Plasmodium berghei NK65: studies on the effect of treatment duration and inoculum size on recrudescence.

Recrudescence of Plasmodium berghei NK65 infection was studied to examine factors affecting recrudescence. Treatment with a high dose of chloroquine did not prevent recrudescence, but an extended duration of treatment suppressed the frequency of recrudescence. Infection with a larger number of parasites also resulted in more frequent recrudescences. Recrudescent parasites were as sensitive to chloroquine as those before treatment. Splenectomized mice were administered carbon particles, infected, and treated with chloroquine. Recrudescence was significantly more frequent in these mice than in mice given a sham operation and PBS. The results do not suggest that merozoite stages escape the effect of chloroquine by 'hiding' in phagocytes, but that latent parasites such as dormant ring stages may cause recrudescence.