Bites of the European pigeon tick (Argas reflexus): Risk of IgE-mediated sensitizations and anaphylactic reactions

Background

Local and systemic reactions can occur after bites of Argas reflexus (Argas), a soft tick parasitizing pigeons.

Objective

Risk assessment of IgE-mediated sensitizations and systemic reactions after Argas bites.

Methods

Case histories, skin prick tests (SPTs) with a whole-body extract of Argas containing major allergen Arg r 1, and common inhalants and specific IgE measurements were obtained from 148 subjects who had had Argas bites and 20 volunteers as a control group.

Results

Systemic reactions (urticaria, angioedema, dyspnea, cardiovascular dysregulation, unconsciousness) were reported in 12 of 148 (8%); 146 of 148 (99%) had local reactions. Atopy was found in 37 of 146 (25%) with local reactions and 3 of 12 (25%) with systemic reactions. SPT to Argas was positive in 24 of 148 (16%) with a high proportion of atopics 10 of 24 (42%); specific IgE to Argas was detectable in 12 of 135 (8% of 148) with moderate concordance to systemic reactions. No positive SPT or specific IgE results to Argas were obtained in the control group. Immunoblotting of 23 sera revealed an IgE-binding protein in 19 of 23 sera (82%) at 22 kd, indicating a major allergen of Argas.

Conclusion

Severe anaphylactic reactions were infrequently (approximately 8%) found after bites of the soft tick Argas reflexus. Atopy is a risk factor for skin sensitizations to Argas, but not for systemic reactions after bites by Argas. Using a whole-body extract of Argas, diagnosis through SPT and specific IgE is hampered by false-negative and irrelevant positive results, particularly in atopy.

Key words: Arthropod allergy, pigeon tick, Argas reflexus, tick bite, IgE-mediated reaction, anaphylaxis, whole-body extract, skin prick test, allergen specific IgE

Abbreviations used: LR, Local reaction, NPV, Negative predictive value, PPV, Positive predictive value, r, Recombinant, SPT, Skin prick test, SR, Systemic reaction