Viruses, Serums, Toxins, and Analogous Products; Revision of Standard Requirements for Clostridium Perfringens Types C and D Toxoids and Bacterin-Toxoids

We are amending the regulations pertaining to the Standard Requirements for Clostridium Perfringens Type C and Clostridium Perfringens Type D toxoids and bacterin-toxoids. The amendments will reduce the minimum number of rabbits required in order to pool their serum for testing. This amendment will also clarify the method of determining the test vaccine dose in rabbits based on the recommended vaccine dosage in cattle and other host animal species. These amended regulations will not change the accuracy of the assays and, under certain circumstances, will reduce the number of required tests as well as the number of mice needed for testing. The amendment is necessary to make the potency assays conform more closely to the revised standard requirements for Clostridium Novyi and Clostridium Sordellii Bacterin-Toxoids and more economical to run when combination products containing these fractions are tested.