Epidemiological survey of Microsporum canis infection diagnosed at Nagasaki University Hospital for 20 years (1996-2015)

Motoi Takenaka 
(Nagasaki Univesity Hospital, Department of dermatoallergology),
 Katsutaro Nishimoto  (Japan seafarers relief association Nagasaki hospital)

 In Japan, the Microsporum (M.) canis infection had been reported since 1990’s as a causative fungus species of an increasing tinea corporis and tinea capitis patients. ON the other hand, since 2001 in Japan, Trichophyton (T.) tonsurans infections (tinea capitis and tinea corporis) were become reported increasing especially among the high school students related to contact sports combined with the remarkable decrease M.canis infection. We examined the trend of the M.canis infectious disease.
  The clinical samples that gathered from tinea patients had been send mainly by dermatologists of Nagasaki　area. Identification of dermatophytes was made by macro- and micro- morphology of primary isolates and for the difficult strains, the molecular biological examination.
  We report the transition of the increase of M.canis infection examined at Nagasaki University Hospital comparing the data obtained as a groups of 1996-2000, 2001-2005, 2006-2010 and 2011-2015. The number of all dermatophyte strains isolated were 10177 (1996-2000), 10347 (2001-2005), 7573 (2006-2010) and 3244 (2011-2015). M.canis was identified 196 cases (1.2%), 123 cases (1.2%), 145 cases (1.9%), 170 cases (5.2%), respectively, showing the isolation rate of M.canis tend to increase. 
 Intra animal transmission was examined and 157 cases in 634 (24.8%) were confirmed to relate with pet animals, especially cats. With the cases of familial occurrence, the rate increased up to 60.4%. Concerning age distribution, with female patients (total of 387 cases), under 19 years (0-9 years old: 83 cases, 10-19 years old: 74 cases) and over 60 years (75cases) accounted for the most. With male patients (total of 156 cases), under 9 years old (86 cases) were affected most. Recently the increase of female cases of 60 years old was conspicuous.
 The results concerning M.canis were compared with those of T. rubrum and T. tonsurans, two representative dermatophyte species isolated during the same period not only in Nagasaki prefecture but also in Japan.  T. rubrum was isolated most as a causative species of tinea corporis (70.6% among 4110 cases examined) of all age groups, followed by T.tonsurans (9.4%). T.tonsurans was isolated, especially since 2006, mainly from the young patients engaging contact sports. 
 In conclusion, M.canis is proved still an important dermatophyte species in Nagasaki prefecture among children and aged female suggesting their frequent contact with pet animals. 