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Genetic diversity of Plasmodium falciparum among school-aged children from the Man region, western Côte d'Ivoire.

Mara SE, Silué KD, Raso G, N'guetta SP, N'goran EK, Tanner M, Utzinger J, Ding XC - Malar. J. (2013)

Bottom Line: Plasmodium falciparum prevalence and parasitaemia were both found to be significantly lower in the highest altitude village.MOI varied significantly across villages but did not correlate with altitude nor children's age, and only to a limited extent with parasitaemia.Higher altitude was associated with lower prevalence of P. falciparum but not with reduced MOI, suggesting that, in this setting, MOI is not a good proxy for transmission.

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Affiliation: Département Environnement et Santé, Centre Suisse de Recherches Scientifiques en Côte d'Ivoire, 01 BP 1303 Abidjan 01, Côte d'Ivoire. xavier.ding@gmail.com.

ABSTRACT

Background: The genetic diversity of Plasmodium falciparum allows the molecular discrimination of otherwise microscopically identical parasites and the identification of individual clones in multiple infections. The study reported here investigated the P. falciparum multiplicity of infection (MOI) and genetic diversity among school-aged children in the Man region, western Côte d'Ivoire.

Methods: Blood samples from 292 children aged seven to 15 years were collected in four nearby villages located at altitudes ranging from 340 to 883 m above sea level. Giemsa-stained thick and thin blood films were prepared and examined under a microscope for P. falciparum prevalence and parasitaemia. MOI and genetic diversity of the parasite populations were investigated using msp2 typing by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).

Results: Plasmodium falciparum prevalence and parasitaemia were both found to be significantly lower in the highest altitude village. Genotyping of the isolates revealed 25 potentially new msp2 alleles. MOI varied significantly across villages but did not correlate with altitude nor children's age, and only to a limited extent with parasitaemia. An analysis of molecular variance (AMOVA) indicated that a small, but close to statistical significance (p = 0.07), fraction of variance occurs specifically between villages of low and high altitudes.

Conclusions: Higher altitude was associated with lower prevalence of P. falciparum but not with reduced MOI, suggesting that, in this setting, MOI is not a good proxy for transmission. The evidence for partially parted parasite populations suggests the existence of local geographical barriers that should be taken into account when deploying anti-malarial interventions.

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msp2 allele frequencies across study sites. The overall (“Total”) and village-specific frequencies of each allele identified are indicated. Alleles in bold face are FC27-type and alleles in lightface are 3D7-type, * indicates private alleles.
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Figure 3: msp2 allele frequencies across study sites. The overall (“Total”) and village-specific frequencies of each allele identified are indicated. Alleles in bold face are FC27-type and alleles in lightface are 3D7-type, * indicates private alleles.

Mentions: Figure 3 displays the allelic frequencies observed at the respective study sites as well as when pooling all samples. The most prevalent allele in each village is the FC27-type allele WOS3, with a maximum local frequency of 11.1%. The second most prevalent allele in the two highest villages, Sandougou-soba and Mélapleu, is WOS10 (6.9% and 7.2%, respectively), while it is 3D7 (400) in Bogouiné II and the newly reported FC27-type allele Cot11 in Bloleu. These two alleles rank amongst the 18th and 9th most prevalent in the other locations, respectively. Between one and nine private alleles were identified in each village, but their local frequency did not exceed 1.4% (Figure 3). The lowest number of distinct msp2 alleles (39) was observed in Sandougou-soba, which is likely due to the lower number of individual infections sampled in this village as compared to the others (72 versus 186 to 235) [33] (Table 5). Nevertheless, 60 different alleles were identified out of 186 clonal infections in the low altitude village Bogouiné II, while only 58 alleles were observed from 235 infections in the high altitude village Mélapleu. This suggests that high altitude villages might display a lower diversity than low altitude ones. This observation is further supported by the fact that the number of effective alleles, that is the theoretical number of equally frequent alleles needed to achieve a level of diversity equal to the one observed, is higher in Bogouiné II and Bloleu (low altitude) than in Sandougou-soba and Mélapleu (high altitude), despite the fact that the number of clonal infection sampled is lower in both of these villages as compared to Mélapleu (Table 5).


Genetic diversity of Plasmodium falciparum among school-aged children from the Man region, western Côte d'Ivoire.

Mara SE, Silué KD, Raso G, N'guetta SP, N'goran EK, Tanner M, Utzinger J, Ding XC - Malar. J. (2013)

msp2 allele frequencies across study sites. The overall (“Total”) and village-specific frequencies of each allele identified are indicated. Alleles in bold face are FC27-type and alleles in lightface are 3D7-type, * indicates private alleles.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3842749&req=5

Figure 3: msp2 allele frequencies across study sites. The overall (“Total”) and village-specific frequencies of each allele identified are indicated. Alleles in bold face are FC27-type and alleles in lightface are 3D7-type, * indicates private alleles.
Mentions: Figure 3 displays the allelic frequencies observed at the respective study sites as well as when pooling all samples. The most prevalent allele in each village is the FC27-type allele WOS3, with a maximum local frequency of 11.1%. The second most prevalent allele in the two highest villages, Sandougou-soba and Mélapleu, is WOS10 (6.9% and 7.2%, respectively), while it is 3D7 (400) in Bogouiné II and the newly reported FC27-type allele Cot11 in Bloleu. These two alleles rank amongst the 18th and 9th most prevalent in the other locations, respectively. Between one and nine private alleles were identified in each village, but their local frequency did not exceed 1.4% (Figure 3). The lowest number of distinct msp2 alleles (39) was observed in Sandougou-soba, which is likely due to the lower number of individual infections sampled in this village as compared to the others (72 versus 186 to 235) [33] (Table 5). Nevertheless, 60 different alleles were identified out of 186 clonal infections in the low altitude village Bogouiné II, while only 58 alleles were observed from 235 infections in the high altitude village Mélapleu. This suggests that high altitude villages might display a lower diversity than low altitude ones. This observation is further supported by the fact that the number of effective alleles, that is the theoretical number of equally frequent alleles needed to achieve a level of diversity equal to the one observed, is higher in Bogouiné II and Bloleu (low altitude) than in Sandougou-soba and Mélapleu (high altitude), despite the fact that the number of clonal infection sampled is lower in both of these villages as compared to Mélapleu (Table 5).

Bottom Line: Plasmodium falciparum prevalence and parasitaemia were both found to be significantly lower in the highest altitude village.MOI varied significantly across villages but did not correlate with altitude nor children's age, and only to a limited extent with parasitaemia.Higher altitude was associated with lower prevalence of P. falciparum but not with reduced MOI, suggesting that, in this setting, MOI is not a good proxy for transmission.

View Article: PubMed Central - HTML - PubMed

Affiliation: Département Environnement et Santé, Centre Suisse de Recherches Scientifiques en Côte d'Ivoire, 01 BP 1303 Abidjan 01, Côte d'Ivoire. xavier.ding@gmail.com.

ABSTRACT

Background: The genetic diversity of Plasmodium falciparum allows the molecular discrimination of otherwise microscopically identical parasites and the identification of individual clones in multiple infections. The study reported here investigated the P. falciparum multiplicity of infection (MOI) and genetic diversity among school-aged children in the Man region, western Côte d'Ivoire.

Methods: Blood samples from 292 children aged seven to 15 years were collected in four nearby villages located at altitudes ranging from 340 to 883 m above sea level. Giemsa-stained thick and thin blood films were prepared and examined under a microscope for P. falciparum prevalence and parasitaemia. MOI and genetic diversity of the parasite populations were investigated using msp2 typing by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).

Results: Plasmodium falciparum prevalence and parasitaemia were both found to be significantly lower in the highest altitude village. Genotyping of the isolates revealed 25 potentially new msp2 alleles. MOI varied significantly across villages but did not correlate with altitude nor children's age, and only to a limited extent with parasitaemia. An analysis of molecular variance (AMOVA) indicated that a small, but close to statistical significance (p = 0.07), fraction of variance occurs specifically between villages of low and high altitudes.

Conclusions: Higher altitude was associated with lower prevalence of P. falciparum but not with reduced MOI, suggesting that, in this setting, MOI is not a good proxy for transmission. The evidence for partially parted parasite populations suggests the existence of local geographical barriers that should be taken into account when deploying anti-malarial interventions.

Show MeSH
Related in: MedlinePlus