A three year survey of dermatophytoses in Belgium

Objectives
Dermatophytosis refers to superficial fungal infections of keratinized tissues caused by keratinophilic dermatophytes. They are the most common cause of superficial fungal infections worldwide. Epidemiological studies regarding dermatophyte infections have been conducted in several countries and differences in the incidence and in etiological agents have been reported for different geographical areas. That is why national surveillance of circulating strains causing dermatophytosis is crucial. The Belgian National Reference Center (NRC) for Mycoses conducted a survey on dermatophytes strains circulating from 2012 to 2014. The present study was performed to assess the profile of dermatophytosis and to identify the species involved.

Methods
The Belgian NRC for Mycosis collected 9138 strains between January 2012 and December 2014. The isolates were cultured from patients clinically suspected for fungal infections of skin, hair and nails. Isolates were sent by Belgian laboratories to the two labs of the Belgian NRC (UZ Leuven and CHU of Liège) in order to identify the fungus or to confirm the identification. All isolates cultured from patients of UZ Leuven and CHU of Liège were also included. Fungal identification was performed by microscopy after subculture and in case of doubtful identifications by ITS sequencing.
Results
.Among the 9138 samples (results of UZ Leuven and CHU of Liège combined), 3587 were identified as dermatophytes. Trichophyton. rubrum (T. rubrum) was the most prevalent species accounting for 56,17% (n=2015) of the infections from all sources, followed by T. mentagrophytes complex (21,83%, n=783). The other main etiological agents of dermatophytosis recorded in this study in descending order of prevalence were M. audouinii (n=303), M. canis (n=120), T. violaceum (n=112), T. tonsurans (n= 95), T. soudanense (n=66), M. praecox (n=59), E. floccosum (n=14) Our data reveal the predominance of anthropophilic species causing tinea capitis especially M. audouinii responsible for 36,49% (n=163/448) of hair/scalp infection. Trichophyton violaceum rarely observed in our country is frequently found as 12,8% (n=57) of the reported cases of tinea capitis are due to this species. The retrospective evaluation of data collected also shows that zoophilic strains as M. canis well represented in the past epidemiology of tinea capitis, is decreasing in frequency accounting for only 7,2% (n=32) of clinical cases. Finally, our data confirm the high prevalence of T. rubrum commonly observed in Europe as causal agent of onychomycosis (70,9%, n=1603) followed by T. mentagrophytes complex (20,9%, n=455). T. rubrum and T. mentagrophytes complex are also responsible for the majority of skin infections as they represent respectively 40% (n=386) and 24,75% (n=239) of skin dermatophytosis during the study period.
Conclusions
The present work has provided recent data on the prevalence of several dermatophytes species circulating in Belgium. Such data is critical for the establishment of therapeutic strategies and measures for prevention and control of dermatophytes infections. Our study confirms the predominance of T. rubrum followed by T. mentagrophytes in the Belgian population but also highlights the emergence of new anthropophilic species such as M. audouinii and T. violaceum as causative agents of tinea capitis in children in relation with African immigration.