr., and D.V.M. Griffin 363-374).Diagnosis Because Malassezia dermatitis is so often associated with other skin disorders, it should always be considered in any case involving a pruritic dermatitis and greasy or waxy skin (D.V.M Scott, V.M.D. Miller, Jr., and D.V.M. Griffin 363-374). There are many ways to obtain a sample for microscopic evaluation. A cotton swab, impression smear, skin scrap, and scotch tape sample are all effective ways to obtain a sample. Each of these methods is equally effective, all with their own benefits (D.V.M Scott, V.M.D. Miller, Jr., and D.V.M. Griffin 363-374). After the sample is attained it should then be transferred to a glass slide and heat fixed, with the exception of the tape method. The samples may also be stained using New Methylene Blue in place of heat fixing (D.V.M Scott, V.M.D. Miller, Jr., and D.V.M. Griffin 363-374). A skin biopsy also can be performed, although it is a very invasive option it can provide much more diagnostic information (D.V.M. Brooks). Another way to diagnosis Malassezia is to culture. It is typically easy to culture because it is not lipid dependent and grow best on Sabouraud’s dextrose agar with the exception of the lipid-dependent Malassezia spp. (D.V.M Scott, V.M.D. Miller, Jr., and D.V.M. Griffin 363-374). Care should be taken when diagnosing Malassezia infections solely on finding the yeast as healthy asymptomatic dogs will often have the yeast present on the skin (Veterinary & Aquatic Services Department, Drs. Foster & Smith). Thus the most effective diagnosis is the response to antifungal treatments (D.V.M Scott, V.M.D. Miller, Jr., and D.V.M. Griffin 363-374).Pathophysiology The Malassezia pachydermatis cell is thick walled unipolar budding yeast, ovoid to ellipsoid in shape (D.V.M. Patterson, and D.V.M. Frank 612-622). It is rarely reported in cats, however has been observed in FIV positive cats (D.V.M Scott, V.M.D. Miller, Jr., and D.V.M. Griffin 363-374). Malassezia is believed to have a “symbiotic relationship with commensal staphylococci, wherein the organisms produce mutually beneficial growth factors and microenvironmental alteration that are mutually beneficial” (D.V.M Scott, V.M.D. Miller, Jr., and D.V.M. Griffin 363-374). The dermatitis is thought to be a result of an “inflammatory and/or hypersensitive reactions to yeast products and antigens” because it doesn’t invade subcorneally (D.V.M Scott, V.M.D. Miller, Jr., and D.V.M. Griffin 363-374). Malassezia does have a genetic predisposition. It is most commonly seen in the “West Highland white terrier, Basset hound, American Cocker spaniel, Shih Tzu, English setter, and Dachshund (D.V.M Scott, V.M.D. Miller, Jr., and D.V.M. Griffin 363-374).Treatment/Prognosis For cases with generalized Malassezia dermatitis, shampoos containing miconazole 2%, chlorhexidine 3% or 4%, or a combination of miconazole 2% and chlorhexine 2% are quite effective. Keratolytic degreasing shampoo should precede the previous shampoos if the animal is extremely greasy, waxy, or scaly. Selenium sulfide 1% is also quite effective as it is keratolytic, antiyeast, and degreasing. If the shampoos by themselves aren’t working they can be followed by lime sulfur 2%, acetic acid 2.5%, or enilconazole 0.2% dips. For localized infections antifungal creams, ointments, sprays, or lotions can be used. Topical treatments may also be combined with oral medications. Ketoconazole is the most common, however itraconazole and fluconazole are also effective (D.V.M Scott, V.M.D. Miller, Jr., and D.V.M. Griffin 363-374). Acetic or boric acid can help maintain a normal pH for ear infections (peted). A response to treatment is generally seen within 7 days, but treatment should continue for at least 7 to 10 more days with 4 weeks being the average duration of treatment (D.V.M Scott, V.M.D. Miller, Jr., and D.V.M. Griffin 363-374). While systemic and topical therapy is effective against Malassezia dermatitis, because it is most often associated with concurrent dermatoses, it must be treated as well (D.V.M Scott, V.M.D. Miller, Jr., and D.V.M. Griffin 363-374). Malassezia will typically reoccur especially within those predisposed breeds. While irritating to pet and owner alike, Malassezia is a nonfatal and treatable infection. Works CitedD.V.M Scott, Danny W., William H. V.M.D. Miller, Jr., and Craig E. D.V.M. Griffin. "Fungal Skin Diseases." Muller and Kirk's Small Animal Dermatology. 6th. Philadelphia: W.B. Saunders Company, 2001. Print Veterinary & Aquatic Services Department, Drs. Foster & Smith, . "Malassezia (Yeast) Infections in Dogs." peteducation.com. Foster & Smith, Inc., 2010. Web. 29 Mar 2010. D.V.M. Brooks, Wendy C. "Malassezia Dermatitis (Yeast Infection of the Skin)." The Pet Health Library. Veterinary Information Network, Inc., 09/10/2001. Web. 29 Mar 2010. <http://www.veterinarypartner.com>. D.V.M. Patterson, Adam P., and Linda A. D.V.M. Frank. "How to diagnose and treat Malassezia dermatitis in dogs." Veterinary Medicine (2002): 612-622. Web. 29 Mar 2010.
