Case reports of envenomation and venom composition differences between two Arizona populations of the Southwestern Speckled Rattlesnake, Crotalus pyrrhus (Cope, 1867)

Envenomations by the Southwestern Speckled Rattlesnake (Crotalus pyrrhus) are fairly rare. Previous descriptions in the literature do not include locality, an important factor in the clinical symptoms or syndromes of snakebites resulting from geographic variation in venom composition. Here, we describe two cases of envenoming by C. pyrrhus from two Arizona localities (Tinajas Altas Mountains, Yuma County, and Phoenix Mountains, Maricopa County). Both patients experienced swelling, but neither demonstrated coagulopathy, thrombocytopenia, or hypofibrinogenemia. The Phoenix Mountains patient developed hemorrhagic bullae and tissue damage in his bitten extremity, necessitating the amputation of the distal portion of his middle finger. Treatment for both consisted of medication for pain, isotonic crystalloid, and antivenom therapy with recovery in each case. Based on visual inspection of 1D-gels and RP-HPLC chromatograms, venom samples were largely similar but appeared to differ quantitatively for several toxin families between and within populations. •We describe two cases of human envenomation, from two localities, by the Southwestern Speckled Rattlesnake.•Swelling was present in both cases; neither patient demonstrated coagulopathy, thrombocytopenia, or hypofibrinogenemia.•Amount of necrosis differed between the two bites, necessitating amputation of the distal portion of middle finger for one patient.•1-D gels and RP-HPLC chromatograms appeared to show quantitative but not qualitative venom differences between localities.