Two hundred and ninety six adult patients consented to these ethically approved studies. In all cases the envenoming snake was identified by a herpetologist or by immuno-assay of the blood.
Serial neurological examinations and jitter estimation by stimulated concentric needle recording from orbicularis oculi were done beginning within 1-7 hours of envenoming and continuing with 67 patients seen at 6 weeks for follow-up.
Krait venom causes paralysis, Russell’s Viper venom has haematological effects and the Hump Nosed Viper bites produce local pain, swelling and necrosis.
Krait and Russell’s Viper envenomed patients showed neurotoxicity as ptosis, blurred vision, ophthalmoplegia, facial bulbar, neck and respiratory and then proximal muscle weakness.
Krait envenomed patients showed paresis on admission with recovery beginning at 30 hours. Russell’s Viper patients showed only ophthalmoplegia with onset by 4 hours and recovery starting after 48 hours. Those bitten by larger Vipers showed more severe toxicity.
Hump Nosed Viper patients showed no neurotoxicity but 3/18 had abnormal jitter values and the group mean jitter values were significantly higher than 29 normal subjects.
Neurotoxicity had resolved by discharge at 5-10 days though jitter was still raised in some. All those seen at 6 weeks had normal jitter values.
The venom of all three snakes produce effects on the neuromuscular junction but it is of no clinical relevance in Hump Nosed Viper; of secondary importance in Russell’s Viper but the paralysis can kill after Krait envenoming.
Krait and Russell Viper envenoming was treated with a multivalent anti-toxin serum. This cleared the circulating toxins from the blood but did not affect the course of the neurotoxicity. There was significant anaphylactic morbidity and mortality due to the antivenom.