High Burden of Febrile Sub-microscopic Plasmodium Mixed Infections in Central India: A Cross-Sectional Study

Malaria continues as a public health threat through symptomatic/febrile cases, asymptomatic and low-density infections of Plasmodium falciparum, P. vivax, and their mixed infections. Mixed infections have not been studied much regarding their burden, clinical manifestations, and implications, and therefore, this study was conducted.

Febrile patients were recruited from four patient-care settings from June to November 2020 through the collection of dried blood spots (DBS) and their paired microscopy and/or rapid diagnostic test (RDT) data. Polymerase chain reaction (PCR)-based molecular diagnosis of both parasite species was performed from genomic DNA isolated from the DBS. Clinico-demographic details were recorded from patients from one of the sites, wherein patients with mixed infections were telephonically followed for subsequent clinical development.

Out of the 1030 samples collected and analyzed, 27% (280) were infected with P. falciparum and/or P. vivax: 188 (18%) mono-P. falciparum, 6 (0.5%) mono-P. vivax and 86 (8%) mixed. None of the infections were detected by microscopy and/or RDT, meaning that all 27% were febrile sub-microscopic infections with 8% burden of mixed infections. The quality of microscopic slides was found to be unsatisfactory when a sub-sample of slides was cross-examined by level 1-competent microscopists. None of the nine mixed-infection patients from Gandhi Medical College and Hospital (GMCH) reported recurrences or any clinical development during the 12-month follow-up. No clinically/statistically significant difference was observed between mono- and mixed infections.

A high 27% febrile sub-microscopic Plasmodium infections with 8% mixed infections represent a significant challenge for malaria elimination, considering the quality of microscopy and the fact that Madhya Pradesh is classified under category 1 in the National Strategic Plan for malaria elimination 2023-2027.