Congenital plasmodium falciparum infection in a meso-endemic area of Uganda : molecular perspective

Abstract

Malaria remains a major public health concern especially among pregnant women and young children in sub-Saharan Africa. Few studies in Uganda have examined congenital malaria (CM) defined as presence of malaria parasites in blood within first 7 days of life. There is no recommendation on the most appropriate diagnostic method. Malaria rapid diagnostic tests (mRDTs) that target histidine-rich protein 2 (HRP2) are in use routinely in Uganda, however, Pfhrp2/3 gene deletions threaten their use. This study was designed to determine the proportion of congenital malaria and diagnostic performance of mRDT against nested PCR in Kasangati Health Centre IV. The mRDT was performed on venous blood of mothers and cord blood samples of neonates at birth; positive samples were analysed using microscopy to quantify parasitemia. The red blood cells from PRIME study that had been archived were used to extract genomic DNA. The 18S rRNA targeted nPCR run on 126 mother-baby paired DNA samples. The Pfhrp2/3 gene amplification using nPCR was run on all 7 positive mRDT, 33 positive 18S rRNA (4 positive for both mRDT and nPCR) samples. Of the 126 mother-baby paired blood samples which were examined by mRDT in PRIME study, 6/126 (4.8%) mothers and 1/126 (0.8%) neonates’ samples were positive for P. falciparum infection. A total of 33/252 (13.1%) samples were amplified for P. falciparum by 18S rRNA targeted nPCR including 4/7(57.1%) mRDT samples, out of which 15/126 (11.9%) and 18/126 (14.3%) were positive for neonates and mothers respectively. A total of 18/33 (54.5%) mother-baby paired samples had P. falciparum infection by 18S rRNA targeted nPCR. Only 36 samples of positive mRDT /or 18S rRNA targeted nPCR were included in Pfhrp2 and Pfhrp3 gene amplifications where by 1/36 (2.8%) amplified only Pfhrp2 gene, 6/36 (16.7%) amplified only Pfhrp3 gene while 2/36 (5.6%) amplified both Pfhrp2 and Pfhrp3 genes. This study showed existence of transplacental transmission of P. falciparum that leads to congenital malaria. Also both Pfhrp2 and Pfhrp3 genes were deleted in this meso-endemic study area and can potentially influence sensitivity of mRDT method as in other countries.