Real-time PCR assay for discrimination of Plasmodium ovale curtisi and Plasmodium ovale wallikeri in the Ivory Coast and in the Comoros Islands

Abstract

Background: Plasmodium ovale is one of the five malaria species infecting humans. Recent data have shown that the name of this neglected species masks two distinct genotypes also called curtisi and wallikeri. Some authors show that these species could be sympatric. These two subspecies are not differentiated by microscopy techniques and malaria rapid diagnostic tests. This diagnostic defect is the result of low parasitaemia, antigenic polymorphism and absence of antibodies performance and requires the use of sequencing techniques. An accurate and easy discrimination detection method is necessary.

Methods: A new molecular assay was developed to easily identify the two genotypes of P. ovale. This tool allowed the study of 90 blood samples containing P. ovale, confirmed by molecular biology techniques, which were obtained from patients with imported malaria.

Results: The new marker was validated on well genotyped samples. The genotype of 90 P. ovale samples mainly imported from the Ivory Coast and the Comoros Islands was easily and quickly realized. The distribution of the two subspecies was described with a significant number of samples and showed that the two genotypes were present in the studied countries.

Conclusion: This work confirms the presence of the two species in the same country for the first time, in the Ivory Coast and the Comoros Islands. A better genotyping of P. ovale types may improve a better characterization of the clinical pathophysiology for each.

Figure 1

Real-time amplification plot with POC marker (A) and POW marker (B) of three samples of each, P. o. curtisi (black) and P. o. wallikeri (white). Water line is negative control (grey rhombus). Positive control (square). The X-axis: the cycle number and the Y-axis: the fluorescence arbitrary unit (FU). Detection was carried at 530 nm and at 560 nm for (A) and (B) respectively.