Malasseziasis in Dog: a Case Report in Nepal

Case History:

Wesley, a 7-year-old maleGermon Shephord , was presented because of a nine-month history of hair loss and thickened, greasy skin. The dog was moderately pruritic, but the owner could not recall if pruritus had preceded or followed the appearance of the skin lesions. The dog seemed healthy otherwise. A vinegar and water solution had been used topically as well as selenium sulfide shampoo with minimal improvement. Prednisone was dispensed six months before presentation but did not seem to help. The owner had tried different brands of dog food but with no improvement.

Physical examination:

Physical examination revealed severe alopecia, hyperpigmentation, and lichenification of the ventral chest and. The legs and ventral neck were also affected. The hair was greasy and epilated easily. The outer ear canals were thickened and contained a brown discharge. The peripheral lymph nodes were moderately enlarged. Wesley's abdomen seemed distended, and the liver was palpably enlarged but non-painful. His testes were symmetrical but small and soft.

Differential diagnoses

Lichenification can be seen with many chronic infectious (bacterial, demodectic mange, fungal), allergic (fleas, food, atopy), or seborrheic skin disorders, but lichenification of the ventral neck, chest, and axillary areas is particularly characteristic of yeast dermatitis (Malassezia pachydermatitis). Lichenification is also seen in West Highland white terriers affected with epidermal dysplasia, but this was less likely in Wesley's case since epidermal dysplasia is a heritable keratinization defect in which signs usually begin between 6 and 12 months of age.

Because of the physical examination findings of abdominal distention, hepatomegaly, and small testicles, we suspected that an underlying endocrine disease (hyperadrenocorticism, hypothyroidism) may also be present.

Diagnostic tests

Cytologic examination of skin imprints showed many yeast, as well as many cocci. Skin scrapings were negative for mites. Cytologic examination of otic discharge revealed many bacteria (rods and cocci) as well as yeast. Bacterial culture of the ears grew Staphylococcus aureus and B-hemolytic Streptococcus, Corynebacterium, and Malassezia species. All bacteria were sensitive to several antibiotics, including enrofloxacin and cephalothin, but were resistant to gentamicin.

The results of a complete blood count showed a mild normocytic, normochromic anemia (hematocrit = 32%; normal = 35% to 57%) and a slightly elevated total white blood cell count (14,000/l; normal = 5,100 to 13,000/l) with a mild left shift (bands = 700/pl; normal = 0 to 450/l), The serum chemistry profile results revealed hyperproteinemia (8.5 g/dl; normal = 5.4 to 7.5 g/dl) presumed to be due to elevated globulin concentration (albumin concentration = 3.2 g/dl; normal = 2.7 to 4.4 g/dl). Urinalysis and ACIH stimulation test results were normal. The thyroid-stimulating hormone concentration was 0.8 ng/ml (normal -0 to 0.5 ng/ml), and free serum total thyroxine by equilibrium dialysis was 5 pmol/L (normal = 10 to 45 pmol/L). We diagnosed yeast and bacterial dermatitis and otitis secondary to hypothyroidism.

Discussion

Malassezia pachydermatis is a normal inhabitant of canine skin, especially in the areas of the external ear canals, feet, lips, and perineum.1 A change in the skin environment, such as increased sebum or moisture, or an alteration of the epidermal defense system predisposes animals to yeast overgrowth. The most common underlying diseases associated with yeast dermatitis include allergies (flea, food, or atopy), endocrinopathies (hypothyroidism or hyperadrenocorticism), or keratinization disorders such as primary seborrhea or epidermal dysplasia. Long-term exogenous corticosteroid administration or long-term antibiotic therapy may also predispose dogs to yeast or bacterial infections.2-4

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Clinical signs of Malassezia dermatitis in dogs include alopecic, lichenified, erythematous skin with adherent yellow scales. Most affected animals are severely pruritic and often malodorous. Areas most commonly affected include the ventral neck, auxiliary and inguinal areas, and flexural surfaces of the hocks and elbows.2-4 With chronic infections, the skin becomes hyperpigmented3 and elephant-like. Pedal malasseziasis can present as red, moist interdigital areas, often with a concurrent bacterial infection. Brown staining of the proximal toenails has been associated with yeast paronychia.3 Breeds predisposed to malasseziasis include West Highland white terriers, cocker and springer spaniels, basset hounds, and German shepherds.2-4 Some animals may have a yeast hypersensitivity and severe pruritus with relatively few organisms.3,5

It can be diagnose Malassezia dermatitis by identifying characteristic clinical signs and cytologically examining the skin. The cytology can be performed in several ways. You could obtain a skin impression by pressing a clean, dry slide onto an affected area, and then heat-fix and stain (Diff-Quik [Dade Behring], Gram's, or Wright's stain) the slide. Alternatively, obtain scale by gently scraping a dulled scalpel blade over affected skin, and smear the debris onto a clean, dry slide that is then heat-fixed and stained. Or firmly apply clear acetate tape onto several areas of affected skin to obtain debris. Then place the tape sticky-side down onto a slide on top of a drop of new methylene blue.

View slides under 40X or 100X magnification. More than one or two yeast organisms/hpf is clinically relevant, especially in conjunction with clinical signs. Obtaining a skin biopsy sample is usually not necessary or particularly helpful, but histopathologic findings include marked parakeratotic hyperkeratosis and spongiosis with Iymphohistiocytic inflammation.2-4

Treatment for Malassezia dermatitis includes topical or systemic therapy. Topical therapy alone may be sufficient in patients with mild localized disease but may not adequately treat a generalized infection. Topical therapies include degreasing shampoos containing benzoyl peroxide, tar, or selenium sulfide and antimicrobial shampoos such as chlorhexidine (at concentrations greater than 2%), miconazole nitrate, or ketoconazole. Advise clients to shampoo the animal every two or three days initially and then decrease the frequency as the condition improves. The lather should be left on the skin for at least 10 minutes before rinsing. Other topical therapeutic options include 2% lime sulfur dip (applied after a degreasing shampoo) and leave-on 2% chlorhexidine or miconazole conditioners. In situations in which cost is a concern, you can suggest a 50:50 solution of white vinegar and water as a whole body rinse after bathing or as a daily spray on affected areas.

In cases of generalized Malassezia dermatitis, topical therapy is often used in combination with a systemic anti-fungal medication such as ketoconazole (5 to 10 mg/kg orally once or twice a day given with food). Because of the potential for hepatotoxicity, measure serum liver enzyme activities periodically in animals receiving long-term (more than three weeks) ketoconazole therapy. Itraconazole (5 to 10 mg/kg orally once a day) and fluconazole (5 mg/kg orally once a day) can also be used but are considerably more expensive.3 Oral antifungal therapy is continued for three to four weeks. To decrease medication cost, some clinicians prescribe 5 to 10 mg/kg of ketoconazole given once a day for the first 10 days and then every other day for 10 days.3 Griseofulvin is not effective against Malassezia species.Of equal importance in diagnosing and treating yeast dermatitis is identifying and addressing the underlying cause. Depending on the patient's history, signalment, and physical examination findings, other diagnostic procedures could include a hypoallergenic diet trial, tests for flea or inhalant allergies, or blood tests for endocrine or metabolic diseases.

This case was unusual because skin disease in West Highland white terriers is most commonly associated with allergies, and hypothyroidism is uncommon in this breed.

Conclusion And Recommendation

Dog was treated topically for yeast dermatitis with benzoyl peroxide shampoo (twice a week for three weeks, then once weekly) followed by a leave-on 2% chlorhexidine conditioner. He also received systemic anti-fungal medication (10 mg/kg ketoconazole orally once a day for four weeks). For the deep bacterial pyodemla, cephalexin was dispensed (22 mg/kg orally t.i.d. for eight weeks). The bacterial otitis was initially treated twice a day with a topical combination gentamicin sulfate-betamethasone valerate-clotrimazole ointment; we changed this to a topical combination enrofloxacin-dexamethasone-ear cleaner mixture (6 mI enrofloxacin, 12 mg dexamethasone, and 24 mI DermaPet Ear/Skin Cleanser [DermaPet]) when we obtained the culture results. We also prescribed levothyroxine sodium (0.022 mg/kg orally b.i.d.) and recommended a post-pill thyroid hormone measurement after three weeks ensure adequate dosage.

At the 30-day recheck visit, Wesley's lichenification was 500/0 improved. He had minimal pruritus and was starting to regrow hair on his legs. The owner reported that the dog's attitude and activity level had improved markedly. Cytologic examination of the skin showed few yeast and bacteria. Serum liver enzyme activities revealed a moderately increased alanine transaminase (331 U/L; normal = 12 to 108 U/L) suggestive of ketoconazole- induced hepatic injury. The ketoconazole dose was decreased to 10 mg/kg every other day for two weeks to resolve the residual yeast infection, and then the drug was discontinued. Five months after initial presentation, the owner reported that Wesley was doing well with no recurrence of lichenification, pruritus, or hair loss.

REFERENCES

1. Bond, R. et al.: Population sizes and frequency of Malassezia pachydermatis at skin and mucosal sites on healthy dogs. J. Small Anim. Pract. 36:147-150; 1995.

2. Scott, D. W. et al.: Fungal skin diseases. Muller & Kirk's Small Animal Dermatology, 5th Ed. W.B. Saunders, Philadelphia, Pa., 1995; pp 329-391.

3. Muse, R.: Malassezia dermatitis. Kirk's Current Veterinary Therapy XIII Small Animal Practice (J.D. Bonagura, ed.). W.B. Saunders, Philadelphia, Pa., 2000; pp 574-577.

4. Reberg Bruner, S.; Blakemore, J.C.: Malassezia dermatitis in dogs. Vet. Med. 94 (7):613-622; 1999.

5. Morris, D.O.; Rosser, E.J.: Immunologic aspects of Malassezia dermatitis in patients with canine atopic dermatitis. Proc. ACVD/AAVD), ACVD/AAVD, Santa Fe, N.M., 1995; pp 16-17.

6. Mason, K.V.: Cutaneous Malassezia. Current Veterinary Dermatology, 1st Ed. (C.E. Griffin et al., eds.). Mosby-Year Book, St. Louis, Mo., 1993; pp 44-48.

7. A dog with elephant-like skin

Kimberly Lower, DVM; Linda Medleau, DVM, MS, Dipl. ACVD; and Keith Hnilica, DVM, MS, Dipl. ACVD 8909 Iverleigh Court Potomac, Maryland 20854, www.dermapet.com/articles/art-20.html Dermapet Articles of interest 16dec 2007

投稿者 Max 時刻: 21:15