In a previous paper (1) it was reported that the simultaneous presence of two strains of Plasmodium vivax apparently delayed the development of an adequate homologous immunity to either strain. The present paper records observations bearing on the ability of anophelines to transmit either or both strains when infected from the patients previously mentioned as concurrently infected with two strains of P. vivax.
In the experiments reported the strains of P. vivax employed are designated as the McCoy and Cuban. Their dissimilarity is indicated not only by the circumstance of their different provenance, but by the results of cross immunity tests as well (2). In this connection it may be recalled that the infectiousness of a patient infected with a single strain of P. vivax very closely coincides with the period of clinical activity (3). We have assumed that both strains of parasites participated in the clinical attack experienced by the patients given the simultaneous double inoculations, and that it is unlikely that the gametogeny of either would be influenced by the presence of the other.