A method is described for actively immunizing man against the venom of the tiger snake.
Over a period of 13 months, increasing amounts of venom were injected into a subject who had been repeatedly bitten by venomous snakes, and who was sensitive to horse-serum. The initial dose was 0.002 mg and the final dose 25 mg of venom.
A pre-immunization titer of 0.2 units of antivenene per ml of serum was present. Three months after the commencement of immunization the titer was 1 unit/ml, while at 4 months a titer of 5.1 units/ml was reached. Depending on the interval of time which then elapsed between injections, the antivenene titer fluctuated between 1.5 and 5.2 units/ml. Four months after the final dose a titer of 2 units/ml was still present.
Venom treated with formalin (toxoid) did not exert a detectable antigenic effect.
The health of the patient was not adversely affected throughout the course of immunization, but transitory local reactions frequently followed the injections of either venom or toxoid. On three occasions mild general reactions occurred.
Evidence is supplied which suggests that after active immunization a titer of 1 unit/ml constitutes in an adult a protective level of antivenene against the bite of a tiger snake containing an average amount of venom.
The nature of the local reactions, the protection afforded by active immunization and the indications for active immunization are discussed.
Present address: Prince Henry's Hospital, Melbourne.