RESUMO
Background: The genetic variation of Plasmodium falciparum has been studied to assess local malaria transmission genetic profile using evidence-based intervention measures. However, there are no known previous reports of P. falciparum polymorphism in Badewacho and Boset districts, Southern Ethiopia. The purpose of this study was to determine the genetic diversity of the merozoite surface protein-1 and -2 (msp-1 and msp-2) allelic families in P. falciparum isolates from an asymptomatic populations. Methods: This study was conducted from finger-prick blood samples spotted on 3 mm Whatman filter paper collected during a community-based cross-sectional study. Nested polymerase chain reaction amplification was used to type the allelic variants of msp-1 and msp-2. Results: From 669 asymptomatic study participants, a total of 50 samples positive for P. falciparum were included for molecular analysis. Of 50 positive samples, 43 P. falciparum isolates were successfully amplified for the msp-1 and msp-2 allelic families. A total of twelve different allele sizes (75-250 bp) were identified within the three allelic families of msp-1, whereas ten different allele sizes (250-500 bp) were detected within the two allelic families of msp-2. MAD20 had a higher allelic proportion, 65% among allelic families of msp-1, whereas the 3D7 allelic family 90.7% was higher in msp-2. A slightly higher frequency of polyclonal infection 53.5% was found in msp-2 allelic family, whereas a low proportion polyclonal infection 46.5% was found in msp-1 allelic family. The overall mean multiplicity of infection (MOI) for msp-1 and msp-2 was identical (MOI = 1.56). Correspondingly, the expected heterozygosity (He) value for msp-1 (He = 0.23) and msp-2 (He = 0.22) was almost similar. Conclusions: The findings of this study revealed low genetic diversity of the msp-1 and msp-2 allelic families in P. falciparum isolates. However, continued monitoring status of the local genetic diversity profile in the P. falciparum population is required to support current malaria control and elimination strategies.
RESUMO
BACKGROUND: One of the major challenges in developing an effective vaccine against asexual stages of Plasmodium falciparum is genetic polymorphism within parasite population. Understanding the genetic polymorphism like block 2 region of merozoite surface protein-1 (msp-1) gene of P. falciparum enlighten mechanisms underlining disease pathology, identification of the parasite clone profile from the isolates, transmission intensity and potential deficiencies of the ongoing malaria control and elimination efforts in the locality. Detailed understanding of local genetic polymorphism is an input to pave the way for better management, control and elimination of malaria. The aim of this study was to detect the most frequent allelic variant of the msp-1 gene of P. falciparum clinical isolates from selected health facilities in Adama town and its surroundings, Oromia, Ethiopia. METHODS: One hundred thirty-nine clinical isolates were successfully amplified for msp-1 gene using specific primers. Nested PCR amplification was conducted targeting K1, MAD20, and R033 alleles followed by gel electrophoresis for fragment analysis. Based on the detection of a PCR fragment, infections were classified as monoclonal or multiple infections. RESULTS: 19 different size polymorphism of msp-1 gene were identified in the study, with 67(48%) MAD20, 18 (13%) K-1 and 18 (13%) RO33 allelic family. Whereas, the multiple infections were 21(15%), 8 (5.8%), 4(2.9%), 3(2.2%) for MAD20 + K-1, MAD20 + RO33, K-1 + RO33, and MAD20 + K-1, RO33, respectively. The overall Multiplicity of infection (MOI) was 1.3 and the expected heterozygosity (He) was 0.39 indicating slightly low falciparum malaria transmission. CONCLUSION: The status of msp-1 allele size polymorphism, MOI and He observed in the study revealed the presence of slightly low genetic diversity of P. falciparum clinical isolates. However, highly frequent MAD20 allelic variant was detected from clinical isolates in the study area. Moreover, the driving force that led to high predominance of MAD20 allelic variant revealed in such malaria declining region demands further research.