Changing Trends in P. falciparum Burden, Immunity, and Disease in Pregnancy
BACKGROUND: Prevention of reinfection and resurgence is an integral component of the goal to eradicate malaria. However, the adverse effects of malaria resurgences are not known. METHODS: We assessed the prevalence of Plasmodium falciparum infection among 1819 Mozambican women who delivered infants between 2003 and 2012. We used microscopic and histologic examination and a quantitative polymerase-chain-reaction (qPCR) assay, as well as flow-cytometric analysis of IgG antibody responses against two parasite lines.
RESULTS: Positive qPCR tests for P. falciparum decreased from 33% in 2003 to 2% in 2010 and increased to 6% in 2012, with antimalarial IgG antibody responses mirroring these trends. Parasite densities in peripheral blood on qPCR assay were higher in 2010-2012 (geometric mean [+/-SD], 409+/-1569 genomes per microliter) than in 2003-2005 (44+/-169 genomes per microliter, P=0.02), as were parasite densities in placental blood on histologic assessment (50+/-39% of infected erythrocytes vs. 4+/-6%, P<0.001). The malaria-associated reduction in maternal hemoglobin levels was larger in 2010-2012 (10.1+/-1.8 g per deciliter in infected women vs. 10.9+/-1.7 g per deciliter in uninfected women; mean difference, -0.82 g per deciliter; 95% confidence interval [CI], -1.39 to -0.25) than in 2003-2005 (10.5+/-1.1 g per deciliter vs. 10.6+/-1.5 g per deciliter; difference, -0.12 g per deciliter; 95% CI, -0.67 to 0.43), as was the reduction in birth weight (2863+/-440 g in women with past or chronic infections vs. 3070+/-482 g in uninfected women in 2010-2012; mean difference, -164.5 g; 95% CI, -289.7 to -39.4; and 2994+/-487 g vs. 3117+/-455 g in 2003-2005; difference, -44.8 g; 95% CI, -139.1 to 49.5).
CONCLUSIONS: Antimalarial antibodies were reduced and the adverse consequences of P. falciparum infections were increased in pregnant women after 5 years of a decline in the prevalence of malaria. (Funded by Malaria Eradication Scientific Alliance and others.).