Venom Variability and Envenoming Severity Outcomes of the Crotalus scutulatus scutulatus (Mojave rattlesnake) from Southern Arizona
(J Proteomics. 2012;75:2576-2587). Massey Dj, Calvete Jj, Sànchez Ee, Et AL
Prepared by Matthew Stewart, MD, University of Utah Emergency Medicine Resident, Salt Lake City, UT, USA
The Mojave rattlesnake is present in the southwestern United States and north central Mexico. Its venom is traditionally composed of 3 phenotypes: the Mojave toxin with neurotoxic effects, snake venom metalloprotease (SVMP) with hemorrhagic effects, and a combination of the two. The goal of this study was to determine the geographical differences of the Mojave snake venom and its correlation to health severity after human envenomation. Using 21 Mojave rattlesnakes, the investigators characterized the venom proteome, geographical distribution, and lethal dose 50 (LD50), and evaluated health severity outcomes in Pima and Cochise Counties of southeastern Arizona. Retrospective chart review from the Arizona Poison and Drug Information Center provided data to assess envenomation severity using the Abbreviated Snakebite Severity Score (ASSS).
Geographically, the Mojave toxin was most common in Cochise County whereas the SVMP phenotype was most common in Pima County. By calculating the LD50, venom potency increased with Mojave toxin and decreased with SVMP. Additionally, the investigators discovered a new toxin phenotype (myotoxin-A) found in the transition zone between the Mojave and SVMP toxins. Neurotoxic effects were higher in Cochise County (9.5%) vs Pima County (1.8%); however, there was no statistical difference in envenomation severity, antivenom administered, days in healthcare facility, or envenomations per 100,000 population. The investigators conclude that although neurotoxic effects correlate with venom phenotypes and geographical distribution, there was no overall significant difference in human envenomation outcome.