RINGWORM
• Dermatophytes are filamentous fungi with a high affinity for keratin, capable of causing superficial cutaneous infections in human and animal hosts. 1,2 • Over forty species from three genera ( Microsporum, Trichophyton and Epidermophyton ) are identified, and more than twenty species have been isolated from companion animals. 3,4 • Dermatophytosis (also known as ringworm) is a common superficial fungal infection of dogs and cats, most commonly involving Microsporum and Trichophyton species. 4 Microsporum canis is the species most commonly implicated in zoonotic dermatophyte disease of humans, however human dermatophytosis is primarily non-zoonotic, associated with anthropophilic dermatophytes (e.g. Trichophyton rubrum, T. mentagrophytes ) and geophilic dermatophytes (e.g. Nannizzia gypsea ; formerly Microsporum gypseum ) acquired via human-to-human contact or contact with soil respectively.
ACAZAP RECOMMENDATIONS
• If a cat or dog is diagnosed with dermatophytosis, all in-contact animals and household human contacts should ideally be screened for dermatophytes using fungal culture. Both asymptomatic and symptomatic individuals and animals should be treated to prevent the cycle of transmission continuing. • Topical therapy can decrease the zoonotic risk associated with dermatophytosis by disinfecting the hair coat and minimising environmental contamination. Twice weekly application of a fungicidal shampoo containing miconazole is recommended for the treatment of generalised dermatophytosis in dogs and cats. 5 Careful clipping of hair around localised lesions is recommended, however full coat clipping may contribute to further spread of skin lesions associated with skin microtrauma and increased environmental contamination if not carefully performed. 5 • Topical therapy may be combined with systemic antifungal treatment, particularly for recurrent and/or generalised infections, in immunocompromised animals, or when managing outbreaks in large facilities. Although there are no registered systemic antifungal products for dogs and cats in Australia, a number have been reported effective in these species including itraconazole, terbinafine and griseofulvin, although the latter may be associated with a greater potential for adverse events. 5 • Animals with chronic M. canis infections should be evaluated for underlying diseases.
• Vacuuming and mechanical cleaning of the environment is essential to reduce the presence of infective material. To minimise the potential for redistribution of infective material, vacuums incorporating a HEPA exhaust filter are recommended. • In a veterinary hospital or shelter setting, additional environmental decontamination using a disinfectant with anti- fungal efficacy (e.g. 1:10 dilution of household bleach) is vital to minimise fomite carriage and potential re-infection. Surfaces should be thoroughly cleaned prior to disinfection. • Potential fomites should be discarded where possible or appropriately cleaned. Bedding and blankets should be washed daily in water and bleach. • All heating and cooling vents should be vacuumed and disinfected. All non-porous surfaces (floors, surfaces, counter tops) should be thoroughly cleaned. • Education of veterinary and animal handling staff about the risks of zoonotic infection is essential. Gloves should be routinely worn when examining animals with skin lesions. • In the veterinary clinic, infected animals should be isolated and gloves and protective clothing should be worn when handling infected animals and bedding. • If a human patient is diagnosed with a dermatophyte infection, examination and testing of household pets is recommended to determine their role, if any, in the infection. This is particularly important in the case of recurrent human infections.
CONTENTS
67 Companion Animal Zoonoses Guidelines
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