Microsporum canis A zoophilic dermatophyte, which is a frequent cause of ringworm in humans, especially children. Invades hair, skin and rarely nails. Cats and dogs are the main sources of infection. Invaded hairs show an ectothrix infection and fluoresce a bright greenish-yellow under Wood's ultra-violet light. Distribution: World-wide. Key Features: Distinctive macroconidia and culture characteristics. Abundant growth and sporulation on polished rice grains. Text slide.

163. Young boy showing numerous, circular scaling lesions with distinct erythematous borders following contact with kittens. M. canis was isolated. 163

164. Young girl showing M. canis lesions in chickenpox scars following contact with family cat.

165. A five week old baby showing typical M 165. A five week old baby showing typical M. canis lesions with raised, erythematous advancing borders following contact with several Siamese cats. 165

166. A five week old baby showing typical M 166. A five week old baby showing typical M. canis lesions with raised, erythematous advancing borders following contact with several Siamese cats. 166

167. Typical M. canis scalp lesion showing hair loss and scaling 167. Typical M. canis scalp lesion showing hair loss and scaling. Note small “broken off” infected hairs in the central part of the lesion. 167

168. Large kerion-type lesion consisting of crusts, matted hair, exudate, and scalp debris. M. canis was isolated. (Courtesy Dr D. Hill, Adelaide, S.A.). 168

169. Severe inflammatory kerion lesion and suppurative folliculitis produced by infection with M. canis. (Courtesy Dr T. Turner, Adelaide, S.A.). 169

170. Typical small-spored ectothrix hair invasion produced by M. canis.

171. Culture of M. canis on mycobiotic agar showing a spreading whitish, cottony surface growth with a golden-yellow reverse pigment. Note non-pigmented strains may occur. 171

172. Culture of M. canis on mycobiotic agar showing a spreading whitish, cottony surface growth with a golden-yellow reverse pigment. Note non-pigmented strains may occur. 172

173. Slide culture of M. canis showing typical spindle-shaped, verrucose, thick-walled macroconidia (5-15 cells), often with a terminal knob. A few pyriform to clavate microconidia are also present. 173

174. Dysgonic type of M. canis 174. Dysgonic type of M. canis. Cultures on mycobiotic agar are heaped and folded and yellow-brown in colour. Macroconidia are usually absent in these strains. However, typical colonies and macroconidia of M. canis are usually produced on polished rice grains. Note the dysgonic type colony of M. canis is similar to that of Microsporum ferrugineum. 174

175. M. canis showing good surface growth and sporulation on polished rice grains.