Observations on the periodicity of Plasmodium falciparum gametocytes in natural human infections

The circadian periodicity of Plasmodium falciparum gametocytes in peripheral blood was analysed in a group of children from an holoendemic community of north-eastern Tanzania. No periodicity was observed with asexual stage parasites. Gametocytes were shown to display a diurnal subperiodic pattern with a periodicity index of 31.8. Mathematical analysis of the data indicated that P. falciparum gametocytes tend to display periodicity with a peak (15:30–19:30 h) that do not coincide with the peak (00:30–03:30 h) biting activity of the local vector, Anopheles gambiae. We were thus able to show a P. falciparum gametocyte periodicity with a harmonic wave pattern, but its functional biological significance if any, is currently unknown.