Study on the venom of Bothrops ammodytoides from La Pampa (Argentina) and some toxicological, biochemical and immunological characteristics.

Bothrops (B.) ammodytoides is the southernmost viper species in the world and is endemic to Argentina, where it is distributed from the northwest to southern Patagonia. In La Pampa, northern Patagonia where it inhabits, snakebite incidents are recorded. Its venom has toxic potency comparable to that of other Bothrops species found in Argentina. However, its venom and the effectiveness of available antivenoms have not been studied as extensively as those of other Bothrops species. For this reason, some biochemical, immunological and toxicological characteristics of venoms from snakes of this province were studied. The electrophoretic pattern of the pooled venoms showed the most intensely stained bands in the range of 13-70 kDa. Gel filtration of samples showed 8 peaks in all cases. The toxicity of the venom pool was 51.8 μg, in the range of LD50s known for this venom. Nevertheless, individual samples of venom of specimens from the same locality showed important variability in their lethal potencies. Dermonecrotic and "thrombin-like" activity were not detected, nevertheless hemorrhagic, coagulant, defibrinogenating, phospholipase and proteolytic activities were present. The venoms showed immunochemical reactivity with the antibothropic antivenoms (AV) used in Argentina. The ED50 for neutralization of the pooled venom's lethality was 182 μL (1.42 mg/mL). However, the volume of AV required for neutralizing the same challenge dose varied significantly among individual venom samples. Despite this variability, the AV successfully neutralized the other tested toxic activities. Although the venom samples exhibited low biochemical variation overall, differences in neutralization efficacy suggest some heterogeneity in venom composition or in their components interaction. Nevertheless, the antibothropic AV currently used in Argentina appears effective in neutralizing the toxic activities of B. ammodytoides venom.