Observations on the infectiousness of gametocytes in hyperendemic malaria

There is a correlation between the probability of a mosquito's becoming infected and the gametocyte density of the carrier, when densities are broadly grouped. A small series of experiments in the hyperendemic zone of S. W. Nigeria are reported in which A. gambiae gambiae were allowed to feed on children carrying different densities of P. falciparum gametocytes. In the community from which these subjects came the average density of gametocytes was low, approximately of all gametocyte carriers showing less than 100 per c.mm., and more than 100 per c.mm. Of mosquitoes feeding once on the first group (less than 100 gametocytes per c.mm.) 5 per cent. could become infected if they survived long enough for completion of the extrinsic cycle, while of mosquitoes feeding on the second group (more than 100 per c.mm.) 50 per cent. could become infected. Other workers have found a higher proportion infected in the first group. These figures are used in a hypothetical example to calculate the proportion of all A. gambiae feeding on the population at one moment which could become infected.