Suspected anaphylaxis and lack of clinical protection associated with envenomation in two dogs previously vaccinated with Crotalus atrox toxoid.

Objective: to describe the clinical presentation of two canines present in anaphylactic shock secondary to rattlesnake envenomation. In both cases, there was no previous documented previous envenomation event and the initial sensitization required for anaphylactic response is believed to be secondary to Crotalus atrox toxoid vaccine.

Case Description: In the first case, a 12-year-old golden retriever present for collapse, severe hematochezia, and vomiting after first time envenomation from a suspected western diamondback rattlesnake. The patient presented in severe hypovolemic shock and required aggressive fluid therapy, antivenom, anti-emetics, and pain management. The patient made a full recovery within 24 hours. In the second case, an 8-year old English setter presented for acute collapse, vomiting, and facial swelling after suspected first time envenomation from a suspected Prairie rattlesnake. The patient presented in severe hypovolemic shock with cardiac arrhythmias and required aggressive fluid therapy, antivenom, pain control, anti-emetics, and antibiotics. The patient made a full recovery after three days of hospitalization. Both patients had been previously vaccinated with the C. atrox vaccine.

Conclusion: This case report documents suspected anaphylaxis in two canine patients after first time envenomation by a rattlesnake. Both patients were previously vaccinated by the Crotalus atrox toxoid, which is hypothesized to be the initial inciting trigger.