RESISTANCE OF 3 SPECIES OF WARM-BLOODED ANIMALS TO WESTERN DIAMONDBACK RATTLESNAKE (CROTALUS-ATROX) VENOM

The resistance of Sigmodon hispidus (hispid cotton rat), Neotoma micropus (gray woodrat), and Didelphis virginiana (opossum) to C. atrox (Western diamondback rattlesnake) venom was studied by antihemorrhagic assay, hemorrhagic assay, mouse protection test and determination of the LD50. The antihemorrhagic activity of serum and tissue extract was measured in the back of rabbits. In all 3 animals there was very little antihemorrhagic activity associated with tissue extract. There was antihemorrhagic activity associated with the 3 serum samples with the highest being D. virginiana. The hemorrhagic assay in the back of the 3 spp. of animals revealed that D. virginiana and N. micropus would neutralize the hemorrhagic factors in C. atrox venom at about the same rate. S. hispidus neutralized C. atrox venom but to a lesser degree. The LD50 of the venom in S. hispidus was 172 mg/kg body wt, which was 6.5 times less resistant than N. micropus but 21 times more resistant than white laboratory mice. The results clearly show that the 3 animals studied are resistant to rattlesnake venom.