Abstract
Sea snake envenomation is a serious occupational hazard in tropical waters. In Malaysia, the beaked sea snake (Hydrophis schistosus, formerly known as Enhydrina schistosa) and the spine-bellied sea snake (Hydrophis curtus, formerly known as Lapemis curtus or Lapemis hardwickii) are two commonly encountered species. Australian CSL sea snake antivenom is the definitive treatment for sea snake envenomation; it is unfortunately extremely costly locally and is not widely available or adequately stocked in local hospitals. This study investigated the cross-neutralizing potential of three regionally produced anti-cobra antivenoms against the venoms of Malaysian H. schistosus and H. curtus. All three antivenoms conferred paraspecific protection from sea snake venom lethality in mice, with potency increasing in the following order: Taiwan bivalent antivenom < Thai monocled cobra monovalent antivenom < Thai neuro polyvalent antivenom (NPAV). NPAV demonstrated cross-neutralizing potencies of 0.4 mg/vial for H. schistosus venom and 0.8 mg/vial for H. curtus, which translates to a dose of less than 20 vials of NPAV to neutralize an average amount of sea snake venom per bite (inferred from venom milking). The cross-neutralization activity was supported by ELISA cross-reactivity between NPAV and the venoms of H. schistosus (58.4%) and H. curtus (70.4%). These findings revealed the potential of NPAV as a second-line treatment for sea snake envenomation in the region. Further profiling of the cross-neutralization activity should address the antivenomic basis using purified toxin-based assays.
Highlights
Sea snake envenomation affects individuals involved in sea water activities, including swimmers, divers and fishermen
There are more than 10 species of sea snakes in the Malaysian waters, and of these, the beaked sea snake (Hydrophis schistosus, previously known as Enhydrina schistosa) and spine-bellied sea snake (Hydrophis curtus, previously known as Lapemis curtus or Lapemis hardwickii) are the most commonly encountered species, the former because it is often entangled in fishing nets and hauled in with the catch
There are no significant differences (p > 0.05) noted in LD50 values between the three routes for envenoming, indicating that the sea snake venoms share a near-complete systemic absorption from the subcutaneous site of a snake bite. This is likely because the principal lethal toxins of sea snake venoms consist mainly of low molecular mass toxins (α-neurotoxins and phospholipases A2) [17] that are able to cross barrier membranes more effectively like cobra venom toxins [18]
Summary
Sea snake envenomation affects individuals involved in sea water activities, including swimmers, divers and fishermen. Sea snake venoms are highly lethal; the envenomation can result in rapid death through neuromuscular paralysis and/or rhabdomyolysis, which leads to acute kidney injury. The wide distribution of sea snakes in the warm coastal waters makes sea snake envenomation an occupational health hazard for fisheries-related workers. Mishaps happen as the fishermen try to remove them from the nets [4]. These bites, in contrast to cobra and viper bites, are relatively painless and cause no remarkable local inflammation even as the toxins are insidiously absorbed and effectively distributed throughout the systemic circulation, causing rapid death if treatment is not sought in time
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