Trichophyton equinum
Trichophyton equinum is a species strongly associated with horses. It is generally reported as the most common cause of dermatophytosis in horses worldwide and occasionally causes outbreaks in horse farms (English 1961; Connole and Pascoe 1984; Pereira et al.
2006). The infections prevail in young animals, and additional risk factors for dermatophytosis include poor grooming practice, moist conditions, and a high number of animals in the herd (Ahdy et al. 2016). Available data from Italy, Jordan, and Egypt found prevalence of dermatophytosis in horses 9, 18, and 16.8%, respectively, and T. equinum represented 66.7, 24 and 58.4% of all isolated dermatophytes (Moretti et al. 1998; Al-Ani et al. 2002; Ahdy et al. 2016). Similarly, the studies on horses with skin lesion from Egypt and Nigeria reported T. equinum as a main causal agent of dermatophytosis that was confirmed in 49.2 and 44% culturepositive cases, respectively (Mahmoud 1995; Nweze 2011). Exceptionally, other species were found with higher frequencies in horses such as M. canis (Al-Ani et al. 2002) and T. verrucosum (Maurice et al. 2016; Balogun et al. 2017). The latter species is usually found when horses are pastured with cattle (Weiss et al. 1984).Occupational infections in breeders, riders and veterinarians are relatively rare (less than 30 cases reported in the literature) and usually manifest as tinea corporis and tinea capitis, exceptionally as onychomycosis (Veraldi et al. 2018).
The differentiation of T. equinum from closely related anthropophilic T. tonsurans is possible based on ecological preferences, nutritional requirements, and mating behavior (Woodgyer 2004; Summerbell et al. 2007), while distinguishing based on DNA sequence data may be problematic (de Hoog et al. 2017).
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