Serum sickness in a dog associated with antivenin therapy for snake bite caused by Crotalus adamanteus

Objective: This case report describes antivenin‐associated acute and delayed hypersensitivity reactions in a dog envenomated by an Eastern diamondback rattlesnake (Crotalus adamanteus), specifically reviewing the syndrome of antivenin‐associated serum sickness. Clinician awareness of this syndrome is important in order to allow for its recognition and appropriate treatment. Case summary: A Boxer dog was envenomated by an Eastern diamondback rattlesnake. Shock, echinocytosis, and coagulopathy were manifested, and the dog was given antivenin crotalidae polyvalent therapy and supportive care. The early onset of an anaphylactoid reaction was attributed to antivenin therapy and was managed with diphenhydramine and subcutaneous epinephrine therapy. Fever, chemosis, and limb edema occurred during the 3rd through 6th hospital days following antivenin therapy and were consistent with serum sickness syndrome as described in humans. Further immunoassay support reflecting complement activation and response to treatment were characteristic. New information provided: To our knowledge, this describes the first reported case of antivenin‐associated serum sickness in a dog.