Low genetic diversity of Plasmodium falciparum merozoite surface protein 1 and 2 and multiplicity of infections in western Ethiopia following effective malaria interventions

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Abstract Background: Genetic diversity of malaria parasites can inform the intensity of transmission and poses a major threat to malaria control and elimination interventions. Characterization of the genetic diversity would provide essential information about the ongoing control efforts. This study aimed to explore allelic polymorphism of merozoite surface protein 1 (msp1) and merozoite surface protein 2 (msp2) to determine the genetic diversity and multiplicity of P. falciparum infections circulating in high and low transmission sites in western Ethiopia. Method: Parasite genomic DNA was extracted from a total of 225 dried blood spot collected from confirmed uncomplicated P. falciparum malaria infected patients in western Ethiopia. Of these, (163) 72.4% and (62) 27.6 % of the samples were collected in high and low transmission areas, respectively. Polymorphic msp1 and msp2 genes were used to explore the genetic diversity and multiplicity of falciparum malaria infections. Msp1 genotyping was successful in 141/163 and 55/62 samples collected from high and low transmission areas, respectively. On the other hand, genotyping of msp2 was carried out among 85.3 % and 96.8 % of the samples collected in high and low transmission sites, respectively. P. falciparum msp1 and msp2 genes were amplified by nested PCR and the PCR products were analyzed by Qiaxcel software. A p-value of less or equal to 0.05 was considered significant.Result: High prevalence of falciparum malaria was identified in children less than 15 years as compared with those ≥ 15 years old (AOR= 2.438, P=0.005). The three allelic families of msp1 (K1, MAD20, and RO33) and the two allelic families of msp2 (FC27 and 3D7), were observed in samples collected in high and low transmission areas. However, MAD 20 and FC 27 alleles were the predominant allelic families in both settings. P. falciparum isolates circulating in western Ethiopia had low genetic diversity and mean MOI. No difference in mean MOI between high transmission site (mean MOI 1.104) compared with low transmission area (mean MOI 1.08) (p> 0.05). Expected Heterozygosity of msp1 gene was slightly higher in isolates collected from high transmission site (He= 0.17) than those isolates from low transmission (He= 0.12). However, the heterozygosity of msp2 gene was not different in both settings (Pfmsp2: 0.04 in high transmission; pfmsp2: 0.03 in low transmission).Conclusion: P. falciparum from clinical malaria cases in western Ethiopia have low genetic diversity and multiplicity of infection irrespective of the intensity of transmission at the site of sampling. These may be signalling the effectiveness of malaria control strategies in Ethiopia; although further studies are required to determine how specific intervention strategies and other parameters that drive the pattern.

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