Objective: To determine the effect of temperature on lethality of venom from Chironex fleckeri (the potentially fatal box jellyfish).
Design: Venom extracted from nematocysts of mature Chironex fleckeri specimens was exposed to temperatures between 4°C and 58°C for periods of two, five or 20 minutes, and then injected into freshwater crayfish (Cherax quadricarinatus) to assess lethality.
Main outcome measure: Venom lethality, assessed as time to cardiac standstill in crayfish after intramuscular injection.Results: Venom lethality was significantly affected by both temperature (F7,34 = 21915; P < 0.0001) and time of exposure (F2,34 = 9907; P < 0.0001). No significant loss of lethality was seen after exposure to temperatures ≤ 39°C, even after 20 minutes' exposure. At temperatures ≥ 43°C, venom lost its lethality more rapidly the longer the exposure time. Venom was non-lethal after exposure to 48°C for 20 minutes, 53°C for five minutes, and 58°C for two minutes.
Conclusion: Exposure to heat dramatically reduces the lethality of extracted C. fleckeri venom. Although heat application may be of limited use in treating C. fleckeri envenoming because of the speed of symptom onset, its use in other box-jellyfish envenomings, such as Irukandji syndrome, requires investigation.
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