DIETARY FISH OILS AND LONG-TERM MALARIA PROTECTION IN MICE

Previous studies indicate a suppressive influence of fish oils on rode nt malaria. The present work was carried out to study (i) the dose-eff ect relation between dietary fish oils and lethality of primary malari a infection in mice; (ii) the modifying influence of vitamin E; and (i ii) the effect of previous fish oil feeding on parasitemia and lethali ty of a rechallenge infection. For two or four weeks, groups of weanli ng male mice were fed a standard laboratory diet or one of eight purif ied diets containing various amounts of fish oil (providing 6-21% of e nergy). The diets were prepared with and without vitamin E. After the two-or four-week feeding period, the mice were injected intraperitonea lly with Plasmodium yoelii yoelii-infected erythrocytes. Six months af ter the primary infection (four months after discontinuing fish oil fe eding), the surviving mice were again injected intraperitoneally with parasitized red blood cells (or even better-erythrocytes, erythrocytes are used elsewhere). Primary malaria infection was lethal in mice fed standard diet alone or with fish oil and vitamin E added. In contrast , feeding a fish oil-based diet without vitamin E improved survival to at least 70% if the mice had been fed these diets for four weeks. Pro tection against malaria did not seem to be related to the fish oil dos e used. Regardless of the previous fish oil dose, all the mice survivi ng the primary infection survived the rechallenge infection with low p arasitaemias. The results suggest that the prooxidant nature of highly unsaturated fatty acids in fish oils may beneficially influence malar ia infection, and may also increase the resistance against reinfection for some time after discontinuing fish oil intake.