BACKGROUND: The genetic diversity of Plasmodium falciparum provides the parasite with many effective immune evasion and drug resistance mechanisms. This phenomenon is a major problem in eradicating malaria globally. This study aimed to assess merozoite surface protein 2 polymorphisms in P. falciparum isolates from Northwest Ethiopia. METHOD: A cross-sectional study was conducted to assess merozoite surface protein 2 polymorphisms in P. falciparum isolates from selected malarious areas in Northwest Ethiopia from April to June 2021. A convenience sampling technique was used to select 150 study participants. A finger prick blood sample was collected to prepare blood films and dried blood spots for molecular genotyping. The merozoite surface protein 2 allele frequency and multiplicity of infection were computed. Linear regression was employed to evaluate the associations between the multiplicity of infection, parasite density, and age by calculating Spearman's rank correlation coefficients. A P value <
0.05 was considered to indicate statistical significance. RESULT: Polymorphism analysis was performed on 126 P. falciparum isolates. There were 38 different merozoite surface protein 2 alleles, 20 of which corresponded to the IC/3D7 allelic family and 18 to the FC27 allelic family. Most patients contained multiple infections, and the mean multiplicity of infection was 3.46. There was no statistically significant difference in the multiplicity of infection in relation to the age of patients (P = 0.646). However, a statistically significant correlation was found between parasite density and the multiplicity of infection (P = 0.046). The heterozygosity index for merozoite surface protein 2 was 0.948. CONCLUSION: This study showed that P. falciparum isolates contain multiple genotypes with a high multiplicity of infections and mixed strain infection, suggesting extensive genetic diversity and a high level of malaria transmission. This genetic variability could complicate malaria treatment and control efforts, as it can facilitate the emergence and spread of drug-resistant strains. Consequently, the findings highlight the complex malaria epidemiology in the region and emphasize the need for intensified efforts to control malaria transmission and prevent the probable emergence of drug resistance alleles in the study area.