Effect of stress conditions on the course of trophozoite-induced Plasmodium yoelii nigeriensis in mice recently cured of a previous infection.

The effect of stress conditions on the course of trophozoite-induced Plasmodium yoelii nigeriensis in mice recently treated for a previous infection was studied. It was found that when the mice were infected with up to 5943 parasites within 6 days of treating a previous infection, no patent infection was recorded. However, an inoculum of 7924 parasites induced parasitaemia, with a long period of prepatency and a short course of infection before the parasites died out.

Laboratory transmission of Schistosoma mansoni in brackish waters; survival and infectivity of cercariae.

Schistosoma mansoni cercariae were exposed to various dilutions of sea water, both in the absence and in the presence of mice. It was found that whereas 100% and 75% sea water were lethal to the parasites, the parasites survived in lower concentrations of sea water. The lower the concentration the longer was the survival time.