Validation of real-time PCR assays for detecting Plasmodium and Babesia DNA species in blood samples

Abstract

Malaria and babesiosis are global health threats affecting humans, wildlife, and domestic animals, particularly in Africa, the Americas, and Europe. Malaria can lead to severe outcomes, while babesiosis usually resembles a mild illness but can be severe and fatal in individuals with weakened immune systems. Swift, accurate detection of these parasites is crucial for treatment and control. We evaluated a real-time PCR assay for diagnosing five Plasmodium and three Babesia species from blood samples, assessing its sensitivity, specificity, and analytical performance by analyzing 46 malaria-positive and 32 Babesia spp-positive samples diagnosed through microscopy. The limit of detection for Plasmodium species ranged from 30 to 0.0003 copies/µL. For mixed infections, it was 0.3 copies/µL for P. falciparum/P. vivax and 3 copies/µL for P. malariae/P. knowlesi. Babesia species had a detection limit of 0.2 copies/µL. No cross-reactivity was observed among 64 DNA samples from various microorganisms. The assay showed good sensitivity, detecting Plasmodium and Babesia species with 100 % accuracy overall, except for P. falciparum (97.7 %) and B. microti (12.5 %). The low sensitivity of detecting B. microti was attributed to limitations in microscopy for species identification. This technique heavily relies on the proficiency of the examiner, as species within the genus cannot be distinguished under a microscope. Additionally, Babesia can be confused with the early trophozoite stage (ring forms) of Plasmodium parasites. The findings support multiplex qPCR's diagnostic superiority over the gold standard, despite higher costs. It offers enhanced sensitivity, specificity, and detects mixed infections, crucial for effective monitoring and diagnosis of malaria and babesiosis in endemic regions with significant public health challenges.