Abstract
Malaysia has a national goal to eliminate malaria by 2020. Understanding the genetic diversity of malaria parasites in residual transmission foci can provide invaluable information which may inform the intervention strategies used to reach elimination targets. This study was conducted to determine the genetic diversity level of P. falciparum isolates in malaria residual foci areas of Sabah. Malaria active case detection was conducted in Kalabakan and Kota Marudu. All individuals in the study sites were screened for malaria infection by rapid diagnostic test. Blood from P. falciparum-infected individuals were collected on filter paper prior to DNA extraction. Genotyping was performed using merozoite surface protein-1 (MSP-1), merozoite surface protein-2 (MSP-2), glutamate rich protein (GLURP) and 10 neutral microsatellite loci markers. The size of alleles, multiplicity of infection (MOI), mean number of alleles (Na), expected heterozygosity (He), linkage disequilibrium (LD) and genetic differentiation (FST) were determined. In Kalabakan, the MSP-1 and MSP-2 alleles were predominantly K1 and FC27 family types, respectively. The GLURP genotype VI (751–800 bp) was predominant. The MOI for MSP-1 and MSP-2 were 1.65 and 1.20, respectively. The Na per microsatellite locus was 1.70. The He values for MSP-1, MSP-2, GLURP and neutral microsatellites were 0.17, 0.37, 0.70 and 0.33, respectively. In Kota Marudu, the MSP-1 and MSP-2 alleles were predominantly MAD20 and 3D7 family types, respectively. The GLURP genotype IV (651–700 bp) was predominant. The MOI for both MSP-1 and MSP-2 was 1.05. The Na per microsatellite locus was 3.60. The He values for MSP-1, MSP-2, GLURP and neutral microsatellites were 0.24, 0.25, 0.69 and 0.30, respectively. A significant LD was observed in Kalabakan (0.495, p<0.01) and Kota Marudu P. falciparum populations (0.601, p<0.01). High genetic differentiation between Kalabakan and Kota Marudu P. falciparum populations was observed (FST = 0.532). The genetic data from the present study highlighted the limited diversity and contrasting genetic pattern of P. falciparum populations in the malaria declining areas of Sabah.
Highlights
3.3 billion people are at risk of malaria
Up until November 2015, indigenous human malaria cases in Sabah have dropped to 207 cases as compared to 522 cases reported in November 2014 (Vector Borne Disease Control Sector, Ministry of Health, Malaysia, 2015)
A total of 4257 individuals were screened for malaria infection in both study areas
Summary
3.3 billion people are at risk of malaria. In 2015, the number of new malaria cases reached 214 million and malaria deaths were estimated to reach 438,000 [1]. Between 2000 and 2015, malaria incidence and mortality rates decreased worldwide by 37% and 60%, respectively Scaling up interventions such as the widespread usage of insecticide-treated bed nets (ITN), indoor residual spraying (IRS), larval control, improved diagnostic testing and treatment by artemisinin combination therapy (ACT) have contributed to the decrease in malaria cases worldwide. During the implementation of the National Malaria Elimination Plan (2011-current), indigenous human malaria cases were further decreased to only 606 cases in 2014 (Vector Borne Disease Control Sector, Ministry of Health, 2014). East Malaysia, contributed 93% (561 cases) of indigenous human malaria cases in 2014 (Vector Borne Disease Control Sector, Ministry of Health, Malaysia, 2014). Up until November 2015, indigenous human malaria cases in Sabah have dropped to 207 cases as compared to 522 cases reported in November 2014 (Vector Borne Disease Control Sector, Ministry of Health, Malaysia, 2015). On the lead up to malaria elimination, understanding the genetic diversity and population structure of the residual malaria parasite populations is crucial to guide monitoring and evaluation of malaria control strategies and antimalarial interventions
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