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Forensic proof of venomous snakebite is challenging, particularly when the snake species involved is not endemic to the region in which the event occurred. This case report describes postmortem histopathological findings and venom detection following suicide by monocled cobra (Naja kaouthia) envenomation, at a location (Texas, USA) where that animal is not normally encountered. External, internal and histopathological examination was performed according to the standard of the local office of the medical examiner. Tissue homogenate and blood were assayed with a Naja-specific enzyme-linked immunosorbent assay (ELISA), using locally obtained coral snake (Micrurus) venom as negative control. External evidence of puncture marks, edema and erythema were associated with local evidence of microscopic necrosis, acute inflammation, vascular congestion and lymphadenitis. Cobra venom was present in cardiac serum and at higher concentrations in serum, soft tissue and lymph nodes near the puncture sites. In the absence of commercial kits for venom detection, confirmation of snake envenomation postmortem can be achieved by correlation of specific ELISA with local findings. Exclusion of related local snake venom is necessary to confirm the specificity of the assay.

This work evaluated the feasibility of using toxoids obtained by gamma radiation in the production of antivenoms in small and large animals. Mixtures of African snake venoms from viperids or elapids were used. The viperid mixture contained the crude venom of five species of the genera Echis and Bitis, while the elapid mixture contained the crude venom of six species of the genera Naja and Dendroaspis. The viperid mixture had an LD50 of 1.25 mg/kg in mice, and the elapid mixture had an LD50 of 0.46 mg/kg. Both viper and elapid aqueous mixtures were subjected to Cobalt-60 gamma irradiation in three physical states: lyophilized, frozen and liquid. Radiation doses ranged from 0.5 to 100 kGy. The LD50s of the lyophilized and frozen mixtures of both viperid and elapid mixtures remained unaltered with radiation doses as high as 100 kGy; nevertheless, in the liquid state, doses of 3.5 and 5.5 kGy reduced the venom toxicity of both the viperid and elapid mixtures to 7.25 mg/kg and 1.74 mg/kg; less toxic by factors of 5.8 and 3.8, respectively. Groups of four rabbits and three horses were immunized with either irradiated or non-irradiated mixtures. In vitro and in vivo analysis of the rabbit and horse sera revealed that neutralizing antibodies were produced against both irradiated (toxoids) and native venom mixtures. None of the animals used in this study, either immunized with native venom or toxoids, developed severe local effects due to the application of venoms mixtures. Gamma-irradiated detoxified venoms mixtures, under well-controlled and studied conditions, could be a practical alternative for the production of polyvalent equine serum with high neutralization potency against snake venoms.

The most abundant protein families in viper venoms are Snake Venom Metalloproteases (SVMPs), Snake Venom Serine Proteases (SVSPs) and Phospholipases (PLA2s). These are primarily responsible for the pathophysiology caused by the bite of pit-vipers, however, there are few studies that analyze the pharmacokinetics (PK) of whole venom (WV) and its protein families. We studied the pathophysiology, PK profile and differential absorption of representative toxins from venom of Neotropical Rattlesnake (Crotalus simus) in a large animal model (ovine). Toxins studied included crotoxin (the main lethal component), which causes moderate to severe neurotoxicity, SVSPs, which deplete fibrinogen, and SVMPs, which cause local tissue damage and local and systemic hemorrhage. We found that Whole Venom (WV) was highly bioavailable (86%) 60 h following intramuscular (IM) injection, and extrapolation suggests that bioavailability may be as high as 92%. PK profiles of individual toxins were consistent with their physicochemical properties and expected clinical effects. Lymph cannulated animals absorbed 1.9% of WV through lymph during the first 12 h. Crotoxin was minimally detectable in serum after intravenous (IV) injection, however, following IM injection it was detected in lymph but not in blood. This suggests that crotoxin is quickly released from the blood toward its tissue targets.

The venom of the Eastern coral snake Micrurus fulvius can cause respiratory paralysis in the bitten patient, which is attributable to β-neurotoxins (β-NTx). The aim of this work was to study the biodistribution and lymphatic tracking by molecular imaging of the main β-NTx of M. fulvius venom. β-NTx was bioconjugated with the chelator diethylenetriaminepenta-acetic acid (DTPA) and radiolabeled with the radionuclide Gallium-67. Radiolabeling efficiency was 60%-78%; radiochemical purity ≥92%; and stability at 48 h ≥ 85%. The median lethal dose (LD50) and PLA₂ activity of bioconjugated β-NTx decreased 3 and 2.5 times, respectively, in comparison with native β-NTx. The immune recognition by polyclonal antibodies decreased 10 times. Biodistribution of β-NTx-DTPA-(67)Ga in rats showed increased uptake in popliteal, lumbar nodes and kidneys that was not observed with (67)Ga-free. Accumulation in organs at 24 h was less than 1%, except for kidneys, where the average was 3.7%. The inoculation site works as a depot, since 10% of the initial dose of β-NTx-DTPA-(67)Ga remains there for up to 48 h. This work clearly demonstrates the lymphatic system participation in the biodistribution of β-NTx-DTPA-(67)Ga. Our approach could be applied to analyze the role of the lymphatic system in snakebite for a better understanding of envenoming.