Anaphylaxis after Argas reflexus bite

DUE to the growing populations of wild urban pigeons, the natural hosts of parasitic ticks such as Argas re exus (Arg r), there is an increased risk of allergic reactions to tick bites, presumably caused by the proteins secreted by the tick's salivary glands. Allergic reactions with symptoms ranging from local manifestations at the bite site (itching, edema, and erythema) to severe systemic reactions (urticariaangioedema and shock) have been reported in Europe (1±5). Here we report two patients who experienced severe systemic reactions after a bite by Arg r. A 37-year-old man, living in a small town in central Italy near an old building, experienced two severe systemic reactions: the ®rst one with urticaria-angioedema and the second one with cardiovascular failure and loss of consciousness. Both episodes occurred after nocturnal bites by a pigeon tick, identi®ed as Arg r. Clinical history, skin prick test, and speci®c IgE measurements (CAP System, Pharmacia & Upjohn, Sweden) did not indicate any sensitization to common inhalants or food allergens. Total IgE (UniCAP) was 32 kU/l. Interestingly, the patient had experienced local reactions to venom from Apis mellifera (honeybee). Speci®c IgE was detected to A. mellifera (2.34 kU/l, CAP class 2) and to Arg r (5.73 kU/l, CAP class 3). In contrast, no speci®c IgE could be detected to allergens of Dolichovespula maculata, Vespa crabo, Vespula spp., Polistes spp., Solenopsis invicta, Aedes comunis, Chironomus thummi, Tabanus spp., Blatella germanica, and Sitophilus granarius. The second patient was a 26-year-old man, also living in an ancient city of central Italy. He experienced several local reactions to bites of the pigeon tick, subsequently identi®ed as Arg r, before developing two episodes of systemic reactions, with anaphylactic shock, to the tick bite. History, skin prick test, and speci®c IgE to common inhalant and food allergens were negative. Total IgE was 77.1 kU/l; speci®c IgE to Arg r was 1.27 kU/l (CAP class 2). Severe, potentially life-threatening reactions in our patients con®rm former cases of anaphylactic manifestations after Arg r tick bite (2, 3, 5). The patients described were living close to old buildings. Attics or roofs might have served as pigeon breeding sites, and ticks such as Arg r could have migrated to apartments in the neighborhood. Repeated tick bites can induce IgE-mediated sensitization to allergens of the soft tick even in subjects without atopic predisposition. Severe immediate-type systemic reactions, as suggested by the clinical histories, were directly con®rmed by the presence of speci®c IgE to Arg r and indirectly by the absence of speci®c IgE (except for A. mellifera in one case) to other arthropods, including stinging insects, taxonomically different from Arg r. IgE-mediated cross-reactivity between proteins of the tick and other arthropods seems unlikely, in view of the speci®city of the test employed to assess speci®c IgE to Arg r. Future efforts should be made to identify and use recombinant single allergenic proteins of Arg r to demonstrate more accurately an IgE-mediated reaction to pigeon tick bite.