Is Plasmodium vivax becoming more prevalent in parts of Nigeria? A molecular evaluation of the parasite from persons living in Ishielu, South-East Nigeria

Abstract

Plasmodium vivax, the leading cause of malaria in the vast majority of countries outside of Africa and the second most dominant cause of malaria globally, is fast becoming widespread and domiciled in Nigeria and other parts of sub-Saharan Africa. The objective of this cross-sectional survey conducted in Ishielu, a suburb of Abakaliki, southeastern Nigeria was to identify circulating Plasmodium species (with focus on P. falciparum and P. vivax species) in the population. A total of 120 venous blood samples (2-5 ml) of individuals in the community was examined microscopically; while thirty randomlyselected blood samples were used for polymerase-chain reaction (PCR) assays. Genomic DNA was isolated from the blood samples and species-specific nested PCRs targeting the 18S ribosomal ribonucleic acid (rRNA) gene were applied in detecting the presence of the target parasite species. Microscopy showed that 90% (108/120) of the blood samples were positive for parasitaemia and P. falciparum was the only Plasmodium species identified. Of the 30 selected blood samples assayed by PCR, the amplicon of 18S rRNA gene of the malaria parasite species was amplifiable in 80 % (24/30), combined vivax and falciparum positive cases were identified in three blood specimens and from microscopically negative slides. Mixed infections constituted 25% (6/24) while single infections with vivax and falciparum amounted to 42% (10/24) and 33% (8/24) respectively. These call for large-scale surveys of the target parasite species at community level by molecular PCR method for significant reduction of morbidity due to malaria.