Animals as a reservoir of human ringworm in New Zealand.

Abstract

SUMMARY Investigations in New Zealand have shown that animals are an important reservoir of human ringworm. Of 4,328 dermatophytes recovered from human lesions over the six-year period 1963-68, 1,579 (36.5%) were considered to be of animal origin–1,254 (29.0% total) Microsporum canis; 189 (4.4% total) Trichophyton erinacei; 86 (2.0% total) Trichophyton mentagrophytes; 46 (1.1%) Trichophyton verrucosum; 2 Microsporum distortum and 2 Trichophyton equinum var. autotrophicum. Human infection with zoophilic dermatophytes was more pronounced in the younger age groups, showed no marked sex distribution, and usually occurred at only a single exposed site on the body. Apart from the M. canis ringworms which occurred mainly between the months February to August (autumn, winter), no marked seasonal variations were observed. Of the 12 dermatophyte species recovered from 1,290 wild, domestic and laboratory animals examined between 1960-68, only nine were regarded as possessing parasitic properties. These were the zoophilic Microsporum canis, M. distortum, M. nanum, Trichophyton erinacei, T. equinum var. autotrophicum, T. gallinae, T. mentagrophytes, T. verrucosum, and the geophilic M. gypseum. Those regarded as essentially non-pathogenic were the geophilic M. cookei, T. ajelloi and T. terrestre. Apart from T. mentagrophytes which was recovered from a wide variety of animals, the remaining pathogenic dermatophytes displayed marked host specificities. T. mentagrophytes var. quinckeanum was not isolated from any of the human or animal specimens. It is confirmed that, in New Zealand, animals form an important reservoir of human ringworm. Direct contact with small domestic pets rather than larger farm animals is the main source of infection. Of the small wild animals, hedgehogs (Erinaceus europaeus) appear most important.