Hedgehog ringworm.

There is a type of ringworm infection in man that results from contact with infected hedgehogs. Almost half of the hedgehogs in New Zealand carry the fungus that causes it,' 2 named by M. J. Marples and J. M. B. Smith' Trichophyton mentagrophytes var. erinacei. The fungus has also been isolated from hedgehogs in Britain,3 I but reliable figures for its incidence are not yet available. In both countries the discovery of the fungus on hedgehogs was preceded by its isolation from human patients and was the result of a deliberate attempt to trace the source of the human infections. It is perhaps a reflection on British mycology that the disease should have been described first from New Zealand, sincq all New Zealand hedgehogs are direct descendants of British animals introduced into that country about 1885 onwards,5 so that T. mentagrophytes var. erinacei was probably present in Britain at that time. Like other animals introduced into New Zealand the hedgehogs flourished and multiplied, and there is good evidence that the New Zealand population is now very much denser than the British.6 Not surprisingly the incidence of human infections is also much higher there than in Britain. R. A. Quaife7 has recently recorded three patients infected with hedgehog ringworm in Hampshire. He suggests that the incidence of human infection may be increasing, at any rate locally, in Britain; but many more reports of the incidence of the condition will be needed before this can be proved. Possibly the incidence is fluctuating regionally in accordance with changes in the population of hedgehogs. Hedgehog ringworm in man is commoner on exposed sites and often cannot clinically be differentiated from other forms of ringworm. M. P. English and her colleagues2 mention that some cases on the hands were similar to an infected eczematous pompholyx eruption, and one of Quaife's patients is reported as having had blistering and peeling of the skin of the hands. The origin of another uncommon human ringworm, caused by T. persicolor, has recently also been traced8 to a wild mammal-namely, the field vole (Microtus agrestis hirtus). The chance of man coming into direct or indirect contact with voles must be considerably less than with hedgehogs, and this could account for the rarity of the human infection. The fluctuating incidence in man of infection with T. persicolor is probably due to fluctuations in the vole population.