Increasing trends of malaria in a border area of the Greater Mekong Subregion

Geng, Jiawei; Malla, Pallavi; Zhang, Jiaqi; Xu, Shiling; Li, Cuiying; Zhao, Yan; Wang, Qinghui; Kyaw, Myat Phone; Cao, Yaming; Yang, Zhaoqing

doi:10.1186/s12936-019-2924-6

Cited by 44 publications

(60 citation statements)

References 18 publications

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“…The CMB area has been traditionally malaria hyper-endemic with both P. falciparum and P. vivax transmission. Although recent malaria control efforts have sharply reduced the P. falciparum incidence [35], P. vivax incidence remained consistently high and even experienced outbreaks in recent years [9,36]. At the CMB, 50 samples were collected in 2004 to represent the parasite population prior to the implementation of malaria elimination measures, while 52 samples collected in 2016 represented the parasites after scalingup of malaria control.…”

Section: Study Sites and Plasmodium Vivax Clinical Samplesmentioning

confidence: 99%

“…The scale-up of malaria control efforts in countries of the GMS has led to substantial changes in malaria epidemiology with a noticeable rising proportion of vivax malaria [5,34]. In the China-Myanmar border (CMB) areas, P. vivax not only has become the predominant Plasmodium species in recent years [35], but also has caused several malaria outbreaks [9,36]. Even in the international border regions, malaria transmission is concentrated in separated hotspots, and among which gene flow is expected to be low [37].…”

Section: Introductionmentioning

confidence: 99%

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Dynamics of Plasmodium vivax populations in border areas of the Greater Mekong sub-region during malaria elimination

Zhao

et al. 2020

Malar J

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Background: Countries within the Greater Mekong Sub-region (GMS) of Southeast Asia have committed to eliminating malaria by 2030. Although the malaria situation has greatly improved, malaria transmission remains at international border regions. In some areas, Plasmodium vivax has become the predominant parasite. To gain a better understanding of transmission dynamics, knowledge on the changes of P. vivax populations after the scale-up of control interventions will guide more effective targeted control efforts. Methods:This study investigated genetic diversity and population structures in 206 P. vivax clinical samples collected at two time points in two international border areas: the China-Myanmar border (CMB) (n = 50 in 2004 and n = 52 in 2016) and Thailand-Myanmar border (TMB) (n = 50 in 2012 and n = 54 in 2015). Parasites were genotyped using 10 microsatellite markers.Results: Despite intensified control efforts, genetic diversity remained high (H E = 0.66-0.86) and was not significantly different among the four populations (P > 0.05). Specifically, H E slightly decreased from 0.76 in 2004 to 0.66 in 2016 at the CMB and increased from 0.80 in 2012 to 0.86 in 2015 at the TMB. The proportions of polyclonal infections varied significantly among the four populations (P < 0.05), and showed substantial decreases from 48.0% in 2004 to 23.7 at the CMB and from 40.0% in 2012 to 30.7% in 2015 at the TMB, with corresponding decreases in the multiplicity of infection. Consistent with the continuous decline of malaria incidence in the GMS over time, there were also increases in multilocus linkage disequilibrium, suggesting more fragmented and increasingly inbred parasite populations. There were considerable genetic differentiation and sub-division among the four tested populations. Temporal genetic differentiation was observed at each site (F ST = 0.081 at the CMB and F ST = 0.133 at the TMB). Various degrees of clustering were evident between the older parasite samples collected in 2004 at the CMB and the 2016 CMB and 2012 TMB populations, suggesting some of these parasites had shared ancestry. In contrast, the 2015 TMB population was genetically distinctive, which may reflect a process of population replacement. Whereas the effective population size © The Author(s) 2020. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article' s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article' (N e ) at the CMB showed a decrease from 4979 in 2004 to 3052 in 2016 with the infinite allele model, the N e at the TMB experienced an increase from 6289 to 10,259. Conclusions:With enhanced contr...

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Section: Study Sites and Plasmodium Vivax Clinical Samplesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Dynamics of Plasmodium vivax populations in border areas of the Greater Mekong sub-region during malaria elimination

Zhao

et al. 2020

Malar J

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Section: Study Sites and Plasmodium Vivax Clinical Samplesmentioning

confidence: 99%

Dynamics of Plasmodium vivax populations in border areas of the Greater Mekong Sub-region during malaria elimination

Li¹,

Yan

et al. 2020

Preprint

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Background Countries within the Greater Mekong Sub-region (GMS) of Southeast Asia have committed to eliminating malaria by 2030. Although the malaria situation has greatly improved, malaria transmission remains at international border regions. In some areas, Plasmodium vivax has become the predominant parasite. To gain a better understanding of transmission dynamics, knowledge on the changes of P. vivax populations after the scale-up of control interventions will guide more effective targeted control efforts. Methods This study investigated genetic diversity and population structures in 206 P. vivax clinical samples collected at two time points in two international border areas: the China-Myanmar border (CMB) (n=50 in 2004 and n=52 in 2016) and Thailand-Myanmar border (TMB) (n=50 in 2012 and n=54 in 2015). Parasites were genotyped using 10 microsatellite markers. Results Despite intensified control efforts, genetic diversity remained high ( H E = 0.66-0.86) and was not significantly different among the four populations ( P >0.05). Specifically, H E slightly decreased from 0.76 in 2004 to 0.66 in 2016 at the CMB and increased from 0.80 in 2012 to 0.86 in 2015 at the TMB. The proportions of polyclonal infections varied significantly among the four populations ( P < 0.05), and showed substantial decreases from 48.0% in 2004 to 23.7 at the CMB and from 40.0% in 2012 to 30.7% in 2015 at the TMB, with corresponding decreases in the multiplicity of infection. Consistent with the continuous decline of malaria incidence in the GMS over time, there were also increases in multilocus linkage disequilibrium, suggesting more fragmented and increasingly inbred parasite populations. There were considerable genetic differentiation and sub-division among the four tested populations. Temporal genetic differentiation was observed at each site ( F ST = 0.081 at the CMB and F ST = 0.133 at the TMB). Various degrees of clustering were evident between the older parasite samples collected in 2004 at the CMB with the 2016 CMB and 2012 TMB populations, suggesting some of these parasites had shared ancestry. In contrast, the 2015 TMB population was genetically distinctive, which may reflect a process of population replacement. Whereas the effective population size ( N e ) at the CMB showed a decrease from 4979 in 2004 to 3052 in 2016 with the infinite allele model, the N e at the TMB experienced an increase from 6289 to 10259. Conclusions With enhanced control efforts on malaria, P. vivax at the TMB and CMB showed considerable spatial and temporal differentiation, but the presence of large P. vivax reservoirs still sustained genetic diversity and transmission. These findings provide new insights into P. vivax transmission dynamics and population structure in these border areas of the GMS. Coordinated and integrated control efforts on both sides of international borders are essential to reach the goal of regional malaria elimination.

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“…The CMB area has been traditionally malaria hyperendemic with both P. falciparum and P. vivax transmission. Although recent malaria control efforts have sharply reduced the P. falciparum incidence [35], P. vivax incidence remained consistently high and even experienced outbreaks in recent years [9,36]. In the CMB, 50 samples were collected in 2004 to represent the parasite population prior to the implementation of malaria elimination measures, while 52 samples collected in 2016 represented the parasites after scaling-up of malaria control.…”

Section: Study Sites and P Vivax Clinical Samplesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Evolution of Plasmodium vivax populations in border areas of the Greater Mekong Subregion during malaria elimination

Li¹,

Yan

et al. 2019

Preprint

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BackgroundCountries within the Greater Mekong Subregion (GMS) of Southeast Asia have committed to eliminating malaria by 2030. Although malaria situation has greatly improved, Plasmodium vivax remains at international border regions. Therefore, to gain a better understanding of transmission dynamics, knowledge on the evolution of P. vivax populations after the scale-up of control interventions will guide more effective targeted control efforts. MethodsWe investigated genetic diversity and population structures in 206 longitudinally collected P. vivax clinical samples in two international border areas at the China-Myanmar border (CMB, n=50 in 2004 and n=52 in 2016) and western Thailand border (n=50 in 2012 and n=54 in 2015). Parasites were genotyped using 10 microsatellite markers. ResultsDespite intensified control efforts, genetic diversity in the four populations remained high (HE = 0.66-0.86). The proportions of polyclonal infections showed substantial decreases to 23.7 and 30.7% in the CMB and western Thailand, respectively, with corresponding decreases in the multiplicity of infection. Consistent with the shrinking map of malaria transmission in the GMS over time, there were also increases in multilocus linkage disequilibrium, suggesting of more fragmented and increasingly inbred parasite populations. There were considerable genetic differentiation and subdivision with the four tested populations. Various degrees of clustering were evident between the older parasite samples collected in 2004 at the CMB with the 2016 CMB and 2012 Thailand populations, suggesting some of these parasites had shared ancestry. In contrast, the 2015 Thailand population was genetically distinctive, which may reflect a process of population replacement. The moderately large effective population sizes and proportions of polyclonal infections highlight the necessity of further coordinated and integrated control efforts on both sides of the borders in the pursuit of malaria elimination. ConclusionsWith enhanced control efforts on malaria elimination, P. vivax population in the GMS has fragmented into a limited number of clustered foci, but the presence of large P. vivax reservoirs still sustains genetic diversity and transmission. These findings provide new insights into P. vivax transmission dynamics and population structure in this area.

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Increasing trends of malaria in a border area of the Greater Mekong Subregion

Cited by 44 publications

References 18 publications

Dynamics of Plasmodium vivax populations in border areas of the Greater Mekong sub-region during malaria elimination

Dynamics of Plasmodium vivax populations in border areas of the Greater Mekong sub-region during malaria elimination

Dynamics of Plasmodium vivax populations in border areas of the Greater Mekong Sub-region during malaria elimination

Evolution of Plasmodium vivax populations in border areas of the Greater Mekong Subregion during malaria elimination

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