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Population genetics of Plasmodium falciparum and Plasmodium vivax and asymptomatic malaria in Temotu Province, Solomon Islands.

Gray KA, Dowd S, Bain L, Bobogare A, Wini L, Shanks GD, Cheng Q - Malar. J. (2013)

Bottom Line: Forty-five P. falciparum and 67 P. vivax samples collected in the 2008 baseline survey were successfully genotyped using eight P. falciparum and seven P. vivax microsatellite markers.Interestingly, a dominant haplotype was significantly associated with fever and high parasite density.The genetic diversity, population structure and distribution of strains indicate that transmission of P. falciparum was low, but that of P. vivax was still high in 2008.

View Article: PubMed Central - HTML - PubMed

Affiliation: Drug Resistance and Diagnostics, Australian Army Malaria Institute, Weary Dunlop Drive, Gallipoli Barracks, Enoggera, QLD, 4051, Australia. qin.cheng@defence.gov.au.

ABSTRACT

Background: Temotu Province, Solomon Islands is progressing toward malaria elimination. A baseline survey conducted in 2008 showed that most Plasmodium infections in the province were of low parasite density and asymptomatic infections. To better understand mechanisms underlying these malaria transmission characteristics genetic diversity and relationships among Plasmodium falciparum and Plasmodium vivax populations in the province were examined.

Methods: Forty-five P. falciparum and 67 P. vivax samples collected in the 2008 baseline survey were successfully genotyped using eight P. falciparum and seven P. vivax microsatellite markers. Genetic diversity, relationships and distribution of both P. falciparum and P. vivax populations were analysed.

Results: Plasmodium falciparum population exhibited low diversity with 19 haplotypes identified and had closely related clusters indicating clonal expansion. Interestingly, a dominant haplotype was significantly associated with fever and high parasite density. In contrast, the P. vivax population was highly diverse with 58 haplotypes identified that were not closely related. Parasite populations between different islands in the province showed low genetic differentiation.

Conclusion: The low diversity and clonal population of P. falciparum population may partially account for clinical immunity developed against illness. However, it is possible that importation of a new P. falciparum strain was the major cause of illness. High diversity in P. vivax population and low relatedness between strains suggested clinical immunity to P. vivax may be maintained by different mechanisms. The genetic diversity, population structure and distribution of strains indicate that transmission of P. falciparum was low, but that of P. vivax was still high in 2008. These data will be useful for assessing changes in malaria transmission resulting from interventions.

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Related in: MedlinePlus

The number of haplotypes and haplotype frequency for Plasmodium falciparum and Plasmodium vivax. Only haplotypes with frequencies greater than 0.03, i e, >3%, are indicated in the figure (haplotype; percentage).
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Figure 3: The number of haplotypes and haplotype frequency for Plasmodium falciparum and Plasmodium vivax. Only haplotypes with frequencies greater than 0.03, i e, >3%, are indicated in the figure (haplotype; percentage).

Mentions: Overall, 8-loci-combined haplotypes were determined for 45 of P. falciparum. The median age of these subjects was 6.5 years (range from 1 to 60) with a median parasite density of 480/μL (range from 0 to 94,000/μL). The number of alleles per locus ranged from three to seven with two markers (Polyα and PfPK2) having the highest number of alleles (Table 1). Allele frequencies for each locus are illustrated in Figure 2. Combination of allelic types at four loci (Polyα, PfPK2, TAA87 and TAA81) produced a total of 19 haplotypes (PfH1-PfH19) from 45 P. falciparum samples examined (Table 1 and Figure 3). The number of haplotypes did not increase when four additional markers were typed (Table 1). Two haplotypes (PfH3 and PfH4) consisted of 38 and 18% of the P. falciparum population while the remaining 17 haplotypes made up 2-7% each. The expected heterozygosity (HE) for each locus ranged from 0.27 to 0.71 for P. falciparum with a mean of 0.54 (± 0.05, Table 1). There was no significant difference in HE of P. falciparum between Santa Cruz and outer islands (Mann Whitney test, P = 0.55).


Population genetics of Plasmodium falciparum and Plasmodium vivax and asymptomatic malaria in Temotu Province, Solomon Islands.

Gray KA, Dowd S, Bain L, Bobogare A, Wini L, Shanks GD, Cheng Q - Malar. J. (2013)

The number of haplotypes and haplotype frequency for Plasmodium falciparum and Plasmodium vivax. Only haplotypes with frequencies greater than 0.03, i e, >3%, are indicated in the figure (haplotype; percentage).
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4222835&req=5

Figure 3: The number of haplotypes and haplotype frequency for Plasmodium falciparum and Plasmodium vivax. Only haplotypes with frequencies greater than 0.03, i e, >3%, are indicated in the figure (haplotype; percentage).
Mentions: Overall, 8-loci-combined haplotypes were determined for 45 of P. falciparum. The median age of these subjects was 6.5 years (range from 1 to 60) with a median parasite density of 480/μL (range from 0 to 94,000/μL). The number of alleles per locus ranged from three to seven with two markers (Polyα and PfPK2) having the highest number of alleles (Table 1). Allele frequencies for each locus are illustrated in Figure 2. Combination of allelic types at four loci (Polyα, PfPK2, TAA87 and TAA81) produced a total of 19 haplotypes (PfH1-PfH19) from 45 P. falciparum samples examined (Table 1 and Figure 3). The number of haplotypes did not increase when four additional markers were typed (Table 1). Two haplotypes (PfH3 and PfH4) consisted of 38 and 18% of the P. falciparum population while the remaining 17 haplotypes made up 2-7% each. The expected heterozygosity (HE) for each locus ranged from 0.27 to 0.71 for P. falciparum with a mean of 0.54 (± 0.05, Table 1). There was no significant difference in HE of P. falciparum between Santa Cruz and outer islands (Mann Whitney test, P = 0.55).

Bottom Line: Forty-five P. falciparum and 67 P. vivax samples collected in the 2008 baseline survey were successfully genotyped using eight P. falciparum and seven P. vivax microsatellite markers.Interestingly, a dominant haplotype was significantly associated with fever and high parasite density.The genetic diversity, population structure and distribution of strains indicate that transmission of P. falciparum was low, but that of P. vivax was still high in 2008.

View Article: PubMed Central - HTML - PubMed

Affiliation: Drug Resistance and Diagnostics, Australian Army Malaria Institute, Weary Dunlop Drive, Gallipoli Barracks, Enoggera, QLD, 4051, Australia. qin.cheng@defence.gov.au.

ABSTRACT

Background: Temotu Province, Solomon Islands is progressing toward malaria elimination. A baseline survey conducted in 2008 showed that most Plasmodium infections in the province were of low parasite density and asymptomatic infections. To better understand mechanisms underlying these malaria transmission characteristics genetic diversity and relationships among Plasmodium falciparum and Plasmodium vivax populations in the province were examined.

Methods: Forty-five P. falciparum and 67 P. vivax samples collected in the 2008 baseline survey were successfully genotyped using eight P. falciparum and seven P. vivax microsatellite markers. Genetic diversity, relationships and distribution of both P. falciparum and P. vivax populations were analysed.

Results: Plasmodium falciparum population exhibited low diversity with 19 haplotypes identified and had closely related clusters indicating clonal expansion. Interestingly, a dominant haplotype was significantly associated with fever and high parasite density. In contrast, the P. vivax population was highly diverse with 58 haplotypes identified that were not closely related. Parasite populations between different islands in the province showed low genetic differentiation.

Conclusion: The low diversity and clonal population of P. falciparum population may partially account for clinical immunity developed against illness. However, it is possible that importation of a new P. falciparum strain was the major cause of illness. High diversity in P. vivax population and low relatedness between strains suggested clinical immunity to P. vivax may be maintained by different mechanisms. The genetic diversity, population structure and distribution of strains indicate that transmission of P. falciparum was low, but that of P. vivax was still high in 2008. These data will be useful for assessing changes in malaria transmission resulting from interventions.

Show MeSH
Related in: MedlinePlus