Real-time PCR diagnosis of Plasmodium vivax among blood donors

BACKGROUND: When selecting blood donors in transfusion centres, one important problem is to identify, during screening, individuals with infectious diseases that can be transmitted by blood, such as malaria, especially when the parasite densities are very low. This problem is particularly severe in endemic areas, such as the Brazilian Amazon. In the present study, molecular diagnostic (real-time PCR) of Plasmodium vivax was used to identify blood donors infected with malaria parasites. METHODS: Samples from 595 blood donors were collected in seven haemotherapy centres in northern Brazil located in areas at risk for malaria transmission, and the analyses were performed by real-time PCR with TaqMan probes on 7500 Real-Time PCR Systems, to genotype the mitochondrial DNA region specific to P. vivax. The experiment was designed for hybridization of the cytochrome c oxidase genes of the mitochondrial genome (GenBank GI63022502). The serological data were obtained using enzyme-linked immunosorbent assay - ELISA (Anti-HIV, Anti-HTLV I-II; Anti-HVC, HBsAg, Anti-HBc, Chagas disease) and VDRL (Syphilis) from the Blood Bank System of the Haematology and Haemotherapy Centre of Pará. RESULTS: The assay identified eight individuals in the sample (1.34%) infected with P. vivax at the time of blood donation. This percentage was higher than the altered serological results (reactive or inconclusive) of the prevalence of anti-HIV (0.67%), anti-hepatitis C virus (0.34%), anti-hepatitis B surface antigen (0.67%), anti-human T-lymphotropic virus I/II (1.18%), anti-Chagas disease (0.17%) and syphilis (VDRL) (0.50%), but not higher than anti-hepatitis B core antigen antibodies (4.37%). This result indicates the need to use more sensitive methods of diagnosing malaria in blood banks. CONCLUSION: The real-time PCR with TaqMan probes enabled the identification of P. vivax in a high proportion of clinically healthy donors, highlighting the potential risk for transfusion-transmitted malaria. Additionally, this molecular diagnostic tool can be adopted as a new laboratory screening method in haemotherapy centres, especially in malaria-endemic areas.