Plasmodium falciparummsp2Genotypes and Multiplicity of Infections among Children under Five Years with Uncomplicated Malaria in Kibaha, Tanzania

Abstract

Genetic diversity of Plasmodium falciparum may pose challenges in malaria treatment and prevention through chemotherapy and vaccination. We assessed Plasmodium falciparum genetic diversity and multiplicity of infection (MOI) of P. falciparum infections and sort relationship of parasitaemia with P. falciparum msp2 genotypes as well as with the number of infecting clones. The study was carried out in Kibaha, Tanzania. Ninety-nine children under five years with uncomplicated malaria were recruited. Genetic diversity was analyzed by genotyping the msp2 gene using PCR-Restriction Fragment Length Polymorphism. Thirty-two different msp2 alleles were obtained. The msp2 3D7 allelic frequency was higher (48.1%) and more prevalent than FC27 (27.3%) (p < 0.05). Twenty-four percent of the infections were mixed alleles. The individuals with FC27 had high parasitemia compared to those with 3D7 alleles (p = 0.038). The mean MOI was low (1.4 clones, 95% CI 1.2–1.5). The P. falciparum population among children at Kibaha is composed of distinct P. falciparum clones, and parasites having 3D7 are more frequent than those with FC27 alleles. Individuals with parasite having FC27 alleles have high parasite densities suggesting that parasites with FC27 alleles may associate with severity of disease in Kibaha. Low MOI at Kibaha suggests low malaria transmission rate.

Variations in the quality of malaria-specific antibodies with transmission intensity in a seasonal malaria transmission area of Northern Ghana

“…This would have provided direct evidence of the association between MOI and the quality of antibody responses. This notwithstanding, the emerging pattern of association between MOI, albeit based on mostly MSP2 allele families, and transmission intensity in malaria endemic areas [ 38 – 40 , 56 – 58 ] provides the necessary basis for making the inferences drawn in this study.…”

“…Taken together, it can be hypothesized that individuals who experience simultaneous infection with multiple parasite variants will develop a more cross-reactive antibody profile compared to those who mostly experience clonal infections. A number of studies have demonstrated a greater average number of parasite variants per infected person, expressed as the multiplicity of infection (MOI), under high malaria transmission settings compared to corresponding findings in areas of low transmission [ 38 – 40 ]. The current study therefore assessed the functional quality of antibody responses in symptomatic and asymptomatic children between the ages of one and five years from an area in the Upper-East Region of Ghana with clearly marked seasonal malaria transmission.…”

“…For assessment of the relative proportions of strain-specific and cross reactive antibodies, Bland-Altman plots revealed a relatively higher preponderance of cross-reactive antibodies from September 2004 to January 2005, which cover the peak rainfall season and into the early part of the dry season, while relatively higher levels of strain-specific antibodies were elicited during the low transmission season and into the early part of the rainy season ( Fig 3 ). This observation may be closely linked with the diversity of infecting parasite strains over the transmission period; high transmission periods have been associated with multiple parasite strain infections, reflected by high MOIs in infected individuals while low transmission periods are predominantly associated with a greater proportion of clonal parasite infections [ 38 – 40 , 56 – 58 ]. These patterns are most likely a direct result of an upsurge in transmission vector population during the rainy periods and a decline during the dry periods [ 31 , 47 ].…”

The prevalence of submicroscopic Plasmodium falciparum gametocyte carriage and multiplicity of infection in children, pregnant women and adults in a low malaria transmission area in Southern Ghana

“…The 3D7 allelic types predominated in all the three study groups as compared to the FC27 allelic types, indicating its dominance in this geographical area. A number of studies conducted in Ghana and Tanzania have identified the 3D7 allelic parasite type to be dominant among the parasite populations [ 18 , 40 , 45 , 46 ]. Different P. falciparum parasite variants may influence gametocyte carriage differently, as was observed in this study where individuals carrying both 3D7 and FC27 allelic types of parasite had a higher risk of harbouring gametocytes compared to single 3D7 or FC27 allelic types.…”

“…This findings may suggest the possibility of limited immune responses against these parasite variants due to antigen-specific immunosuppression or immune tolerance, hence their ability to persist for longer periods and commit to gametocyte formation [ 47 ]. However, in other studies, the family-specific FC27 allelic type parasites have been shown to be associated with high parasite densities as well as involved in disease severity, suggesting they may be more pathogenic [ 46 , 48 ]. This underscores the need to investigate the potential role other family allelic type of parasites may play in gametocyte carriage in different study populations and transmission areas, since its effect may impact on transmission.…”