Abstract
BackgroundThe estimates of risk of malaria in early childhood are imprecise given the current entomologic and parasitological tools. Thus, the utility of anti-Anopheles salivary gSG6-P1 peptide antibody responses in measuring exposure to Anopheles bites during early infancy has been assessed.MethodsAnti-gSG6-P1 IgG and IgM levels were evaluated in 133 infants (in Benin) at three (M3), six (M6), nine (M9) and 12 (M12) months of age. Specific IgG levels were also assessed in their respective umbilical cord blood (IUCB) and maternal blood (MPB).ResultsAt M3, 93.98 and 41.35% of infants had anti-gSG6-P1 IgG and IgM Ab, respectively. Specific median IgG and IgM levels gradually increased between M3 and M6 (p < 0.0001 and p < 0.001), M6–M9 (p < 0.0001 and p = 0.085) and M9–M12 (p = 0.002 and p = 0.03). These levels were positively associated with the Plasmodium falciparum infection intensity (p = 0.006 and 0.003), and inversely with the use of insecticide-treated bed nets (p = 0.003 and 0.3). Levels of specific IgG in the MPB were positively correlated to those in the IUCB (R = 0.73; p < 0.0001) and those at M3 (R = 0.34; p < 0.0001).ConclusionThe exposure level to Anopheles bites, and then the risk of malaria infection, can be evaluated in young infants by assessing anti-gSG6-P1 IgM and IgG responses before and after 6-months of age, respectively. This tool can be useful in epidemiological evaluation and surveillance of malaria risk during the first year of life.
Highlights
The estimates of risk of malaria in early childhood are imprecise given the current entomologic and parasitological tools
Evolution of specific immunoglobulin G (IgG) and IgM levels during the first year of life At month 3 (M3), levels of specific gambiae salivary gland protein-6 peptide 1 (gSG6-P1) IgG (Figure 1a) and IgM (Figure 1b) in the peripheral blood of infants were low [median IgG level (MIgG) = 0.383 and median IgM level (MIgM) = 0.228]. These levels of IgG and IgM gradually increased from M3-infants’ peripheral (M3) to M12 (MIgG = 0.721 and MIgM = 0.352), with intermediate values at M6 (MIgG = 0.527 and MIgM = 0.288) and M9 (MIgG = 0.646 and MIgM = 0.326)
The difference in the intensity of P. falciparum infection and the predicted entomological risk of exposure between any two consecutive age periods (M3–M6, M6–M9 and M9– M12) were not significant, unlike that observed for antigSG6-P1 Ab levels
Summary
The estimates of risk of malaria in early childhood are imprecise given the current entomologic and parasitological tools. In the absence of effective vaccines, malaria control and prevention strategies are primarily based on the widespread use of effective drugs and vector control by insecticide-treated bed nets (ITNs) and indoor residual sprays [1,2,3]. Newborn exposure to malaria has traditionally been assessed using entomological and parasitological methods These methods are labour-intensive and difficult to sustain especially in low transmission or exposure contexts [11, 12]. These methods are typically used at the community level measure and do not target the individual [13].
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