Reduction of multiplicity of infections but no change in msp2 genetic diversity in Plasmodium falciparum isolates from Congolese children after introduction of artemisinin-combination therapy

Abstract

BackgroundIn this first study conducted after the introduction of artemisinin-combination therapy (ACT), the major objective was to evaluate Plasmodium falciparum genetic diversity and multiplicity of infection in isolates from Congolese children between one and nine years of age enrolled and followed up for one year. The secondary objective was to characterize the msp2 profiles of P. falciparum isolates collected from successive malaria episodes in ten children who had four or more clinical episodes during the follow up.MethodsThree-hundred and thirteen children residing in southern part of Brazzaville participated in this study. Blood samples were obtained from all children at enrollment and checked for P. falciparum infection. Based on the one year follow-up data, two clinical groups were considered according to the number of malaria episodes presented over the follow up period: “protected”(children who did not experience any episode) and “unprotected” (those who experienced more that two episodes). Therefore, the msp2 genetic diversity of P. falciparum isolates collected at enrollment in the two groups was characterized by allele-specific nested PCR and compared. The msp2 profiles of P. falciparum isolates collected from successive malaria episodes was also characterized by allele-specific nested PCR.ResultsForty-three percent of FC27 and fifty-seven percent of 3D7 in protected vs fifty-six percent of FC27 and forty-four percent of 3D7 in isolates from unprotected children were detected. Seven and two alleles belonging to the FC27, and six and three alleles belonging to 3D7 families were distinguished in isolates from protected and unprotected children respectively. The mean multiplicity of infection (MOI) values at inclusion for the msp2 locus was 1.29 and 1.43 for protected and unprotected children respectively. 43 isolates were obtained from the ten children who had four or more clinical episodes during the follow up. A total of 63 alleles or fragments corresponding to 57% (36/63) FC27 and 43% (27/63) 3D7 were detected. The variant 400bp of FC27 was the most prevalent. 46% (20/43), 42% (18/43), 2% (1/43) and 2% (1/43) of isolates were found to have 1, 2, 3 and 4 parasite genotypes respectively and the mean MOI was 1.78.ConclusionThis study shows that the introduction of ACT in the Republic of Congo has reduced the MOI but not the genetic diversity of P. falciparum isolates from children living in Southern districts of Brazzaville.

Malaria epidemiological research in the Republic of Congo

“…A total of 8 published articles have been found, for which, different molecular markers have been used. The genes for the merozoite surface protein 1 and 2 have been used, msp2 alone has been used in four investigations [9, 15, 16, 34], msp1 and msp2 in one study [27], and microsatellites in two studies with one utilizing msp1 in addition to the microsatellite markers [11, 21]. …”

“…However, the MOI and the rate of isolates with multiple genotypes were found to be low, 1.3 and 28%, respectively [15]. The cohort of children enrolled in this study was followed up for a year to monitor uncomplicated falciparum malaria episodes and isolates collected from some of the children who experienced uncomplicated malaria were later on analysed by Ibara-Okabando et al [34] with regard to parasite diversity using msp2 as molecular marker. A high genetic diversity of parasite population was observed with 21 different alleles detected (11 for 3D7 family and 10 for the FC27).…”

“…A high genetic diversity of parasite population was observed with 21 different alleles detected (11 for 3D7 family and 10 for the FC27). Here, the MOI of 1.7 was determined and 54% the isolates harboured more than one msp2 genotype [34]. …”

Plasmodium falciparum infection in febrile Congolese children: prevalence of clinical malaria 10 years after introduction of artemisinin‐combination therapies

“…Since the introduction of ACTs in Republic of Congo (RoC) in 2006, a reduction of malaria clinical cases from 45% to 16% was observed . The prevalence of clinical malaria in children varies between 8% and 29% in Brazzaville and Pointe‐Noire, the two main cities in RoC .…”

Role of genetic factors and ethnicity on the multiplicity of Plasmodium falciparum infection in children with asymptomatic malaria in Yaoundé, Cameroon

“…Mean multiplicity of infection (MOI) was estimated by dividing the total number of distinct msp-2 genotypes detected by the number of positive samples [40].…”