Toward a more humane intracerebral pathogenicity index that does not compromise virus pathogenicity ratings.

Abstract

Determination of the intracerebral pathogenicity index (ICPI) of a virus requires tracking sick animals until death or until the eighth day of the standard observation period. A more humane procedure would be to painlessly kill sick animals, but such intervention in the standard protocol could compromise the rating of the virus. In this paper, a modified scoring system is proposed, whereby humanely killed animals are given a score that, on average, does not alter the ICPI. The variance of an animal's contribution to the optimum modified ICPI is never greater than the variance of its contribution to the standard ICPI.