Allergic reactions to Triatoma bites.

Background: Triatoma bugs are best known in the medical community as vectors of trypanosomiasis (Chagas disease). However, bites of Triatoma bugs are a cause of local cutaneous reactions and anaphylaxis, mainly in the western and southwestern United States. The reactions typically occur at night during sleep, and the bite may not be recognized. There is continuing public interest in medical complications of bites of these bugs, although the scope of the problem remains undefined.

Objective: To review the relevant medical literature, identify present knowledge, and determine future research goals for allergy to Triatoma.

Data Sources: Computerized databases were used to search the medical literature for articles in the English language on Triatoma bites, allergy and entomology, and Chagas disease.

Study Selection: Almost all identified articles on Triatoma allergy were used. Only selected articles on Triatoma bites and entomology were pertinent to the objectives. Articles on Chagas disease were limited to cases in the United States.

Results: Bites of Triatoma bugs have been known to cause anaphylaxis for more than a century. These insects inhabit a large area of the United States, but to date most reports of allergic reactions to their bites have originated in the West and Southwest. The reactions typically occur at night during sleep following a bite on uncovered skin and may be unrecognized. Procalin has been identified as the major salivary allergen of Triatoma protracta and was recently cloned and expressed through recombinant technique. Allergenic reactivity has been demonstrated to salivary gland extracts of 2 species. The extracts of these 2 species have not shown immunologic cross-reactivity. Immunotherapy using a salivary gland extract appeared to be beneficial in a small number of patients; however, no commercial testing or treatment allergen is available.

Conclusions: Triatoma bites appear to be an important cause of anaphylaxis, especially in the western and southwestern United States. Because exposure to these insects often occurs during sleep, the incidence of allergic reactions to them is unclear. An epidemiologic study should be performed to determine the incidence, prevalence, and range of allergic responses to the bites of these insects. The lack of commercial antigen limits diagnostic and treatment capabilities. The development of an allergen under the Orphan Drug Act should be encouraged.