Studies of bronchial asthma induced by chironomid midges (Diptera) around a hypereutrophic lake in Japan.

There have been few reports on hypersensitivity to chironomid midges in bronchial asthmatic patients around the area of hypereutrophic natural lakes, which have been notorious as an environmental hazard due to the massive occurrence of adult chironomids during several periods of the year. Our study investigated IgE antibodies to chironomid midges in bronchial asthmatic patients around the Lake Suwa area in comparison with those of the Matsumoto area (control area). A total of 123 adult patients with bronchial asthma were investigated by measurement of IgE antibodies with extracts of three chironomid midges (Chironomus yoshimatsui, C. plumosus, and Tokunagayusurika akamusi), mite, and silkworm. In addition, in the allergy testing, 12 common inhalant antigens were used. Of 123 adult patients with bronchial asthma, 65 (52.8%) produced positive allergy tests. Thirty-three (50.8%) were positive to mite, 28 (43.1%) to silkworm, 11 (16.9%) to C. yoshimatsui, eight (12.3%) to C. plumosus, and three (4.6%) to T. akamusi. We compared our results with the previous reports. The number of positive tests to silkworm in the Lake Suwa area was higher than in other areas. However, C. plumosus and T. akamusi showed a lower number of positive reactions. We considered the lower positive number of C. plumosus and T. akamusi tests in the Lake Suwa area to be related to the advanced age of patients in this area. The chironomids are an important cause of asthma, together with mite and silkworm, in the Lake Suwa area, but affect old asthmatic patients less than asthmatic children.