From soldiers who had presumably acquired their infections in Pacific war areas, six strains of P. vivax were isolated by transfer of blood to patients who were candidates for malaria therapy. The clinical and parasitological characteristics of the induced infections were not unlike those of infections with McCoy strain of P. vivax, the strain of reference used throughout the study. Some of the patients with known or probable histories of former vivax infections demonstrated considerable immunity to the Pacific strain infections, four patients being refractory.
When gametocytemia of these induced infections seemed to favor mosquito infection, A. quadrimaculatus mosquitoes were fed. Subsequent to a minimum incubation period of 17 days, these mosquitoes were examined for sporozoites. Salivary gland infections were demonstrated in mosquitoes fed on patients with infections with three of the six strains. Sporozoite transmission of these three strains was accomplished. Subsequently the infectiousness to A. quadrimaculatus of patients with two of these strains was studied. It was found that salivary gland infections sometimes developed following the feeding of mosquitoes on patients with submicroscopic gametocytemia.
It is concluded that at least some of the vivax strains from the Pacific war area are capable of being transmitted by A. quadrimaculatus. It is believed that this mosquito is a somewhat less efficient vector for these strains than for McCoy vivax.