Differential Diagnosis Between Venomous (Bothrops jararaca, Serpentes, Viperidae) and "Nonvenomous" (Philodryas olfersii, Serpentes, Dipsadidae) Snakebites: Is It Always Possible?

Road Guarder (Conophis lineatus concolor: Dipsadidae): Case documentation of a clinically significant envenoming

Detailed cases of envenoming by a non-front-fanged snake (NFFS) from North, Central, and South America have had limited representation in the toxicology and toxinology literature. The NFFS, Conophis lineatus, has been reported to deliver bites that resulted in moderately severe envenoming. However, most of these reported cases have been via personal communication, or self-reported and lacking in detailed medical evaluations. Reported here is a case of an amateur naturalist who was traveling in Mexico and was envenomed following extensive protracted bites to both hands from a wild Conophis lineatus concolor. There was rapid development of extensive localized edema, intense pain, and ecchymoses. The patient was transported to a hospital and after arrival the administration of antivenom was considered due to the severe appearance of local symptoms. The patient requested the medical team contact a consultant toxinologist who advised against the administration of antivenom because of the absence of any supporting evidence demonstrating therapeutic benefit in treating envenoming by C. l. concolor. Consequently, all treatments were limited to supportive symptomatic care. Despite the development of prominent localized symptoms, all laboratory evaluations, including coagulopathy assessment values, revealed no remarkable abnormal alterations. The patient was discharged after two days and symptoms gradually resolved with two months of supportive care.

An integrative view of the toxic potential of Conophis lineatus (Dipsadidae: Xenodontinae), a medically relevant rear-fanged snake

Most traditional research on snake venoms has focused on front-fanged snake families (Viperidae, Elapidae, and Atractaspididae). However, venom is now generally accepted as being a much more broadly possessed trait within snakes, including species traditionally considered harmless. Unfortunately, due to historical inertia and methodological challenges, the toxin repertoires of non-front-fanged snake families (e.g., Colubridae, Dipsadidae, and Natricidae) have been heavily neglected despite the knowledge of numerous species capable of inflicting medically relevant envenomations. Integrating proteomic data for validation, we perform a de novo assembly and analysis of the Duvernoy's venom gland transcriptome of the Central American Road Guarder (Dipsadidae: Xenodontinae: Conophis lineatus), a species known for its potent bite. We identified 28 putative toxin transcripts from 13 toxin families in the Duvernoy's venom gland transcriptome, comprising 63.7% of total transcriptome expression. In addition to ubiquitous snake toxin families, we proteomically confirmed several atypical venom components. The most highly expressed toxins (55.6% of total toxin expression) were recently described snake venom matrix metalloproteases (svMMPs), with 48.0% of svMMP expression contributable to a novel svMMP isoform. We investigate the evolution of the new svMMP isoform in the context of rear-fanged snakes using phylogenetics. Finally, we examine the morphology of the venom apparatus using μCT and explore how the venom relates to autecology and the highly hemorrhagic effects seen in human envenomations. Importantly, we provide the most complete venom characterization of this medically relevant snake species to date, producing insights into the effects and evolution of its venom, and point to future research directions to better understand the venoms of 'harmless' non-front-fanged snakes.