Substantial contribution of submicroscopical Plasmodium falciparum gametocyte carriage to the infectious reservoir in an area of seasonal transmission.
BACKGROUND
Man to mosquito transmission of malaria depends on the presence of the sexual stage parasites, gametocytes, that often circulate at low densities. Gametocyte densities below the microscopical threshold of detection may be sufficient to infect mosquitoes but the importance of submicroscopical gametocyte carriage in different transmission settings is unknown.


RESULTS
Membrane feeding experiments were carried out on 80 children below 14 years of age at the end of the wet season in an area of seasonal malaria transmission in Burkina Faso. Gametocytes were quantified by microscopy and by Pfs25-based quantitative nucleic acid sequence-based amplification assay (QT-NASBA). The children's infectiousness was determined by membrane feeding experiments in which a venous blood sample was offered to locally reared Anopheles mosquitoes. Gametocytes were detected in 30.0% (24/80) of the children by microscopy compared to 91.6% (65/71) by QT-NASBA (p<0.001). We observed a strong association between QT-NASBA gametocyte density and infection rates (p = 0.007). Children with microscopically detectable gametocytes were more likely to be infectious (68.2% compared to 31.7% of carriers of submicroscopical gametocytes, p = 0.001), and on average infected more mosquitoes (13.2% compared to 2.3%, p<0.001). However, because of the high prevalence of submicroscopical gametocyte carriage in the study population, carriers of sub-microscopical gametocytes were responsible for 24.2% of the malaria transmission in this population.


CONCLUSIONS
Submicroscopical gametocyte carriage is common in an area of seasonal transmission in Burkina Faso and contributes substantially to the human infectious reservoir. Submicroscopical gametocyte carriage should therefore be considered when implementing interventions that aim to reduce malaria transmission.
Ouédraogo
André Lin
AL
Department of Biomedical Sciences, Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso. andrelin.cnrfp@fasonet.bf
Bousema
Teun
T
Schneider
Petra
P
de Vlas
Sake J
SJ
Ilboudo-Sanogo
Edith
E
Cuzin-Ouattara
Nadine
N
Nébié
Issa
I
Roeffen
Will
W
Verhave
Jan Peter
JP
Luty
Adrian J F
AJ
Sauerwein
Robert
R
D000293:Adolescent; D000818:Animals; D000852:Anopheles / Q000469:parasitology; D002050:Burkina Faso; D002648:Child; D002675:Child, Preschool; D004197:Disease Reservoirs / Q000469:parasitology*; D005247:Feeding Behavior; D005260:Female; D005854:Germ Cells / Q000166:cytology* / Q000378:metabolism; D006801:Humans; D007303:Insect Vectors / Q000469:parasitology*; D016778:Malaria, Falciparum / Q000469:parasitology* / Q000635:transmission*; D008297:Male; D008567:Membranes, Artificial; D010963:Plasmodium falciparum / Q000166:cytology*; D012621:Seasons; D021161:Self-Sustained Sequence Replication
D008567:Membranes, Artificial