Genetic polymorphism of Plasmodium falciparum MSP-2 (3D7/IC) and multiplicity of infection in N’Djamena, Chad

Malaria remains one of the most widespread endemic diseases in Africa. Molecular epidemiological studies of Plasmodium falciparum genetic diversity are essential for understanding transmission dynamics and informing effective control strategies. This study aimed to assess the genetic polymorphism of the merozoite surface protein 2 (msp2) 3D7/IC allelic family and multiplicity of infection in malaria patients. A cross-sectional analytical study was conducted from July to September 2024. Blood samples were collected from 217 participants attending Our Lady of the Apostles Hospital in N'Djamena, Chad. Malaria infection and parasite density were determined using immunochromatographic tests and thick blood smears. Parasite DNA was extracted using the Chelex-100 method, and the msp2 3D7/IC allelic family was amplified by nested PCR. Phylogenetic analysis was performed using the Lower Left matrix with R software, and statistical analyses were conducted using Excel 2016 and SPSS version 23. The prevalence of Plasmodium falciparum infection was 23.5%, while the molecular frequency of the msp2 3D7/IC allelic family was 94.11%. Genetic polymorphism within this allelic family was observed, with a predominance of one genotype (18.46%) and low-frequency alleles ranging between 560 and 570 base pairs (3.07% and 1.53%, respectively). Single-clone infections were most frequent (64.65%), followed by double (33.33%) and triple infections (2.08%), with no quadruple infections detected. Phylogenetic analysis revealed eight clades, with clades 1, 4, and 7 showing a higher concentration of genetically related isolates. This study demonstrates substantial genetic diversity and multiplicity offalciparum infections within the msp-2 3D7/IC allelic family, reflecting ongoing malaria transmission in the study area. The findings underscore the importance of expanding molecular surveillance to include additional allelic families and multiple sites to generate more comprehensive data for national malaria control strategies.