The toxicity of Physalia physalis: systematic review and experimental study

Jellyfish poisonings are frequent in coastal areas of temperate latitudes. In Spain, the most frequent and dangerous jellyfish is the Portuguese man-of-war or Physalia physalis. Although the clinical manifestations of P. physalis envenomation are known, the acute management and complications are controversial, with varying criteria about proper treatment.

This paper presents a systematic review of those studies that have collected clinical aspects of the sting of P. physalis, as well as an experimental study that evaluates the discharge capacity of nematocysts under different conditions (heated seawater at 50°C, 4°C seawater, distilled water, 25% commercial vinegar, distilled water, 25% commercial vinegar in seawater) as a proxy for envenomation potential including in sea lice. Also, discharged and undischarged nematocyst count was performed in air-dried tentacles at different times after specimen collection.

Acetic acid does not produce nematocyst discharge when diluted in seawater and warm seawater is an optimal rinsing agent that dissolves the jellyfish mesoglea. Furthermore, the nematocysts detached from the jellyfish body maintain toxic capacity for at least 120 days after the stranding of the organism.

Most controversy regarding the treatment of P. physalis envenomation is related to the lack of proper species stratification or identification. In our sample, acetic acid does not elicit nematocyst discharge by itself, but depending on the solvent. Both vinegar and hot seawater rinses are the best first-aid treatments. A first aid protocol is proposed based on data from the review and the experimental study.