Genetic Diversity and Complexity of Plasmodium Falciparum Infections in the Microenvironment Among Siblings of the Same Household in North-central Nigeria

Abstract

Background: Plasmodium falciparum parasites are known to exhibit extensive genetic diversity in areas of high transmission intensity and infected individuals in such communities often harbour several complex mixture of parasite clones with different genetic characteristics. However, in the microenvironment, the extent of genetic diversity of the P. falciparum parasites remain largely unknown. In this study therefore, we investigated the complexity of P. falciparum infections in households, among symptomatic siblings living under the same roof in North-central Nigeria.Methods: Children were enrolled into the study if they were at least two from a household and presented with symptoms of uncomplicated malaria. Clinical malaria was confirmed by light microscopy of Giemsa stained thick and thin blood films. Genomic DNA was isolated from blood spots on filter paper. Molecular characterization of P. falciparum isolates was done by allele-specific nested PCR of the highly polymorphic merozoite surface protein-2 (MSP-2) gene.Results: 93 children from 43 households were enrolled into this study. A total of 26 different MSP-2 alleles were identified from 215 fragments (range: 180-480bp). Majority of the isolates [65.6% (n=61)] were polyclonal infections consisting of 2-6 clones and were significantly more common with the FC27 allelic family (p = 0.036). The multiplicity of infection (MOI) per household ranged from 1.0 to 4.5 while the overall MOI in the study population was 2.31. The pattern of distribution of MSP-2 allele types among the households fell into two categories: households where both MSP-2 allele types (FC27 and 3D7) were present; and households where only one MSP-2 allele type (FC27 or 3D7) was present. Majority of the households [88.4% (n=38)], had both MSP-2 allele types but they were disproportionately distributed among the children while in a few households [11.6% (n=5)], all the children were infected with only one type of MSP-2 allele.Conclusion: Our findings showed that P. falciparum isolates exhibit remarkable degree of genetic diversity in the microenvironment and are composed mainly of multiclonal infections, which is an indication of a high ongoing parasite transmission. This suggests that the microenvironment is an important area of focus for malaria control interventions and for evaluating intervention programmes.

Dinucleotide (AC)n Repeat Polymorphism (rs36213840) in the Promoter Region of IL18R1 Gene and Genetic Susceptibility to Severe Malaria

“…This study was conducted in Lafia, a city located about 190km away from Abuja, the capital of Nigeria. Lafia is situated within the middle belt region in north-central Nigeria and lies within Nigeria's Guinea savannah ecological zone as previously described [28] and malaria transmission is known to be stable and intense in the region [29].…”

“…Blood films were examined for malaria parasites under high-power oil immersion objectives at 1000× magnification. Parasitaemia was quantified relative to approximately 250 white blood cells (WBC) on thick films and estimated as parasites per microlitre (µl) assuming a mean WBC of 8,000 per µl of blood as described previously [28]. Blood smears were labelled negative if no parasites were seen after examination of 200 oil immersion fields.…”