Resumo

MUNZHEDZI, M et al. Prevalence of Plasmodium species in asymptomatic individuals in North-Eastern South Africa: 2018 - 2019. SAMJ, S. Afr. med. j. [online]. 2025, vol.115, n.8, pp.36-44. ISSN 2078-5135.  https://doi.org/10.7196/SAMJ.2025.v115i7.2273.

BACKGROUND. Asymptomatic Plasmodium infections in endemic areas pose a challenge to malaria prevention and control strategies. The Ha-Lambani area in Vhembe district, Limpopo Province, South Africa, experiences periodic malaria outbreaks, possibly influenced by asymptomatic Plasmodium infections. In addition, the identification and monitoring of the Plasmodium falciparum Kelch 13 (Pfk13) gene associated with artemisinin resistance are crucial for understanding the emergence and spread of drug-resistant malaria in endemic areas. OBJECTIVE. To determine the prevalence of asymptomatic Plasmodium infection and Pfk13 gene polymorphisms in the Ha-Lambani area in the absence of a malaria outbreak. METHODS. Finger-prick dried blood spots from 985 asymptomatic individuals were collected from November 2018 to May 2019. A P. falciparum-specific rapid diagnostic test (RDT) was used to test for Plasmodium infection. High-resolution melt (HRM) analysis was used to test for P. falciparum, P. ovale, P. vivax and P. malariae. The prevalence of Plasmodium infection was determined by the proportion of positive cases detected by at least one of the tests. The Pfk13 gene was amplified from P. falciparum-positive samples, sequenced by Sanger and Illumina next-generation sequencing (NGS) and analysed for genetic diversity and resistance mutations to artemisinin. RESULTS. A prevalence of 7.1% (70/985; 95% confidence interval (CI): 0.054 - 0.087) of Plasmodium infection was observed. The dominant species was P. ovale (57.14%; n=40), followed by P. falciparum (37.1%; n=26), P. malariae (1.43%) and P. vivax (1.43%). Mixed infections were P. falciparum/P. ovale (2.9%). Plasmodium infections differed significantly by village (p<0.01). The Pfk13 gene was amplified from 5/30 (95% CI: 0.03 - 0.29). Analysis of NGS reads revealed 57 single nucleotide polymorphisms (SNPs) across the Pfk13 gene (>20% minority level). Up to 70.1% (39/57; 95% CI: 0.59 - 0.83) of the SNPs were non-synonymous and none was previously associated with artemisinin resistance. However, novel SNPs (H719Q, P701T, M472I, I526R and P443S) were detected in the propeller domain. CONCLUSION. A relatively high asymptomatic Plasmodium infection prevalence was observed in the study area, with P. ovale being the most prevalent species. Therefore, P. ovale infections may be missed with the Plasmodium RDT. R21 and RTS,S vaccines may not offer protection against P. ovale in the study area. Further research is needed to link asymptomatic infections in the study area and the periodic malaria outbreaks, and to determine the significance of the novel SNP in the Pfk13 gene.

Palavras-chave : asymptomatic Plasmodium infections; high-resolution melt analysis; Pfk13; NGS; malaria; Ha-Lambani; South Africa.

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