Comparison of the Protective Effect of a Commercially Available Western Diamondback Rattlesnake Toxo

James McCabe

Beckman Research Institute of City of Hope

Duarte, CA USA

Jim Brockett

ZooToxins LLC

Charles Cates

Cedars-Sinai Medical Center

Los Angeles, CA USA

In 2011, 5,700 incidents of snake envenomation in humans were reported by the American Association of Poison Control Hotlines. The true number of envenomations likely is higher because reporting is not mandatory, many snakebites go unreported, some snakebite victims do not seek treatment, and some treating physicians do not consult with a poison control center. Although the incidence of rattlesnake envenomation in the pet population has not been quantified, it is thought to exceed that for humans (> 150,000 bites/y by 1 estimate) because of a high rate of outdoor exposure and unreported or unnoticed incidents. A conditionally licensed Western Diamondback Rattlesnake (Crotalus atrox) toxoid vaccine is available for administration to dogs and horses at risk for snakebite and is intended to aid in the reduction of morbidity and deaths attributable to rattlesnake envenomation. Manufacturer data and advertisements suggest this CAT vaccine is efficacious against bites from WD rattlesnakes and also provides cross-protection against envenomation from other rattlesnake species. However, analysis of snake venom reveals it to be a complex milieu of peptides and proteins, and venom from related species and subspecies of rattlesnakes can differ markedly in composition. A vaccine that comprises venom from a single species might provide only limited protection against envenomation by other species of rattlesnakes. In California, companion animals are not typically exposed to WD rattlesnakes because these rattlesnakes are found only in sparsely populated areas in the southeast region of the state. Rather, pets are much more likely to encounter Northern Pacific Rattlesnake (Crotalus oreganus oreganus) and Southern Pacific Rattlesnakes (Crotalus oreganus helleri), which inhabit heavily populated and traversed regions of central and coastal California. We will be presenting data that indicates that CAT vaccination offer limited protection against NP rattlesnake venom and NO cross-protection against SP rattlesnake venom.