Survival of parasites in mice immunized against Plasmodium berghei

The rodent malaria parasite Plasmodium berghei may survive im immunized Swiss and C3H/StZ mice for a considerable period of time. Despite considerable differences in the observed survival time in animals of a given strain, a general, strain specific pattern is observed. Parasites generally survive longer in Swiss than in C3H/StZ mice. In some of the Swiss mice parasites survived throughout the experimental period, whereas in the others restricted survival was observed, possibly reflecting genetic disparity. Since booster infections did not affect the survival pattern, the effectiveness of elimination is not determined by "antigen" dependent, gradual differences in quality of the hosts' immune response. Repeated biotechnical manipulation of the animals may influence experimental results.