Les dermatophytoses équines : des dermatoses toujours d'actualité

Abstract

Dermatophytosis (ringworm, tinea) is a skin disease particularly common in horses. It is highly contagious, which explains the frequent outbreaks wherever horses are housed together (stud farms, riding schools, liveries…). Recent molecular analyses of dermatophytes have raised questions on the validity of certain dermatophyte species or varieties previously described as pathogenic for horses based on their phenotypic characteristics. Trichophyton equinum is responsible for most of dermatophytosis cases in horses. This species is very host-specific, and only exceptionally affects other animal species or man. The development of Trichophyton equinum in the skin’s corneum stratum and hairs produces a dry form of ringworm, with moderate inflammation, alopecia, erythema, scaling and generally no pruritus. Clinical signs are highly variable and the risk of confusion with other dermatoses is not negligible. The diagnosis is based on anamnesis, accurate observation of the skin lesions, and the essential laboratory tests (direct examination and fungal culture). Clinical management should combine topical and systemic antifungal drugs. Environmental decontamination is also required, taking into account the spores’ capacity for prolonged survival. Although vaccination is a very promising preventive measure, no vaccine against equine dermatophytoses is currently licensed for use in France.