[Standardization of the control technics of Clostridium perfringens vaccine. Use of a reference vaccine]

Control of Cl perfringens toxins. It is possible to employ a standardized technique for the control of the toxins of Cl. perfringens. Titres of LD50 per ml for the mouse and L+/50 per ml may be expressed with a confidence limit of 1.5. The assay of toxins by L+/50 (relating to their antigenic value) permits the establishment of standards by which it is possible to obtain a satisfactory vaccine with a high degree of certainty. 10 L+/50 per dose for Cl. perfringens A 20 L+/50 per dose for Cl. perfringens B 180 L+/50 per dose for Cl. perfringens C 50 L+/50 per dose for Cl. perfringens D Control of vaccine values. Technique adopted : Determination of antibodies in the rabbit following vaccination. The confidence limit of the antitoxin titre is similarly equal to 1.5 when P = 0.05. It would not appear to be necessary to establish minimum levels of antibodies to confer protection; it seems nevertheless that the results are influenced by considerable variations attributable to the animals used for the most part and that a reference vaccine is required. Freeze-dried vaccine. There is a natural antigenic activity in the rabbit which retains a considerable part of its antigenic properties after maintenance for one week at +37 degrees C. In our view this would be suitable for a reference vaccine.