ANALYSIS OF THE SINGLE DILUTION METHOD OF TITRATION OF PSITTACOSIS VIRUS

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Abstract
Investigation of the results of titrations of a single frozen lot of psittacosis virus in eggs obtained from different flocks, and from the same flock at different times revealed significant differences in susceptibility, both from flock to flock and from time to time. Measurement of the survival time after injection of virus into different groups of eggs revealed that the eggs may vary significantly both in uniformity of response and in mean survival time after injection of given dose of virus. The latter fact makes it impossible to compare psittacosis virus titrations based on survival time alone when the titrations are done at different periods. A method of titration is described which allows estimates of potency based on survival time of eggs following injection of a single dose of virus, combined with a standard LD50 titration.