Your search found 8 records
1 Schousboe, M. L.; Rajakaruna, R. S.; Salanti, A.; Hapuarachchi, H. C.; Galappaththy, G. N. L.; Bygbjerg, I. C.; Amerasinghe, Priyanie; Konradsen, F.; Alifrangis, M.. 2007. Island-wide diversity in single nucleotide polymorphisms of the Plasmodium vivax dihydrofolate reductase and dihydropteroate synthetase genes in Sri Lanka. Malaria Journal, 6(28). 6p.
(Location: IWMI HQ Call no: IWMI 614.532 G744 SCH Record No: H039911)
2 Rajakaruna, R. S.; Weerasinghe, M.; Alifrangis, M.; Amerasinghe, Priyanie; Konradsen, F. 2006. The role of private drug vendors as malaria treatment providers in selected malaria endemic areas of Sri Lanka. Journal of Vector Borne Diseases, 43:58-65.
Malaria ; Waterborne diseases ; Medicines ; Drugs / Sri Lanka / Anuradhapura / Ampara / Vavuniya / Mannar / Moneragala / Hambantota / Badulla
(Location: IWMI-HQ Call no: IWMI 616.9362 G744 RAJ Record No: H039914)
3 Amerasinghe, Priyanie H.; Alifrangis, M.; van der Hoek, Wim; Wirtz, R. A.; Amerasinghe, Felix P.; Konradsen, Flemming. 2005. Optimizing malarial epidemiological studies in areas of low transmission. Southeast Asian Journal of Tropical Medicine and Public Health, 36(5):1079-1084.
Malaria ; Epidemics ; Waterborne diseases ; Analysis ; Surveys ; Villages / Sri Lanka / Mahameegaswewa
(Location: IWMI HQ Call no: IWMI 614.532 G744 AME Record No: H041472)
Malaria risk factor studies have traditionally used microscopy readings of blood slides as the measure of malaria infection in humans, although alternatives are available. There is the need for an assessment of how the use of these alternative diagnostic approaches will influence the efficiency and significance of epidemiological studies. In an area of Sri Lanka with known risk factors for malaria, two cross-sectional surveys were done at the start and at the peak of transmission season. Microscopy was compared with enzyme-linked immunosorbent assays (ELISA) and polymerase chain reaction (PCR). The major risk factor in this area was the location of houses relative to confirmed vector breeding sites. At the peak of the transmission season, the results pointed in the same direction, irrespective of the diagnostic method used. However, the importance of distance from the breeding site was not statistically significant when microscopy was used, which can be explained by the lower prevalence of microscopy positivity in comparison to the prevalence of ELISAand PCR-positivity. This study suggests that in low-transmission areas, such as Sri Lanka, smaller sample sizes can be used for epidemiological research studies using PCR instead of microscopy to estimate parasite prevalence. This efficiency gain has to be weighed against the higher cost and complexity of the PCR. PCR cannot replace microscopy as the standard diagnostic procedure at the field level. ELISA is not directly comparable with microscopy and PCR but it can also be a useful tool in malaria epidemiological studies. This study indicates that cross-sectional surveys are only efficient if they take place during peak transmission season. Cross sectional surveys currently implemented by the Sri Lankan government in response to local malaria outbreaks can form the basis for valid epidemiological studies and be used for the generation of malaria risk maps if samples were also analyzed using PCR.
4 Rajakaruna, R. S.; Amerasinghe, Priyanie H.; Galappaththy, G. N. L.; Konradsen, F.; Briet, Olivier J. T.; Alifrangis, M.. 2008. Current status of malaria and anti-malarial drug resistance in Sri Lanka. Ceylon Journal of Science (Biological Sciences), 37(1):15-22.
(Location: IWMI HQ Call no: IWMI 614.532 G744 RAJ, PER Record No: H041484)
http://www.sljol.info/index.php/CJSBS/article/viewPDFInterstitial/493/531
https://vlibrary.iwmi.org/pdf/H041484.pdf
https://vlibrary.iwmi.org/pdf/H041484.pdf
Even though malaria continues to cause high morbidity and mortality in most of the malaria endemic countries in the world, it is currently not a major health problem in Sri Lanka. Despite the low malaria incidence, the development and spread of anti-malarial drug resistance, combined with a recent increase in the armed conflict hindering provision of effective health services will make it difficult to control malaria in Sri Lanka. Since chloroquine (CQ) resistant Plasmodium falciparum was first reported from Dambulla area in 1984, the number has increased to more than 50% observed in vivo from various endemic areas. In concordance with this, single nucleotide polymorphisms (SNPs) in genes of P. falciparum responsible for CQ resistance are present. A limited number of trials have investigated the efficacy of the second line drug, sulfadoxine/ pyrimethamine (SP) against P. falciparum and a few cases of resistance have been reported. Moreover, SNPs in P. falciparum genes responsible for SP resistance are present and may constitute a sign of evolving SP resistance development. For P. vivax, drug resistance is not yet recorded as a problem in Sri Lanka, however the prevalence of SP resistant SNPs in P. vivax populations seems high and may pose a risk despite that SP is not used directly against P. vivax infections. Continuous monitoring of drug efficacy in vivo, as well by measuring the prevalence of SNPs related to drug resistance are major issues to be addressed.
5 Gunawardena, S.; Karunaweera, N. D.; Ferreira, M. U.; Phone-Kyaw, M.; Pollack, R. J.; Alifrangis, M.; Rajakaruna, R. S.; Konradsen, F.; Amerasinghe, Priyanie H.; Schousboe, M. L.; Galappaththy, G. N. L.; Abeyasinghe, R. R.; Hartl, D. L.; Wirth, D. F. 2010. Geographic structure of Plasmodium vivax: microsatellite analysis of parasite populations from Sri Lanka, Myanmar, and Ethiopia. American Journal of Tropical Medicine and Hygiene, 82(2):235-242. [doi: https://doi.org/10.4269/ajtmh.2010.09-0588]
Genetic variation ; Plasmodium vivax ; Parasites ; Public health ; Waterborne diseases ; Malaria ; Satellite observation ; Analysis / Sri Lanka / Myanmar / Ethiopia
(Location: IWMI HQ Call no: e-copy only Record No: H044535)
(1.07 MB) (1.07MB)
Genetic diversity and population structure of Plasmodium vivax parasites can predict the origin and spread of novel variants within a population enabling population specific malaria control measures. We analyzed the genetic diversity and population structure of 425 P. vivax isolates from Sri Lanka, Myanmar, and Ethiopia using 12 trinucleotide and tetranucleotide microsatellite markers. All three parasite populations were highly polymorphic with 3–44 alleles per locus. Approximately 65% were multiple-clone infections. Mean genetic diversity ( H E ) was 0.7517 in Ethiopia, 0.8450 in Myanmar, and 0.8610 in Sri Lanka. Significant linkage disequilibrium was maintained. Population structure showed two clusters (Asian and African) according to geography and ancestry. Strong clustering of outbreak isolates from Sri Lanka and Ethiopia was observed. Predictive power of ancestry using two-thirds of the isolates as a model identified 78.2% of isolates accurately as being African or Asian. Microsatellite analysis is a useful tool for mapping short-term outbreaks of malaria and for predicting ancestry.
6 Schousboe, M. L.; Rajakaruna, R. S.; Amerasinghe, Priyanie.; Konradsen, F.; Ord, R.; Pearce, R.; Bygbjerg, C.; Roper, C.; Alifrangis, M.. 2011. Analysis of polymorphisms in the merozoite surface protein-3a gene and two microsatellite loci in Sri Lankan Plasmodium vivax: evidence of population substructure in Sri Lanka. American Journal of Tropical Medicine and Hygiene, 85(6):994-1001. [doi: https://doi.org/10.4269/ajtmh.2011.11-0338]
Malaria ; Plasmodium vivax ; Population ; Public health ; Polymorphism ; Satellite surveys ; Statistical methods ; Genetic variation / Sri Lanka
(Location: IWMI HQ Call no: e-copy only Record No: H044603)
(0.59 MB)
The geographical distribution of genetic variation in Plasmodium vivax samples ( N = 386) from nine districts across Sri Lanka is described using three markers; the P. vivax merozoite surface protein -3a ( Pvmsp -3a) gene, and the two microsatellites m1501 and m3502. At Pvmsp -3a, 11 alleles were found with an expected heterozygosity (H e ) of 0.81, whereas at m1501 and m3502, 24 alleles (H e = 0.85) and 8 alleles (H e = 0.74) were detected, respectively. Overall, 95 unique three locus genotypes were detected among the 279 samples positive at all three loci (H e = 0.95). Calculating the pairwise fixation index ( F ST ) revealed statistically significant population structure. The presence of identical 2-loci microsatellite genotypes in a significant proportion of samples revealed local clusters of closely related isolates contributing to strong linkage disequilibrium between marker alleles. The results show evidence of high genetic diversity and possible population substructure of P. vivax populations in Sri Lanka.
7 Schousboe, M. L.; Ranjitkar, S.; Rajakaruna, R. S.; Amerasinghe, Priyanie; Konradsen, F.; Morales, F.; Ord, R.; Pearce, R.; Leslie, T.; Rowland, M.; Gadalla, N; Bygbjerg, C.; Alifrangis, M.; Roper, C. 2014. Global and local genetic diversity at two microsatellite loci in Plasmodium vivax parasites from Asia, Africa and South America. Malaria Journal, 13:1-9. [doi: https://doi.org/10.1186/1475-2875-13-392]
Genetic variation ; Plasmodium vivax ; Parasites ; Loci ; Malaria ; Public health ; Microsatellites / Asia / Africa / South America / Sri Lanka / Pakistan / Afghanistan / Nepal / Sudan / Venezuela / Ecuador
(Location: IWMI HQ Call no: e-copy only Record No: H047016)
http://www.malariajournal.com/content/pdf/1475-2875-13-392.pdf
https://vlibrary.iwmi.org/pdf/H047016.pdf
https://vlibrary.iwmi.org/pdf/H047016.pdf
(0.34 MB) (349 KB)
Background: Even though Plasmodium vivax has the widest worldwide distribution of the human malaria species and imposes a serious impact on global public health, the investigation of genetic diversity in this species has been limited in comparison to Plasmodium falciparum. Markers of genetic diversity are vital to the evaluation of drug and vaccine efficacy, tracking of P. vivax outbreaks, and assessing geographical differentiation between parasite populations.
Methods: The genetic diversity of eight P. vivax populations (n = 543) was investigated by using two microsatellites (MS), m1501 and m3502, chosen because of their seven and eight base-pair (bp) repeat lengths, respectively. These were compared with published data of the same loci from six other P. vivax populations.
Results: In total, 1,440 P. vivax samples from 14 countries on three continents were compared. There was highest heterozygosity within Asian populations, where expected heterozygosity (He) was 0.92-0.98, and alleles with a high repeat number were more common. Pairwise FST revealed significant differentiation between most P. vivax populations, with the highest divergence found between Asian and South American populations, yet the majority of the diversity (~89%) was found to exist within rather than between populations.
Conclusions: The MS markers used were informative in both global and local P. vivax population comparisons and their seven and eight bp repeat length facilitated population comparison using data from independent studies. A complex spatial pattern of MS polymorphisms among global P. vivax populations was observed which has potential utility in future epidemiological studies of the P. vivax parasite.
Methods: The genetic diversity of eight P. vivax populations (n = 543) was investigated by using two microsatellites (MS), m1501 and m3502, chosen because of their seven and eight base-pair (bp) repeat lengths, respectively. These were compared with published data of the same loci from six other P. vivax populations.
Results: In total, 1,440 P. vivax samples from 14 countries on three continents were compared. There was highest heterozygosity within Asian populations, where expected heterozygosity (He) was 0.92-0.98, and alleles with a high repeat number were more common. Pairwise FST revealed significant differentiation between most P. vivax populations, with the highest divergence found between Asian and South American populations, yet the majority of the diversity (~89%) was found to exist within rather than between populations.
Conclusions: The MS markers used were informative in both global and local P. vivax population comparisons and their seven and eight bp repeat length facilitated population comparison using data from independent studies. A complex spatial pattern of MS polymorphisms among global P. vivax populations was observed which has potential utility in future epidemiological studies of the P. vivax parasite.
8 Schousboe, M. L.; Ranjitkar, S.; Rajakaruna, R. S.; Amerasinghe, Priyanie H.; Morales, F.; Pearce, R.; Ord, R.; Leslie, T.; Rowland, M.; Gadalla, N. B.; Konradsen, F.; Bygbjerg, C.; Roper, C.; Alifrangis, M.. 2015. Multiple origins of mutations in the mdr1 gene—a putative marker of chloroquine resistance in P. vivax. PLoS Neglected Tropical Diseases, 9(11):1-17. [doi: https://doi.org/10.1371/journal.pntd.0004196]
Medical sciences ; Mutation ; Malaria ; Drugs ; Codons ; Genes ; DNA ; Microsatellites / Pakistan / Afghanistan / Sri Lanka / Nepal / Sudan / Sao Tome / Ecuador
(Location: IWMI HQ Call no: e-copy only Record No: H047288)
http://www.plosntds.org/article/fetchObject.action?uri=info:doi/10.1371/journal.pntd.0004196&representation=PDF
https://vlibrary.iwmi.org/pdf/H047288.pdf
https://vlibrary.iwmi.org/pdf/H047288.pdf
(1.19 MB) (1.19 MB)
Background
Chloroquine combined with primaquine has been the ecommended antimalarial treatment of Plasmodium vivax malaria infections for six decades but the efficacy of this treatment regimen is threatened by chloroquine resistance (CQR). Single nucleotide polymorphisms (SNPs) in the multidrug resistance gene, Pvmdr1 are putative determinants of CQR but the extent of their emergence at population level remains to be explored.
Objective
In this study we describe the prevalence of SNPs in the Pvmdr1 among samples collected in seven P. vivax endemic countries and we looked for molecular evidence of drug selection by characterising polymorphism at microsatellite (MS) loci flanking the Pvmdr1 gene.
Methods
We examined the prevalence of SNPs in the Pvmdr1 gene among 267 samples collected from Pakistan, Afghanistan, Sri Lanka, Nepal, Sudan, Sao Tome and Ecuador. We measured and diversity in four microsatellite (MS) markers flanking the Pvmdr1 gene to look evidence of selection on mutant alleles.
Results
SNP polymorphism in the Pvmdr1 gene was largely confined to codons T958M, Y976F and F1076L. Only 2.4% of samples were wildtype at all three codons (TYF, n = 5), 13.3% (n =28) of the samples were single mutant MYF, 63.0% of samples (n = 133) were double mutant MYL, and 21.3%(n = 45) were triple mutant MFL. Clear geographic differences in the prevalence of these Pvmdr mutation combinations were observed. Significant linkage disequilibrium (LD) between Pvmdr1 and MS alleles was found in populations sampled in Ecuador, Nepal and Sri Lanka, while significant LD between Pvmdr1 and the combined 4 MS locus haplotype was only seen in Ecuador and Sri Lanka. When combining the 5 loci, high level diversity, measured as expected heterozygosity (He), was seen in the complete sample set (He = 0.99), while He estimates for individual loci ranged from 0.00–0.93. Although Pvmdr1 haplotypes were not consistently associated with specific flanking MS alleles, there was significant differentiation between geographic sites which could indicate directional selection through local drug pressure.
Conclusions
Our observations suggest that Pvmdr1 mutations emerged independently on multiple occasions even within the same population. In Sri Lanka population analysis at multiple sites showed evidence of local selection and geographical dispersal of Pvmdr1 mutations between sites.
Chloroquine combined with primaquine has been the ecommended antimalarial treatment of Plasmodium vivax malaria infections for six decades but the efficacy of this treatment regimen is threatened by chloroquine resistance (CQR). Single nucleotide polymorphisms (SNPs) in the multidrug resistance gene, Pvmdr1 are putative determinants of CQR but the extent of their emergence at population level remains to be explored.
Objective
In this study we describe the prevalence of SNPs in the Pvmdr1 among samples collected in seven P. vivax endemic countries and we looked for molecular evidence of drug selection by characterising polymorphism at microsatellite (MS) loci flanking the Pvmdr1 gene.
Methods
We examined the prevalence of SNPs in the Pvmdr1 gene among 267 samples collected from Pakistan, Afghanistan, Sri Lanka, Nepal, Sudan, Sao Tome and Ecuador. We measured and diversity in four microsatellite (MS) markers flanking the Pvmdr1 gene to look evidence of selection on mutant alleles.
Results
SNP polymorphism in the Pvmdr1 gene was largely confined to codons T958M, Y976F and F1076L. Only 2.4% of samples were wildtype at all three codons (TYF, n = 5), 13.3% (n =28) of the samples were single mutant MYF, 63.0% of samples (n = 133) were double mutant MYL, and 21.3%(n = 45) were triple mutant MFL. Clear geographic differences in the prevalence of these Pvmdr mutation combinations were observed. Significant linkage disequilibrium (LD) between Pvmdr1 and MS alleles was found in populations sampled in Ecuador, Nepal and Sri Lanka, while significant LD between Pvmdr1 and the combined 4 MS locus haplotype was only seen in Ecuador and Sri Lanka. When combining the 5 loci, high level diversity, measured as expected heterozygosity (He), was seen in the complete sample set (He = 0.99), while He estimates for individual loci ranged from 0.00–0.93. Although Pvmdr1 haplotypes were not consistently associated with specific flanking MS alleles, there was significant differentiation between geographic sites which could indicate directional selection through local drug pressure.
Conclusions
Our observations suggest that Pvmdr1 mutations emerged independently on multiple occasions even within the same population. In Sri Lanka population analysis at multiple sites showed evidence of local selection and geographical dispersal of Pvmdr1 mutations between sites.
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