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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

Spatial distributions of Plasmodium falciparum (A) and Plasmodium vivax (B) haplotypes in Temotu Province. A map of the Temotu Province is shown in the upper left panel while enlarged maps of particular islands are shown in the right and lower panel. Villages where parasites were genotyped are marked on the map. The type and frequency of haplotypes at each village are represented by a pie chart. The size of the pie chart is proportional to the number of parasites typed. White portions within pies indicate unique haplotypes observed once, while coloured portions indicate haplotypes observed more than once. Identical haplotypes are represented by the same colour. In Figure 4A, dominant P. falciparum haplotypes PfH3, PfH4, PfH6 and PfH11 are represented by blue, red, green and purple, respectively.
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Figure 4: Spatial distributions of Plasmodium falciparum (A) and Plasmodium vivax (B) haplotypes in Temotu Province. A map of the Temotu Province is shown in the upper left panel while enlarged maps of particular islands are shown in the right and lower panel. Villages where parasites were genotyped are marked on the map. The type and frequency of haplotypes at each village are represented by a pie chart. The size of the pie chart is proportional to the number of parasites typed. White portions within pies indicate unique haplotypes observed once, while coloured portions indicate haplotypes observed more than once. Identical haplotypes are represented by the same colour. In Figure 4A, dominant P. falciparum haplotypes PfH3, PfH4, PfH6 and PfH11 are represented by blue, red, green and purple, respectively.

Mentions: Two of the 19 P. falciparum haplotypes were observed on more than one island groups: PfH3, the most frequent haplotype, occurred on Santa Cruz (n = 15) and Utupua/Vanikoro (n = 2); PfH4 occurred on Santa Cruz (n = 6) and Duff /Reef Islands (n = 2) (Figure 4A). In contrast, only two of the 58 P. vivax haplotypes were shared between islands at the time of survey: PvH27 was observed once on Santa Cruz and twice on outer islands while PvH11 was observed once on Reef/Duff Islands and twice on Santa Cruz (Figure 4B).


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)

Spatial distributions of Plasmodium falciparum (A) and Plasmodium vivax (B) haplotypes in Temotu Province. A map of the Temotu Province is shown in the upper left panel while enlarged maps of particular islands are shown in the right and lower panel. Villages where parasites were genotyped are marked on the map. The type and frequency of haplotypes at each village are represented by a pie chart. The size of the pie chart is proportional to the number of parasites typed. White portions within pies indicate unique haplotypes observed once, while coloured portions indicate haplotypes observed more than once. Identical haplotypes are represented by the same colour. In Figure 4A, dominant P. falciparum haplotypes PfH3, PfH4, PfH6 and PfH11 are represented by blue, red, green and purple, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 4: Spatial distributions of Plasmodium falciparum (A) and Plasmodium vivax (B) haplotypes in Temotu Province. A map of the Temotu Province is shown in the upper left panel while enlarged maps of particular islands are shown in the right and lower panel. Villages where parasites were genotyped are marked on the map. The type and frequency of haplotypes at each village are represented by a pie chart. The size of the pie chart is proportional to the number of parasites typed. White portions within pies indicate unique haplotypes observed once, while coloured portions indicate haplotypes observed more than once. Identical haplotypes are represented by the same colour. In Figure 4A, dominant P. falciparum haplotypes PfH3, PfH4, PfH6 and PfH11 are represented by blue, red, green and purple, respectively.
Mentions: Two of the 19 P. falciparum haplotypes were observed on more than one island groups: PfH3, the most frequent haplotype, occurred on Santa Cruz (n = 15) and Utupua/Vanikoro (n = 2); PfH4 occurred on Santa Cruz (n = 6) and Duff /Reef Islands (n = 2) (Figure 4A). In contrast, only two of the 58 P. vivax haplotypes were shared between islands at the time of survey: PvH27 was observed once on Santa Cruz and twice on outer islands while PvH11 was observed once on Reef/Duff Islands and twice on Santa Cruz (Figure 4B).

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