Effect of some variables on the in vivo determination of scorpion and viper venom toxicities.

An adequate assessment of scorpion and snake venom LD50 is an important step for accurate evaluation of antivenom sera potencies and the optimization of serotherapy. The LD50 variation of Tunisian scorpion (Androctonus australis garzonii: Aag and Buthus occitanus tunetanus: Bot) venoms with body weight, sex and strain (Swiss or C57BI/6) of mice used, the route of venom injection, the venom-milking procedures (manually or electrically) and the venom batches have been studied over a 7-year period (1990-1996). Aag venom is 3-4 times more toxic than Bot venom. However for both venoms, the LD50 determined in C57BI/6 mice, in small body weight animal or by intraperitoneal route were respectively significantly lower than those determined in Swiss mice, in high body weight or by subcutaneous route. Significant LD50 variations (25-50%) were also seen from one electrically prepared batch to another. A good correlation (r = 0.982) was observed between the concentrations of the crude venom toxic fraction determined by ELISA and LD50 values when assessed in vivo. The LD50 variation of Tunisian viper (Cerastes cerastes: Cc and Vipera lebetina: VI) venoms with the strain (Swiss or BALB/c), sex and body weight of mice used, the season and the year of venom milking were also investigated over a 3-year period (1990-1992). No significant LD50 variations were observed with the mouse strain, the sex or the season of venom milking. However, LD50 varies significantly with the year of the venom collection and the body weight of mice used. Furthermore, SDS-PAGE analysis shows annual variation for VI venom composition where no such variations were observed for Cc venom. These results stress the need either for the standardization of the venom LD50 evaluation or of the venom quality used for the development of an efficient antivenom.