More on venom activity from Vilas Hiremath at United Labs:
Dear George, I have spiked afibrinogenemia plasma with Russell viper (RV) and saw-scaled viper (Echis, SSV) crude venom. Prothrombin time (PT) and partial thromboplastin time (PTT) both failed to correct with RVV. The PT, but not the PTT, corrected to within the normal range with SSV. This appears to mean that SSV does not need fibrinogen to clot but RVV does need fibrinogen to clot. Your comments please.
Hello again, Vilas, and thank you for another challenging venom question. I suspect your SVV preparation is contaminated with fibrinogen. SVV activates coagulation at the level of prothrombin, but requires fibrinogen to form a clot. You may wish to analyze both venoms for contamination in order to accurately assess their activity. I will again ask Dr. Mary Ann McLane, venom expert, for a further discussion.