Estimated Plasmodium 18S ribosomal RNA prevalence in asymptomatic blood donors from three African countries.

Background and objectives: The World Health Organization (WHO) African Region accounts for 94% of malaria cases globally, with variability recognized within endemic regions. To determine the detection rate of Plasmodium RNA in blood donors resident in malaria-endemic areas, samples from three African countries were tested using a Plasmodium nucleic acid test.

Materials and methods: Whole blood (WB) samples collected from routine donors in Cameroon, Madagascar and Mali were shipped frozen to the United States. Samples were tested individually from WB lysates with the Procleix Plasmodium assay (transcription-mediated amplification [TMA]). Reactive samples were considered either repeat reactive or initial reactive only, depending on TMA-retest results. When available, matching plasma samples were tested for Plasmodium antibodies by enzyme immunoassay (EIA).

Results: Plasmodium repeat reactivity ranged from 41% (91/223 tested) in Cameroon to 12% (26/216) in Mali and 1% (3/249) in Madagascar. Initially reactive samples, where reactivity did not repeat, were identified from Cameroon (5/223; 2%) and Mali (2/216; 1%). The matched-plasma subgroup had EIA reactivity ranging from 86% (113/131 tested) in Cameroon to 59% (10/17) in Mali and 27% (68/248) in Madagascar.

Conclusion: Plasmodium ribosomal RNA (rRNA) detection and antibody rates varied greatly in the three countries studied. Detection of Plasmodium rRNA can provide an additional tool to address malaria risk in blood donors.