A zoonotic ringworm outbreak caused by a dysgonic strain of Microsporum canis from stray cats

Background: Cats are frequent carriers of Microsporum canis and veterinary students are at high risk of exposure and acquisition of the organism a la infeccion. Objectives: An outbreak of zoonotic ringworm carried by a litter of stray cats is described. Four veterinary students, four dogs, and six cats living in five separate locations were affected. All had direct or indirect contact with the infected kitten litter. We tried to identify the causal dermatophyte. Methods: Conventional and mycological culture methods were used. Results: Microscopic features of scrapings and hairs treated with 20% KOH strongly suggested a M. canis etiology, and a diagnosis of ringworm was empirically supported by successful treatment of humans and animals. Nevertheless, cultures failed to show the expected morphology. Conclusions: Culture features of our strain are compared with those described by other authors for dysgonic M. canis strains. Epidemiological features are also discussed.