Code of Federal Regulations Title 9. Animals and Animal Products § 9.113.101 Leptospira Pomona Bacterin

(1) Vaccinates. Inject each of at least 10 but not more than 12 young adult hamsters, each weighing 50 to 90 grams, with 0.25 ml of the diluted bacterin either subcutaneously or intramuscularly, in accordance with the label recommendations for use.

(2) Controls. Retain at least 10 but not more than 12 additional hamsters from the same group as unvaccinated controls.

(3) Challenge. From 14 to 18 days postvaccination, challenge each of 10 vaccinates and each of 10 controls intraperitoneally with a suspension of virulent Leptospira pomona organisms, using a dose of 10–10,000 hamster LD₅₀ as determined by titration.

(4) Post-challenge period. Observe the vaccinates and controls for 14 days post-challenge and record all deaths. If eight or more controls die of leptospirosis, the test is valid and the results shall be evaluated according to the following table:

(5) If three or four vaccinates die in the first stage, the second stage shall be conducted in a manner identical to the first stage.

(6) If the second stage is used, each serial shall be evaluated according to the second part of the table. On the basis of cumulative results, each serial shall either pass or fail.