Asymptomatic Malaria Cases and Plasmodium Species among BaAka Pygmies in Central Africa

TL;DR

This study found many asymptomatic malaria cases among BaAka Pygmies in Central Africa, showing that other Plasmodium species besides P. falciparum are also present.

Contribution

The study reveals the presence of multiple Plasmodium species and high asymptomatic malaria rates in a semi-nomadic tribe in Central Africa.

Findings

Asymptomatic malaria cases were twice as high in adults compared to children, suggesting age-related immunity.

Molecular tests identified P. malariae, P. ovale, and P. vivax in addition to P. falciparum among the BaAka Pygmies.

RT-PCR detected higher infection rates than rapid diagnostic tests, highlighting the need for more sensitive methods.

Abstract

Malaria is a significant health problem in Africa, primarily due to the Plasmodium falciparum species, but this is not the only etiological factor responsible for malaria on the continent. The goal of the present research was to describe asymptomatic malaria cases and to identify Plasmodium species responsible for malaria in the BaAka Pygmies, inhabitants of the Central African Republic (CAR). Screening was realised in the period of August–September 2021 among 308 people, including 74 children and 234 adults reporting to a healthcare facility in Monasao (southwest CAR), an area inhabited by a semi-nomadic tribe of BaAka Pygmies. The study consisted of two phases. Phase I, which was conducted in Africa, consisted of performing malaria rapid diagnostic tests (mRDTs), taking haemoglobin measurements and collecting blood samples onto Whatman FTA cards for molecular diagnostics. Phase II, which was conducted in Poland, involved molecular tests (RT-PCR) to confirm or rule out malaria infections and to identify Plasmodium species responsible for the infections. mRDTs detected Plasmodium infections in 50.3% of children and 17.1% of adults participating in the study, whereas RT-PCR assays yielded positive results for 59.5% children and 28.6% adults. Molecular tests detected multiple Plasmodium falciparum infections but also three infections with P. malariae, three with P. ovale and one with P. vivax. The obtained results have confirmed numerous asymptomatic Plasmodium infections among the BaAka Pygmies. The rates of asymptomatic malaria cases in adults were twice as high as those in children, which may be indicative of the gradual acquisition of protective immunity with age. The study findings have also demonstrated that although most cases of malaria in Africa are caused by P. falciparum, three other species are also present in the region.