IMMUNITY IN MALARIA

Abstract

In naturally acquired human malaria there are several reasons why it is almost impossible to know the status or duration of immunity. Since neither quinine nor atebrin eradicates the parasites but merely converts an active infection into a latent one, there is no means of determining precisely when a complete cure takes place. Considerable aid was given to the study of this problem when it was found possible completely to eradicate an acute or chronic Plasmodium knowlesi infection in the rhesus monkey by giving a single dose of sulfanilamide by mouth. Proof that this procedure would sterilize the infection promptly was the inability to produce an infection by subinoculation with massive amts. of the treated animal''s blood although, as previously stated, < 10 parasites con stitute a minimal infective dose; the failure to evoke a relapse by splenectomy; the non-infectiousness of the emulsified spleen; and finally susceptibility to reinfection with the same organism. Quinine or atebrin is unable to accomplish this effect even when given up to their toxic limits over long periods. The ability of sulfonamide drugs now in current use to eradicate P. knowlesi infections has an implication in the problem of human malaria. Although thus far none has been discovered to be as efficient against the human infections, the possibility of such a discovery is not remote. If one should be found it will probably also serve as a true causal prophylactic, something entirely lacking at present.