Tick killing in situ before removal to prevent allergic and anaphylactic reactions in humans: a cross-sectional study

Abstract

Background: Tick anaphylaxis is a potentially fatal out- come of improper tick removal and management.1,2 Objectives: To investigate whether killing ticks in-situ with ether-containing sprays or permethrin cream, before careful removal by the mouthparts could reduce this risk. Method: This was a prospective study at Mona Vale Hospital Emergency Department (ED) in Sydney, New South Wales (NSW), over a six-month period during the peak tick season of 2016. Tick removal methods, aller- gic/anaphylactic reactions were recorded for patients pre- senting with ticks in-situ or having already removed the ticks themselves. Primary endpoint was allergic/anaphy- lactic reaction after tick killing/removal. Results: One hundred and twenty-one patients met study inclusion criteria. Sixty-one patients (28 known tick- hypersensitive) had ticks killed with Wart-Off Freeze® (dimethylether, Pharmacare Laboratories Pty Ltd.) or Lyclear Scabies Cream® (5% w/w permethrin, Johnson & Johnson Pacific Pty Ltd.) before removal with fine-tipped forceps or Tick Twister® (O’Tom, France). Three patients (2 known tick-hypersensitive) had allergic reac- tions (5%), none anaphylactic. The 2 known hypersensi- tive patients suffered reactions during the killing process and the third patient had a particularly embedded tick meaning it could not be removed solely by mouthparts. Fifty patients presented to the ED post-tick removal by various methods, none using either fine-tipped forceps or Tick Twister®, of which 43 (86%) experienced allergic reactions – two anaphylactic. Five patients suffered aller- gic reactions before presentation despite no attempt at kill or removal, but ticks had likely been disturbed by some other method. Five patients had live ticks removed in ED – 3 refused killing and had no reaction despite 1 having known hypersensitivity; 2 had ticks on eyelids contraindicating killing, 1 with known hypersensitivity but both had allergic reactions post-removal. Conclusion: Results support killing ticks in-situ before careful removal by mouthparts to reduce allergic/anaphy- lactic reactions although further research is still required.