Numerous terrestrial and marine animals may envenomate humans, with children overrepresented among the victims*. Treatment, in some cases, may include mechanical ventilation and intensive cardiovascular support, as well as the application of specific therapies and, in some cases, the administration of antivenom. This chapter describes some of the more common animals, their toxins, and the injuries that they cause, and outlines treatment appropriate for each. Snakebites and scorpion stings cause most deaths and morbidity. Envenomation is, for most clinicians, rarely encountered, but if missed, may have catastrophic effects on the victims. It is therefore important to have a high index of suspicion for envenomation, when circumstances and clinical presentation would suggest that this is a possibility, and also to seek advice early from experts in the field when treating these patients.
Snakebite is most common among highly populated rural communities in tropical developing countries. The annual incidence of snakebites, according to the World Health Organization, is 5 million bites leading to 2.5 million envenomations and 100,000 to 200,000 deaths, of which about 50,000 occur in India. Many more survivors have significant handicaps. A worldwide lack of antivenoms contributes to this neglected public health problem.
Medically significant venomous snakes are from 2 major families: the Elapidae and Viperidae. Elapids are front-fanged terrestrial snakes, including dangerous Australian snakes (taipan, brown, death adder, tiger, and black snakes); the cobras, mambas, and kraits of Asia and Africa; and the coral snakes of the Americas. Elapid venoms are highly neurotoxic with an additional cytotoxicity in some species, such as spitting cobras. Vipers, including the rattlesnakes of the Americas and vipers, have large front-folding fangs and venom that is, generally, less systemically toxic than that of the elapids, but is notable for inducing bite-site swelling and local tissue destruction.
Snake venoms are complex mixtures of toxic and nontoxic substances, mostly proteins, that have neurotoxic, myotoxic, procoagulant, anticoagulant, cytotoxic, and hemolytic properties. Many are metalloproteinases and phospholipases.
The diagnosis may be unclear in young children or others unable to give a clear history (eg, those found unconscious) or bitten at night or in dense scrub where snakes may not be seen. The differential diagnoses of venomous snakebite include nonvenomous snakebite or a bite or sting by another venomous creature, stroke or head injury, neuropathy (eg, Guillain-Barré syndrome), metabolic disturbance, allergic reaction, toxin ingestion, or sepsis.
DIAGNOSIS OF ENVENOMATION
There should be a high index of suspicion for a diagnosis of envenomation when children become suddenly unwell in areas where snakes exist, alongside a constellation ...