On the Varying Infectiousness of Different Patients Infected with Vivax Malaria

Mark F. BoydStation for Malaria Research, Tallahassee, Florida

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Patients infected with Plasmodium vivax exhibit a wide difference in their infectiousness for Anopheles quadrimaculatus.

Based on the infection resulting in anophelines, patients have been distinguished as “good” and “poor” infectors. These have not in general differed markedly in gametocyte densities, except that on only a few occasions were the higher densities observed in the “poor” infectors.

The qualitative and quantitative infection of the mosquitoes infected on patients of either category, varies directly with the gametocyte density, although at any given density the qualitative infection arising from a feed on a “poor” infector will more likely be lower than that resulting from an application to a “good” infector of comparable density.

Although gametocyte densities in “good” infectors have tended to be slightly higher than in “poor” infectors, the most striking difference lies in the parity of the sexes in the “good” infectors, and deficiency of males in the “poor” infectors.

Although the data submitted abundantly establish these relationships, gametocyte density is not a reliable guide to the probable resulting qualitative infection of mosquitoes.

It is possible that varying proportions of susceptible and refractory mosquitoes in different lots affect the qualitative infection of any lot, particularly when the gametocyte density is low.

These observations also suggest that the gametocytes of “poor” infectors are inferior, perhaps in vitality, to those produced in “good” infectors.