Abstract
BackgroundMalaria remains a major global health burden despite the intensification of control efforts, due partly to the lack of an effective vaccine. Information on genetic diversity in natural parasite populations constitutes a major impediment to vaccine development efforts and is limited in some endemic settings. The present study characterized diversity by investigating msp1 block 2 polymorphisms and the relationship between the allele families with ethnodemographic indices and clinical phenotype.MethodIndividuals with asymptomatic parasitaemia (AP) or uncomplicated malaria (UM) were enrolled from rural, semi-rural and semi-urban localities at varying altitudes along the slope of mount Cameroon. P. falciparum malaria parasitaemic blood screened by light microscopy was depleted of leucocytes using CF11 cellulose columns and the parasite DNA genotyped by nested PCR.ResultsLength polymorphism was assessed in 151 field isolates revealing 64 (5) and 274 (22) distinct recombinant and major msp1 allelic fragments (genotypes) respectively. All family specific allelic types (K1, MAD20 and RO33) as well as MR were observed in the different locations, with K1 being most abundant. Eighty seven (60 %) of individuals harbored more than one parasite clone, with a significant proportion (p = 0.009) in rural compared to other settings. AP individuals had higher (p = 0.007) K1 allele frequencies but lower (p = 0.003) mean multiplicity of genotypes per infection (2.00 ± 0.98 vs. 2.56 ± 1.17) compared to UM patients.ConclusionsThese results indicate enormous diversity of P. falciparum in the area and suggests that allele specificity and complexity may be relevant for the progression to symptomatic disease.
Highlights
Malaria remains a major global health burden despite the intensification of control efforts, due partly to the lack of an effective vaccine
asymptomatic parasitaemia (AP) individuals had higher (p = 0.007) K1 allele frequencies but lower (p = 0.003) mean multiplicity of genotypes per infection (2.00 ± 0.98 vs. 2.56 ± 1.17) compared to uncomplicated malaria (UM) patients. These results indicate enormous diversity of P. falciparum in the area and suggests that allele specificity and complexity may be relevant for the progression to symptomatic disease
This may be due to the concomitant infection with different parasite genotypes, bearing numerous allelic forms of asexual blood-stage P. falciparum antigens, over successive infections and within a given infection that delay the acquisition of immunity [8]
Summary
Malaria remains a major global health burden despite the intensification of control efforts, due partly to the lack of an effective vaccine. Malaria remains a major global human health-threatening disease, resulting in approximately 207 million clinical cases and 627,000 deaths each year, mainly in sub-Saharan Africa [1]. Individuals born in malariaholoendemic areas suffer repeated malaria attacks in infancy and it takes 3 to 5 years to develop immunity that confers protection against parasitemia and illness. This may be due to the concomitant infection with different parasite genotypes, bearing numerous allelic forms of asexual blood-stage P. falciparum antigens, over successive infections and within a given infection that delay the acquisition of immunity [8]. The extent of multiple-genotype infections sheds light on malaria transmission, parasite diversity, and the development of immunity
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