The burden of malaria during pregnancy in Monrovia, Liberia after the Ebola outbreak

Continued monitoring of malaria in pregnancy is lacking in Liberia. There is a dearth of a robust malaria surveillance system. This situation was aggravated by the deviation of resources to monitor the Ebola epidemics.  

Interruption of malaria control during the Ebola epidemic posed the risk to promote changes in susceptibility to malaria. These potential changes represent a reason for closely monitoring of malaria trends. Such population-based approaches require a logistically complex collection of biological samples. In contrast, pregnant women are a group of relatively easy access through ANC.

In a context such as Liberia, where surveys such as MIS cannot be easily conducted, having timely first-hand prevalence data from pregnant women might have an added value as a proxy to prevalence rates of malaria at community-level.  Knowledge of the distribution of antimalarial resistances would be critical to informing the Liberian Ministry of Health and Social Welfare on the expected efficacy of IPTp. Monitoring molecular markers of resistance (e.g. Kelch13) in parasites isolated from pregnant women in their first visit to ANC could help provide estimates of resistance to Artemisinin-based first-line treatment. In particular, for post-Ebola Liberia, the continued vigilance of the malaria burden will be critical to assess whether there is an increasing trend of malaria incidence in urban areas and whether this trend is followed by an increase in the frequency of severe malaria syndromes.  

Understanding the determinants of changing trends in malaria prevalence, as well as the timescales over which antimalarial immunity is gained and lost, is a priority to prevent reinfection and resurgence of malaria infections.

In this regard, this study aims to assess malaria prevalence in pregnant women attending ANC, under the assumption that molecular testing and pregnancy-specific serology may be a more effective sentinel-based approach to estimate the burden of malaria than conventional microscopy and RDT. Several pieces of evidence point to IgG against VAR2CSA (the parasite antigen that mediates sequestration of P. falciparum in the placenta) as a marker of cumulative exposure to P. falciparum during pregnancy that can provide estimates of malaria transmission (Mayor et al., 2015).

ISGlobal has developed an approach to monitor malaria burden which is based on the pathophysiology of malaria in pregnancy. Malaria in pregnancy is characterized by a massive accumulation of P. falciparum-infected erythrocytes in the intervillous space of the placenta. Knowledge of the parasite antigen mediating this sequestration (VAR2CSA) has provided us with the principle to develop a pregnancy-serological tool for the assessment of malaria transmission. Antibodies against VAR2CSA are developed after exposure to placental parasites in a parity-dependent manner (i.e., increase with exposure during successive pregnancies) and are affected by variables that influence the risk of exposure to P. falciparum such as season, proximity to the river, use of IPTp or ITN. Serological parameters with parity stratification may be used to determine recent and past changes in transmission intensity in women pregnant for the first time and in those with more than a previous pregnancy.

This study is proposed by a team of investigators affiliated with Saint Joseph’s Catholic Hospital (Liberia), Fundación Juan Ciudad (FJC) (Spain), ISGlobal (Spain), and CISM (Mozambique).   

Overall, this study is expected to provide baseline information on the prevalence of malaria in an urban post-Ebola Liberian context and to contribute to shift the current paradigm of pregnant women as a vulnerable group to that of a population with the potential to serve for the real-time monitoring of malaria transmission utilizing molecular and serological tools with enough sensitivity to guide malaria control activities.

Observational mixed-methods cross-sectional study.

EDCTP Grants

Measurement of Transmission
Vulnerable Populations

Aug 2016 — Jul 2017

$271,329

Liberia

Malaria Molecular Surveillance (MMS)