# Undetected Plasmodium malariae and P. ovale infections in HRP2 RDT-positive children with uncomplicated malaria in Nanoro, Burkina Faso

## TL;DR

This study found that some malaria cases in children in Burkina Faso are caused by non-falciparum species that are missed by common rapid diagnostic tests.

## Contribution

The study highlights the underestimation of non-falciparum malaria species due to reliance on HRP2-based RDTs.

## Key findings

- Four non-falciparum malaria cases were detected via microscopy among HRP2 RDT-positive children.
- Sub-patent infections with P. malariae and P. ovale were found in 6 and 5 cases, respectively.
- Mixed infections had lower parasite densities than P. falciparum mono-infections.

## Abstract

The widespread use of histidine-rich protein 2 (HPR2)-based rapid diagnostic tests (RDTs), specific to Plasmodium falciparum in endemic areas may underestimate the weight of minor species such as P. malariae and P. ovale in malaria transmission. This study aimed to determine the extent of undetected P. malariae and P. ovale infections in children with positive diagnosis of uncomplicated malaria based on HRP2 RDT in the Nanoro health district, Burkina Faso.

Children <5 yrs with uncomplicated malaria confirmed by HRP2 RDT were recruited from July 2021 to June 2022 in five peripheral health facilities of the Nanoro health district. Blood samples were collected from finger prick for malaria species identification by microscopy and nested PCR. The prevalence of P. malariae, P. ovale, and mixed infections was estimated as the ratio of positive cases over the total samples analysed. Binomial generalised linear models were used to assess the effect of age and sex on the positivity rate of mixed infections.

Over the study period, 207 children with uncomplicated malaria who tested positive for the HRP2 antigen were included. Microscopy detected 4 non-falciparum cases: 3 P. malariae and 1 P. ovale. In addition to these patent cases, sub-patent infection with P. ovale and P. malariae were detected in 6 and 5 cases, respectively. Mixed infections with non-falciparum species exhibited lower parasite densities than mono-infections with P. falciparum alone. There was no effect of gender or age on the mixed infection positivity rate (X2=0.16, p=0.683).

The widespread use of HPR2-based RDTs underestimate the burden of non-falciparum species. In the context of eliminating malaria, new diagnostic tools allowing the detection of Plasmodium species other than P. falciparum must be deployed.