What is it about?
Plasmodium vivax, a malaria parasite that can stay dormant in the liver and originate relapses within months after a single mosquito inoculation, causes 76% of the malaria burden in Latin America. Pregnant women are ineligible for primaquine, the only currently available drug that is able to prevent P. vivax relapses. Here we apply a mathematical model to real-life data from Brazil’s main malaria transmission hotspot and estimate that, once infected with P. vivax, 23% of the pregnant women will have one or more vivax malaria recurrences over the next 12 weeks. Significantly, 86% of these early P. vivax recurrences are attributable to relapses or late recrudescences, which could be prevented by primaquine administration. Repeated vivax malaria infections during pregnancy are associated with adverse effects on maternal and neonatal health. We show that weekly chloroquine chemoprophylaxis extending over 4 to 12 weeks, starting after the first vivax malaria episode diagnosed in pregnancy, might reduce the risk of P. vivax recurrences over the next 12 months by 20% to 65%, and should be investigated as a measure to lower the burden of repeated vivax malaria during pregnancy.
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Why is it important?
More widely prescribing post-treatment prophylaxis with weekly chloroquine in the management of vivax malaria in pregnancy may minimize the consequences of primaquine ineligibility, by preventing parasite recurrences and averting adverse effects on mothers' and neonates' health.
Perspectives
We quantified P. vivax recurrences in pregnant and non-pregnant patients using survival anazlysis accounting for competing risk. The model accounts for competing risks since, in endemic settings, relapses and late recrudescences (that may be at least partially prevented by primaquine) and new infections (that are not affected by primaquine use) all contribute to recurrences.
Rodrigo M. Corder
Universidade de Sao Paulo Campus da Capital
Read the Original
This page is a summary of: Quantifying and preventing Plasmodium vivax recurrences in primaquine-untreated pregnant women: An observational and modeling study in Brazil, PLoS Neglected Tropical Diseases, July 2020, PLOS,
DOI: 10.1371/journal.pntd.0008526.
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Resources
Low-level Plasmodium vivax exposure, maternal antibodies, and anemia in early childhood: Population-based birth cohort study in Amazonian Brazil
Plasmodium vivax malaria causes frequent hospital admissions of infants and toddlers in areas of intense transmission in the Asia-Pacific region, often due to severe anemia, but its epidemiology and burden have been understudied in children from other endemic settings. Here we characterize the cumulative impact of P. vivax infections in infants and toddlers exposed to relatively low levels of malaria transmission in the Brazilian Amazon. We have previously shown that vivax malaria in pregnancy is associated with increased risk of maternal anemia and impaired fetal growth in this population. Now we show that the adverse effects of malaria extend to early childhood. Children born to mothers who had one or more infections during pregnancy are at an elevated risk of P. vivax malaria in their early life, although the transfer of maternal antibodies to the fetus may provide some short-term protection. Children who are repeatedly infected with P. vivax since birth are more likely to be anemic at the age of 2 years. These findings further challenge the traditional view of vivax malaria as a relatively benign infection in pregnancy and early childhood in the Amazon.
The Hidden Burden of Plasmodium vivax Malaria in Pregnancy in the Amazon: An Observational Study in Northwestern Brazil
We measured the prevalence of malaria in pregnancy and estimated its impact on birth weight and length and maternal hemoglobin in 1,180 women from Juruá Valley, the main malaria hotspot in Brazil. Antenatal malaria episodes, 74.6% of them due to Plasmodium vivax, were microscopically diagnosed in 8.0% of the women and were associated with an average reduction in birth weight z-scores of 0.35 (95% confidence interval [CI] = 0.14–0.57) and in birth length z-scores of 0.31 (95% CI = 0.08–0.54), compared with malaria-free pregnancies. Affected mothers had a mean decrease in hemoglobin concentration at delivery of 0.33 g/100 mL (95% CI = 0.05–0.62 g/100 mL); 51.6% were anemic. The timing and frequency of antenatal infections influenced pregnancy outcomes and first- or second-trimester infections were not associated with decreased birth weight and length and maternal hemoglobin at delivery. Although repeated antenatal vivax infections were associated with poorer birth outcomes, even a single vivax malaria episode was associated with a significant reduction in birth weight and length and maternal hemoglobin. Overall, 7.5% women had the parasite’s DNA found in peripheral blood at delivery. Most (83.1%) of these 89 perinatal infections were due to P. vivax and only 7.9% of them progressed to symptomatic disease after delivery. Plasmodium vivax and Plasmodium falciparum DNA was found in 0.6% and 0.3% of 637 cord blood samples examined, respectively, but only one newborn developed clinical neonatal malaria. Our results further challenge the notion that vivax malaria is relatively benign during pregnancy and call for better strategies for its prevention.
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