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Gravidity and malaria trends interact to modify P. falciparum densities and detectability in pregnancy: a 3-year prospective multi-site observational study

Abstract : Background Low-density Plasmodium falciparum infections prevail in low transmission settings, where immunity is expected to be minimal, suggesting an immune-independent effect on parasite densities. We aimed to describe parasite densities in pregnancy, and determine how gravidity and antibody-mediated immunity affect these, during a period of declining malaria transmission in southern Mozambique. Methods We documented P. falciparum infections at first antenatal care visits ( n = 6471) between November 2016 and October 2019 in Ilha Josina (high-to-moderate transmission area), Manhiça (low transmission area), and Magude (pre-elimination area). Two-way interactions in mixed-effects regression models were used to assess gravidity-dependent differences in quantitative PCR-determined P. falciparum positivity rates ( Pf PR qPCR ) and densities, in the relative proportion of detectable infections (pDi) with current diagnostic tests (≥ 100 parasites/μL) and in antimalarial antibodies. Results Pf PR qPCR declined from 28 to 13% in Ilha Josina and from 5–7 to 2% in Magude and Manhiça. In primigravidae, pDi was highest in Ilha Josina at the first study year ( p = 0.048), which declined with falling Pf PR qPCR (relative change/year: 0.41, 95% CI [0.08; 0.73], p = 0.029), with no differences in antibody levels. Higher parasite densities in primigravidae from Ilha Josina during the first year were accompanied by a larger reduction of maternal hemoglobin levels (− 1.60, 95% CI [− 2.49; − 0.72; p < 0.001), than in Magude (− 0.76, 95% CI [− 1.51; − 0.01]; p = 0.047) and Manhiça (− 0.44, 95% CI [− 0.99; 0.10; p = 0.112). In contrast, multigravidae during the transmission peak in Ilha Josina carried the lowest pDi ( p = 0.049). As Pf PR qPCR declined, geometric mean of parasite densities increased (4.63, 95% CI [1.28; 16.82], p = 0.020), and antibody levels declined among secundigravidae from Ilha Josina. Conclusions The proportion of detectable and clinically relevant infections is the highest in primigravid women from high-to-moderate transmission settings and decreases with declining malaria. In contrast, the falling malaria trends are accompanied by increased parasite densities and reduced humoral immunity among secundigravidae. Factors other than acquired immunity thus emerge as potentially important for producing less detectable infections among primigravidae during marked declines in malaria transmission.
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https://hal-cnrs.archives-ouvertes.fr/hal-03858900
Contributor : Benoit Gamain Connect in order to contact the contributor
Submitted on : Thursday, November 17, 2022 - 10:53:13 PM
Last modification on : Saturday, November 19, 2022 - 3:09:48 AM

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Glória Matambisso, Nanna Brokhattingen, Sónia Maculuve, Pau Cisteró, Henriques Mbeve, et al.. Gravidity and malaria trends interact to modify P. falciparum densities and detectability in pregnancy: a 3-year prospective multi-site observational study. BMC Medicine, 2022, 20 (1), pp.396. ⟨10.1186/s12916-022-02597-6⟩. ⟨hal-03858900⟩

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