Trichophyton erinacei: An Emerging Pathogen Introduced into New Regions Along with Hedgehogs
Smith and Marples (1964) gave a status of variety T. mentagrophytes var. erinacei to a “hedgehog fungus” based on morphological and physiological differences from other varieties of T.
mentagrophytes. It was elevated to a species level by Quaife (1966), and the species rank was supported by phylogeny (Graser et al. 1999b) (Fig. 3.3).European hedgehog (Erinaceus europaeus) was first reported as a host along with infection of humans who were in contact with animals (Smith and Marples 1964). The four-toed hedgehog (Atelerix albiventris) is another host of T. erinacei as verified by sequence data and mating experiments (Takahashi et al. 2002). Trichophyton erinacei has been recorded also from dogs (Pierard-Franchimont et al. 2008; Kurtdede et al. 2014), wood mice (Apodemus sylvaticus) (English 1969), house mice, and rats in New Zealand (Marples 1967); it was suggested that the animals were directly or indirectly infected from hedgehogs living in the same habitat.
The activities associated with direct contact between individuals such as fighting and mating probably represent the main source of cross infection between hedgehogs (Morris and English 1973). The hedgehog mites may act as a vector in the transmission due to common coinfection and presence in the nests and soil. Trichophyton erinacei has never been isolated from soil, but it remains viable for up to 1 year in nests. The nests are therefore potential source of infection for other animals and humans (English and Morris 1969).
The presentation in hedgehog ranges from asymptomatic infection to extensive involvement of the body surface. The infection is predominantly located on the head and usually spreads slowly (Morris and English 1973; Takahashi et al. 2002; Schauder et al. 2007). In human, cases of dermatophytosis are localized on contact sites with hedgehog, i.e., extremities (palm, fingers, wrist) are affected in ca 70-80% of reported cases, although tinea corporis, barbae, faciei, capitis, and onychomycosis have been also reported (English et al.
1962; Pierard-Franchimont et al. 2008; Concha et al. 2012).The natural habitats of the main animal hosts are the UK and Northern and Western Europe (Erinaceus europaeus), and the species was introduced into New Zealand with the human immigration. It has been confirmed that Western European hedgehogs became wild in Japan after 1987 or even earlier (Takahashi et al. 2003). The four-toed hedgehog (Atelerix albiventris) is widely encountered in savanna and steppe zones of equatorial Africa from Senegal across to Ethiopia and south to the Zambezi River (sporadic in other regions of Africa). It is smaller than the Western European hedgehog, has a white abdomen, and is characterized by lacking the first toe of the hind leg. Atelerix albiventris has spread all over the world as a pet animal, most of them are domesticated with wild populations reported to be few (Takahashi et al. 2002; Santana et al. 2010).
Since the description of T. erinacei, hundreds of zoonotic infections due to T. erinacei have been reported from hedgehogs and humans across many European countries, Middle East, New Zealand, Australia (humans who handled animals in New Zealand), Africa, Japan, Korea, Taiwan, the USA, and Chile (English et al. 1962; Connole and Johnston 1967; Rosen 2000; Schauder et al. 2007; Pierard-Franchimont et al. 2008; Hsieh et al. 2010; Sun et al. 2010; Concha et al. 2012; Rezaei-Matehkolaei et al. 2013; Sieklucki et al. 2014; Drira et al. 2015; Jang et al. 2016). In an epidemiological survey, T. erinacei was reported in 44.7% of wild hedgehogs in New Zealand (Smith and Marples 1964), 20-25% of wild hedgehogs in Britain (Morris and English 1969) and 29.5% of hedgehogs in France (Le-Barzic et al. 2017). Skin lesions suggestive of dermatophytosis were observed only in ~6% of infected animals (Le-Barzic et al. 2017). The prevalence in household hedgehogs in Japan was 39% (Takahashi et al. 2003) and 50% in Spain (Abarca et al. 2017). The incidence of human dermatophytosis due to contact with hedgehogs is difficult to estimate. When molecular methods are used for species identification, T. erinacei is regularly detected at low frequencies (Sun et al. 2010; Rezaei- Matehkolaei et al. 2013; Hubka et al. 2014b).
Because the hedgehogs are increasingly popular as pets, global prevalence and spread of T. erinacei requires close monitoring. The high infection rate in household hedgehogs predicts that the number of patients will have increasing tendency along with growing popularity of hedgehogs as pets.
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