Prevalence of and risk factors for microscopic and submicroscopic malaria infections in pregnancy: a systematic review and meta-analysis

Addressing low-density malaria infections in India and other endemic part of the world-the opportune time?

Shifting from high- to low-malaria transmission accompanies a higher proportion of asymptomatic low-density malaria infections (LDMI). Currently, several endemic countries, such as India, are experiencing this shift as it is striving to eliminate malaria. LDMI is a complex concept for which there are several important questions yet unanswered on its natural history, infectiousness, epidemiology, and pathological and clinical impact. India is on the right path to eliminating malaria, but it is facing the LDMI problem. A brief discussion on the concept and definitions of LDMI is beforehand presented. Also, an exhaustive review and critical analysis of the existing literature on LDMI in malaria-endemic areas, including India, are included in this review. Finally, we opine that addressing LDMI in India is ethically and pragmatically achievable, and a pool of sine qua non conditions is required to efficiently and sustainably eliminate malaria.

Imported malaria in pregnancy in Europe: A systematic review of the literature of the last 25 years

BACKGROUND

Malaria during pregnancy is associated with a greater risk of complications for the mother and fetus. The aim of the study is to analyze the features of imported cases of malaria in pregnant women in Europe and evaluate which factors are associated with a non-favourable outcome.

METHODS

A computerized search of the literature was performed combining the terms plasmod*, malaria, pregnan*, maternal, gravid, parturient, expectant, and congenital, from January 1997 to July 2023.

RESULTS

28 articles reporting 57 cases of malaria in pregnant women immigrant in non-endemic areas were included. The patients mainly came from Sub-Saharan Africa. There were 10 asymptomatic cases, while the predominant clinical syndrome among the symptomatic women was fever associated with anaemia. The median latency period from permanence in endemic areas and diagnosis in European countries was 180 days (IQR 15-730). Pregnancy outcomes were favourable in 35 cases (61 %): all term pregnancies, no low-birth-weight newborns. There were 4 abortions; 1 child was delivered pre-term; 7 babies were reported to have a low birth weight; 10 cases of congenital malaria were documented. P. falciparum was found with a higher frequency in women with a favourable outcome, while P. vivax was, in all cases, associated with a worse prognosis.

CONCLUSIONS

Diagnosis of malaria in pregnant woman in non-endemic countries may be challenging and a delay in diagnosis may lead to an adverse outcome. Screening for malaria should be performed in pregnant women from endemic areas, especially if they present anaemia or fever.

Revealing invisible cell phenotypes with conditional generative modeling

Biological sciences, drug discovery and medicine rely heavily on cell phenotype perturbation and microscope observation. However, most cellular phenotypic changes are subtle and thus hidden from us by natural cell variability: two cells in the same condition already look different. In this study, we show that conditional generative models can be used to transform an image of cells from any one condition to another, thus canceling cell variability. We visually and quantitatively validate that the principle of synthetic cell perturbation works on discernible cases. We then illustrate its effectiveness in displaying otherwise invisible cell phenotypes triggered by blood cells under parasite infection, or by the presence of a disease-causing pathological mutation in differentiated neurons derived from iPSCs, or by low concentration drug treatments. The proposed approach, easy to use and robust, opens the door to more accessible discovery of biological and disease biomarkers.

Micro-heterogeneity of transmission shapes the submicroscopic malaria reservoir in coastal Tanzania

Background

Asymptomatic malaria may be patent (visible by microscopy) and detectable by rapid malaria diagnostic tests (RDTs), or it may be submicroscopic and only detectable by polymerase chain reaction (PCR).

Methods

To characterize the submicroscopic reservoir in an area of declining malaria transmission, asymptomatic persons >5 years of age in Bagamoyo District, Tanzania, were screened using RDT, microscopy, and PCR. We investigated the size of the submicroscopic reservoir across villages, determined factors associated with submicroscopic parasitemia, and assessed the natural history of submicroscopic malaria over four weeks.

Results

Among 6,076 participants, Plasmodium falciparum prevalence by RDT, microscopy, and PCR was 9%, 9%, and 28%, respectively, with roughly two-thirds of PCR-positive individuals harboring submicroscopic infection. Adult status, female gender, dry season months, screened windows, and bednet use were associated with submicroscopic carriage. Among 15 villages encompassing 80% of participants, the proportion of submicroscopic carriers increased with decreasing village-level malaria prevalence. Over four weeks, 23% (61/266) of submicroscopic carriers became RDT-positive and were treated, with half exhibiting symptoms. This occurred more frequently in villages with higher malaria prevalence.

Conclusions

Micro-heterogeneity in transmission impacts the size of the submicroscopic reservoir and the likelihood of submicroscopic carriers developing patent malaria in coastal Tanzania.

The question of the early diagnosis of asymptomatic and subpatent malaria in pregnancy: Implications for diagnostic tools in a malaria endemic area

Objectives

Malaria in pregnancy (MIP) is a major healthcare challenge in low-income countries with high malaria endemicity. Early but accurate diagnosis and appropriate treatment is the hallmark of preventing disease progression/adverse outcomes in the mother, foetus and neonates. We assessed the comparative diagnostic performance of Malaria Rapid Diagnostic Test (mRDT), microscopy and PCR for malaria diagnosis in pregnant women for early detection of asymptomatic malaria in pregnant women.

Study design

Five hundred and twenty Pregnant women attending study clinics within Ikene and Remo North LGAs with gestational age between 16 and 29 weeks, willing and consented; were enrolled into the study. Blood samples collected via venepuncture were screened for malaria using microscopy, mRDTs kits, and PCR techniques on their first visit (V1) and at delivery. The parasite positivity rates, sensitivity and specificity were calculated and compared for each technique using PCR as the standard. Data was entered into REDCap® online database and analysis done using Stata and MedCalc®.

Results and conclusions

Average age of enrolled women was 28.8 years and mean gestational age was 21.0 weeks. The parasite positivity rates were 4.3%, 8.8% and 25.0% for microscopy, mRDT and PCR at V1 and was 2.4%, 3.4% and 43.4% at delivery, respectively. Sensitivity for microscopy and mRDT was 11.2% and 30.3% respectively at V1, while specificity was 98.2% and 98.5%. At delivery, the sensitivity reduced to 1.6% and 4.9%; while specificity was 96.9% and 97.6% respectively. Only 2.3% cases correlated with all three diagnostic methods. Our data showed a decrease in sensitivity of the diagnostic methods as pregnancy progressed, which may be due to very low parasitaemia, but high specificity. Our study demonstrated a high rate of subpatent parasitaemia amongst pregnant women. This finding therefore raises the question of the effect of subpatent parasitaemia on the health of the mother and foetus.