Preventing Anaphylaxis to Venom of the Jack Jumper Ant

Myrmecia pilosula (the jack jumper ant, JJA) is the principal cause of ant venom anaphylaxis in Australia. Our main objectives were to establish the epidemiology and natural history of JJA allergy, and to determine the efficacy of JJA venom immunotherapy (VIT). We found the prevalence of JJA sting allergy to be 2.7% in the Tasmanian population. People aged >35 had a greater risk of both sting allergy and hypotensive reactions. During follow-up, 79 (70%) of 113 accidental jack jumper stings caused systemic reactions. Prior worst reaction severity predicted the severity of follow-up reactions. Sixty-eight otherwise healthy JJA allergic adult volunteers were then enrolled in a randomised placebo controlled clinical trial of VIT. This was found to be highly effective in prevention of JJA sting anaphylaxis. A number of clinical observations were made during anaphylactic reactions in the placebo group that suggested neurocardiogenic mechanisms &/or direct cardiac effects could be important factors in some anaphylaxis deaths. We also assessed a number of in vitro assays, none of which were found to correlate well with the clinical effect of VIT.