Résumé
Submicroscopic Plasmodium falciparum gametocytemia (<5,000
gametocytes/mL) is common and may result in mosquito infection. We
assessed the relation between gametocyte density and mosquito infection
under experimental and field conditions using real-time quantitative
nucleic acid sequence-based amplification (QT-NASBA) for gametocyte
quantification. Serial dilutions of NF54 P. falciparum gametocytes showed
a positive association between gametocyte density and the proportion of
infected mosquitoes (beta=6.1; 95% confidence interval [CI], 2.7-9.6;
P=0.001). Successful infection became unlikely below an estimated density
of 250-300 gametocytes/mL. In the field, blood samples of 100 naturally
infected children showed a positive association between gametocyte density
and oocyst counts in mosquitoes (beta=0.38; 95% CI, 0.14-0.61; P=0.002).
The relative contribution to malaria transmission was similar for carriers
with submicroscopic and microscopic gametocytemia. Our results show that
transmission occurs efficiently at submicroscopic gametocyte densities and
that carriers harboring submicroscopic gametocytemia constitute a
considerable proportion of the human infectious reservoir.