Venomous animals: clinical toxinology.

Venomous animals occur in numerous phyla and present a great diversity of taxa, toxins, targets, clinical effects and outcomes. Venomous snakes are the most medically significant group globally and may injure >1.25 million humans annually, with up to 100 000 deaths and many more cases with long-term disability. Scorpion sting is the next most important cause of envenoming, but significant morbidity and even deaths occur following envenoming with a wide range of other venomous animals, including spiders, ticks, jellyfish, marine snails, octopuses and fish. Clinical effects vary with species and venom type, including local effects (pain, swelling, sweating, blistering, bleeding, necrosis), general effects (headache, vomiting, abdominal pain, hypertension, hypotension, cardiac arrhythmias and arrest, convulsions, collapse, shock) and specific systemic effects (paralytic neurotoxicity, neuroexcitatory neurotoxicity, myotoxicity, interference with coagulation, haemorrhagic activity, renal toxicity, cardiac toxicity). First aid varies with organism and envenoming type, but few effective first aid methods are recommended, while many inappropriate or frankly dangerous methods are in widespread use. For snakebite, immobilisation of the bitten limb, then the whole patient is the universal method, although pressure immobilisation bandaging is recommended for bites by non-necrotic or haemorrhagic species. Hot water immersion is the most universal method for painful marine stings. Medical treatment includes both general and specific measures, with antivenom being the principal tool in the latter category. However, antivenom is available only for a limited range of species, not for all dangerous species, is in short supply in some areas of highest need, and in many cases, is supported by historical precedent rather than modern controlled trials.