The diagnosis of envenomation in animals is not difficult if the snake bite has been witnessed, if fang marks have been found or the animal develops multiple signs compatible with snake bite.
Snake envenomation is almost certain if the animal presenting for treatment is developing an illness of sudden onset, shows pupillary dilation, progressively deepening paralysis and has extended blood clotting time.
However, frequently not all these signs are apparent on presentation and signs vary enormously depending on the type of snake, amount of venom injected and time between bite and presentation, thus complicating diagnosis.
The following conditions may be considered as part of the differential diagnosis list:
- The absorption of organo-phosphatic insecticides or poison baits, which can cause the sudden onset of vomiting and salivation
- In small animals, acute prostration from infectious diseases
- Paralysis due to the Australian paralysis tick, Ixodes holocyclus, may superficially resemble snake bite, and in appropriate geographcal areas, ticks should always be looked for on the animal
- Botulism, which also produces a progressive paralysis
- White muscle disease (selenium deficiency) in horses, which can be distinguished from snake bite since, although the foals have trouble standing, they can suck and swallow if held to the mare
Contributed by R. Brooks. Last updated: January 2008
