An evaluation of the mouse bioassay applied to extracts of 'diarrhoetic' shellfish toxins

The standard mouse bioassay, used to assess 'diarrhoetic shellfish poison' (DSP), is based on intraperitoneal administration of toxic mussel extracts, and monitoring of survival time within a 24-hr period. Toxic effects on mice were examined for extracts of mussel samples from two different regions of south Norway known to possess toxins of specific properties. Both samples revealed an exponential pattern in the dose-response relationship. Whereas the time lag from injection to death was linearly dependent on mouse weight, the effect of weight also increased with decreased sample toxicity. When tested with doses adjusted for weight, a marked individual variation was found within all size groups of mice. The results imply that, regarding prohibition limits for distribution and sale of mussels, a certain degree of variation with regard to time should be accepted in the testing of parallel samples. On the basis of the results, a revised method for the determination of toxicity by mouse bioassay is proposed for DSP testing. The method is based on administration to two mice of size-adjusted doses of extracts, followed by a 4-hr surveillance period and a 1-hr upper limit of acceptable time variation between parallel samples. The method shows advantages regarding savings of time and money, in precision in determination of toxicity level, as well as curtailed exposure to toxin and reduced suffering of laboratory animals.