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Principal Animal Hosts: Dogs, cats, cattle
Clinical Disease in Animals: Dogs - focal alopecia, scaly patches with broken hairs; cats - focal alopecia,
scaling, crusting; cattle - scaling patches of alopecia with gray-white crust; calves - periocular lesions
Probable Mode of Transmission: Direct contact with fomites and infected animals
Skin: Pityriasis (Tinea) Versicolor
MAJ Daniel Schissel, MC, USAIntroduction: Pityriasis versicolor (tinea versicolor) is a chronic, asymptomatic fungal infection caused by
Pityrosporum orbicularis, a normal resident of the skin. The fungus, found worldwide, is seen most commonly
in young adults in temperate zones, and accounts for up to 5% of all reported fungal skin infections. The fine
scales of this lesion are teeming with hyphae and spores that transmit the disease. Factors that predispose
to infection include warm humid climate, genetic predisposition, high plasma cortisol levels (i.e., patients taking
corticosteroids), serious underlying disease or immunocompromise, pregnancy.
Subjective: Symptoms
Asymptomatic to slightly pruritic depigmentation of skin.
Objective: Signs
Using Basic Tools: White, tan, brown, or pink coalescing macules and patches with a fine scale; found most
commonly on the upper torso and neck (or face in children).
Using Advanced Tools: Lab: KOH prep of scales reveals numerous short, straight or ring-shaped hyphae.
Assessment:
Differential Diagnosis
Allergic contact or irritant dermatitis, various tinea, post inflammatory changes (hyper- or hypo-pigmentation),
vitiligo (familial, autoimmune hypopigmentation, with only cosmetic effects). See appropriate sections and
index in this book.
Plan:
Treatment
Primary: Ketoconazole 400 mg po with orange juice to aid in absorption, wait one hour, exercise, leave
sweat on body till the morning, then wash with selenium sulfide suspension. Repeat in one week
Alternative: Fluconazole 200 mg po as above.
Primitive: Apply Propylene glycol 50% in water bid for 2 weeks.
Patient Education
General: Relapse may require weekly washing with selenium sulfide suspension. Repigmentation of the
affected areas takes up to 90 days.
Diet: No alcohol use with oral medications
Prevention and Hygiene: Use antifungal soaps. Wash weekly with selenium sulfide.
Follow-up Actions
Evacuation/Consultation Criteria: Evacuation is not necessary. If lesions do not respond to appropriate
therapy refer patient to dermatologist or to endocrinologist to rule out endocrine disorders.