Impact of Submicroscopic Plasmodium falciparum Parasitaemia on Maternal Anaemia and Low Birth Weight in Blue Nile State, Sudan

Abstract

The aim of the present study was to investigate the prevalence of submicroscopic infections and to assess its impact on maternal anaemia and low birth weight. A cross-sectional study was carried out with 1149 consented pregnant women who delivered at 3 main hospitals in the Blue Nile State, between January 2012 and December 2015. From a matched maternal peripheral, placental maternal side, and cord blood sample, blood films and dried spots were prepared for microscopic examination and nested polymerase chain reaction (n-PCR), respectively. 107 out of 447 negative blood films were found to have submicroscopic infection detected using n-PCR in any of the three compartments. Placental samples had a significantly higher prevalence (142) of submicroscopic infections compared with the peripheral (6.5%) and cord (8.1%) samples. The mean (SD) of the maternal haemoglobin (Hb) was significantly lower in cases with submicroscopic parasitaemia (10.9 (0.8) vs. 12.1 (0.7) g/dl, P<0.001) compared with those who had no submicroscopic parasitaemia. Submicroscopic malaria infection was associated with anaemia (OR 19.7, (95% CI, 10.3–37.8)). Thirty-eight babies born to women with submicroscopic infections were low birth weight (LBW) and was significantly lower in submicroscopic parasitaemia (2.663 (0.235) vs. 2.926 (0.341) kg, P<0.001). Submicroscopic malaria infection was associated with LBW (OR = 2.7, (95% CI, 1.2–5.6)). There is a high incidence of submicroscopic infections in any of the three compartments regardless of age or parity. Submicroscopic infection is a risk of maternal anaemia and low birth weight in women in this area of high seasonal malaria transmission.

Factors associated with sub-microscopic placental malaria and its association with adverse pregnancy outcomes among HIV-negative women in Dar es Salaam, Tanzania: a cohort study

“…Previous studies have pointed out that pregnant women often have low parasite densities, and the use of highly sensitive diagnostic methods such a DNA polymerase chain reaction (DNA PCR) (referred to as sub-microscopic placental malaria) has been recommended to enhance detection of placental malaria [6]. Sub-microscopic MiP remains common in most African countries including Tanzania [8][9][10][11], even though there was a 41% reduction of the malaria incidence rate in sub-Saharan Africa for the period of 2000-2015 [12]. The decreasing proportion of individuals presenting with clinical malaria infection over time has been linked with the scale-up of effective malaria interventions including insecticide-treated nets, effective case management, and indoor residual spraying [13].…”

“…Peripheral sub-microscopic malaria is strongly associated with placental malaria and low maternal hemoglobin levels [14,15], but there are contradictory findings about the association between placental malaria and adverse pregnancy outcomes [11,16,17]. Cottrell et al [16] found that sub-microscopic malaria infection during early pregnancy was associated with adverse pregnancy outcomes, whereas infection detected at delivery in the placenta and peripheral blood sample was not.…”

Global & Temporal Patterns of Submicroscopic Plasmodium falciparum Malaria Infection

“…7 Such "submicroscopic" infections are present across a range of different settings and populations 5,9-8 11 . Although rarely causative of severe symptoms, they have been associated with a number of adverse 9 outcomes during pregnancy 12,13 , as well as mild anaemia 14 and other symptoms (vomiting, jaundice 10 etc.) in children under 10 15 .…”

“…There was no evidence of systematic differences in the PCR and 11 microscopy methodologies in different transmission archetypes (Supp Fig.6) and the observed results 12 were robust to the choice of High/Low threshold (Supp Fig.7). 13 Integrating these results with estimates of comparative submicroscopic infectivity to mosquitoes, we 14 estimate that in transmission settings characterised by historically low levels of transmission, 15 submicroscopically infected individuals could account for 17.5% to 68.0% of onwards transmission in 16 low prevalence settings (defined as <= 5% survey prevalence by PCR), depending on the assumption 17 surrounding the comparative infectivity of microscopically detectable and submicroscopic infections 18 (Fig.7C). By contrast, our results suggest the contribution of the submicroscopic reservoir to 19 transmission is less important in settings where transmission has only recently declined (Fig.7B) 20 although their contribution is not irrelevant, ranging from 7.8% to 46.0% depending on the assumed 21 comparative infectivity.…”

Sulfadoxine-pyrimethamine parasitological efficacy against Plasmodium falciparum among pregnant women and molecular markers of resistance in Zambia: an observational cohort study

“…The prevalence of submicroscopic malaria infection among pregnant women in the current study was considerable. Other studies have found wide spread submicroscopic malaria infections [ 47 – 49 ]. Many asymptomatic infections are submicroscopic and can only be detected by molecular methods.…”