Grain mites: a small epidemie

Pyemotes mites, of which the grain itch mite is the most important for huma n medicine, are ectoparasites of many insect species. Human infestation occ urs only accidentally and temporally. The source materials are most often g rain, straw and plant-based foods. Bites produce an intensely itching urtic arial wheal capped by pin-point vesicles, which often are destroyed by scra tching. Pyemotes dermatitis favours the back,the abdomen and the flexor sid e of the forearms. The mites are barely visible to the naked eye and reside only briefly on hu mans and thus are not found by physicians during clinical examination. When itching starts, the parasites have usually left their hosts. Therefore it is important to investigate the patient's environment and to identify the i nfested materials. We describe an outbreak of Pyemotes dermatitis in at lea st 16 persons, most of them warehouse workers in a hobby mailorder house. I nfested decorative wheat was the source of the problem. Successful eradicat ion was achieved by fumigation of the storage facilities with the insectici de methylbromide. Our cases demonstrate the importance of examination of en vironmental specimens for ectoparasites in cases of unexplained dermatoses. Biological agriculture avoiding insecticides may cause reappearance of thi s almost forgotten skin disease.