INHALANT ALLERGY TO THE SCREWWORM FLY. PRELIMINARY REPORT

Specific sensitization to the common housefly (Musca domestica) not related to insect panallergy

BACKGROUND

Allergy to houseflies is rare. We report a case of respiratory allergy from occupational exposure to houseflies in a farmer.

CASE REPORT

A 30 year-old female farmer with a long-standing history of grass pollen allergy observed for 2 years rhino-conjunctivitis and mild asthma when entering livestock stables and barns. Allergy retesting revealed sensitization to various pollens but not to animal danders. Houseflies (Musca domestica) occurring on the farm in great quantity were suspected by the farmer herself as the causative agent.

RESULTS

Skin prick testing with housefly was positive in the patient and negative in four controls. Experimental radioallergosorbant test was class 3 positive. Sensitization to house dust mite, storage mites and cockroach was not detectable. Western blots with housefly extracts revealed immunoglobulin E (IgE)-binding to bands of 70, 50, and approximately 16 kDa. Tropomyosin in the housefly extract (35 kDa) was recognized by a tropomyosin reference serum but not by the patient. In enzyme-linked immunosorbent assay (ELISA) inhibition assays using housefly as the solid phase, IgE-binding of the patient was inhibited by 75% by M. domestica and by 44% by the closely related lesser housefly (Fannia canicularis), but not by extracts from blowfly (Lucilia spp.), fruit fly (Drosophila spp.), horsefly (Haematopota pluvialis) and mosquito (Culex pipiens). The IgE-binding of the tropomyosin control serum was inhibited by 60-80% by all species.

CONCLUSIONS

In accordance with previous reports, this case demonstrates that respiratory sensitization to insects may be highly specific. According to ELISA inhibition, cross-sensitization in the present case was restricted to species of the family of true flies (Muscidae).

Inhalant allergy to arthropods. Insects, arachnids, and crustaceans

Inhalant allergy to arthropods is of major social, economic, and medical importance. As seen in this review, immunologic techniques for evaluating the multitude of clinical problems that are known to exist are beginning to enable the clinical allergist to deal with these problems in more effective ways. Successful application of newer biotechnology methods in areas of protein isolation, characterization, and sequencing together with gene cloning technology should result in significant advances in our understanding and management of inhalant arthropod allergy.

Occupational allergy in an entomological research centre. II. Identification of IgE-binding proteins from developmental stages of the blowfly Lucilia cuprina and other species of adult flies

Sera from 30 workers in an entomological research institute and from five Sydney asthmatics, all with serum IgE antibodies to sheep blowfly (Lucilia cuprina) antigens, were studied with the aim of identifying individual IgE-binding proteins in extracts of L. cuprina adult flies, larvae and eggs, and in extracts of related species of flies from the order Diptera. Using protein blotting, 21, 18 and nine different IgE-binding components were identified in extracts of L. cuprina adult flies, larvae and eggs, respectively. A component(s) of MW 67 kD found in all three developmental stages, showed the highest frequency of IgE-binding; reacting, for example, with 70% of the sera tested with the adult fly extract. Some components were detected in only one of the three developmental stages. Investigations of possible allergenic cross-reactivity between L. cuprina and extracts from six other related species of flies revealed IgE-binding bands in each of the extracts as well as in an extract of Agrotis infusa, a cutworm not belonging to the order Diptera. One strongly reacting component of MW 20 kD was detected in extracts of five different fly species as well as in the A. infusa extract. The results suggested that allergenic cross-reactivity between some fly species exists, and may extend to taxonomically unrelated insect species.

Inhalant allergy following occupational exposure to blowflies

An allergic reaction, provoked by exposure to the blowfly Lucilia cuprina and shown to be IgE-mediated, occurred in a subject employed in an entomological research laboratory. The subject's serum, and sera from three other asthmatic patients with IgE antibodies to blowfly extracts, also reacted with extracts from the screw-worm fly (Chrysomya bezziana). Results suggested that antigens from the two species share immunological cross-reactivity. Cross-reactions also exist between the different developmental stages of both species. Allergic reactions to inhaled insect allergens may not be uncommon in the Australian community.