Felis ISSN 2398-2950

Skin: dermatophytosis

Synonym(s): Ringworm

Contributor(s): Rosanna Marsella, Ian Mason, David Scarff, David Godfrey

Introduction

Cause: infection with Microsporum canis most common Microsporum canis .
Direct and indirect transmission.
Common zoonosis .
Often self-limiting.
Signs: variable.
Treatment: responds to treatment with antifungal agents Therapeutics: non-bacterial infection.
Print off the owner factsheet on Ringworm Ringworm to give to your client.

Microsporum canis is the most common cause Microsporum canis .
Trichophyton mentagrophytes Trichophyton spp.
Microsporum gypseum Microsporum gypseum.
Other dermatophytes are rare in the cat.
M. canis: source is usually infected cat.
T. mentagrophytes: source is rodents or their environment.
M. gypseum: inhabits rich soil; exposure occurs during digging in contaminated areas.

Transmitted by contact with infected hair and scale, fungal elements in environment or on fomites.
Mechanical disruption of stratum corneum facilitates infection.
Fungal hyphae invade hair shaft and migrate downwards; they require actively growing hair to survive.
Host immune response determines clinical signs; often self-limiting in healthy cats. However, chronic infections are common in long-haired cats.

Arthrospores germinate within 6 hours of adherence to keratinocytes.
Skin microtrauma is necessary for infection.
Grooming eliminates arthrospores from skin.
Fungal growth in hair → keratinolytic enzymes → penetration of cuticle and hair shaft.
At keratogenous zone, fungus either reaches equilibrium with keratin production or is expelled.
When hair enters telogen phase or inflammatory response mounted → spontaneous resolution.
Toxins produced in stratum corneum → cutaneous inflammation.
Deeper penetration of keratin surface of epidermis → furunculosis → scarring.
Dermatophytic pseudomycetoma in Persian cats - sub-cutaneous nodules.