Molecular monitoring of the diversity of human pathogenic malaria species in blood donations on Bioko Island, Equatorial Guinea

Abstract

BackgroundMalaria can be transmitted by blood transfusion from human to human and it is responsible for the majority of transfusion-transmitted infectious diseases worldwide. In sub-Saharan Africa, it had been estimated that almost a quarter of blood donations contain malaria parasites. Since rapid diagnostic tests and thick blood smear microscopy lack sensitivity for low density parasitaemia, particularly in asymptomatic adults, the most reliable method to assess the problem of transfusion-transmitted malaria are nucleic acid-based molecular approaches such as quantitative polymerase chain reaction. The study was undertaken to determine the prevalence of sub-microscopic malaria parasite infection among blood donors in Malabo, Equatorial Guinea.MethodsBetween July and August 2017, a total of 200 individual blood samples from blood donors at the Malabo Blood Bank were collected and screened by rapid diagnostic tests and thick blood smear microscopy. Retrospectively, the same samples were analysed for the presence of undetected, low-density malaria parasites using quantitative polymerase chain reaction.ResultsIn comparison to 6.5% (13/200) by rapid diagnostic test and 2.0% (4/200) by microscopy, the proportion of Plasmodium falciparum positive blood donations analysed by quantitative polymerase chain reaction was significantly higher (26%, 52/200). Densities of P. falciparum positive blood donations were ranging from 0.06 to 3707.0 parasites/µL with 79.6% below 100 parasites/µL and therefore not detectable by non-molecular malaria diagnostic tests. qPCR based species identification revealed that P. falciparum was the dominating species responsible for 88.1% (52/59) of positive blood donations, followed by Plasmodium malariae (15.3%, 9/59) and Plasmodium ovale (3.4%, 2/59).ConclusionsThis study confirms that in malaria endemic settings, sub-patent malaria infections among blood donors are prevalent. In blood collected from healthy donors living in Malabo, P. falciparum, P. malariae and P. ovale parasites were identified. Currently widely used malaria diagnostic tools have missed more than 75% of P. falciparum containing blood donations, demonstrating the value of quantitative polymerase chain reaction to reliably detect low density P. falciparum infections. Since the availability of molecular diagnostic methods in malaria endemic countries is still limited, the blood recipients living in malaria endemic countries should be treated following WHO recommendations.Electronic supplementary materialThe online version of this article (10.1186/s12936-019-2639-8) contains supplementary material, which is available to authorized users.

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“…Plasmodium falciparum ( P. falciparum ), the causative agent of malaria tropica, is the most dangerous of the six human‐pathogenic Plasmodium species and responsible for the vast majority of deaths. [ 1,2 ] To decrease the burden in endemic areas, malaria researchers worldwide strive to identify and test drug targets as well as vaccine candidates against P. falciparum and other Plasmodium species. Multiple vaccine candidates are in clinical development at the moment.…”

Polymorphic markers for identification of parasite population in Plasmodium malariae

“…These chronic P. malariae infections can occasionally cause anemia and nephrotic syndrome (4,(6)(7)(8). Use of molecular techniques such as qPCR has enabled more sensitive detection of parasite carriage compared to microscopy (3,9). Previous studies conducted in Cameroon (10) and Equatorial Guinea (9) using qPCR based species identification revealed that P. falciparum was the dominating species responsible for over 80.0% of malaria positive cases, followed by P. malariae (≥12.0%).…”