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Prevalence of Plasmodium vivax VK210 and VK247 subtype in Myanmar
Tong-Soo Kim, Hyung-Hwan Kim, Sun-Sim Lee, Byoung-Kuk Na, Khin Lin, Shin-Hyeong Cho, Yoon-Joong Kang, Do-Kyung Kim, Youngjoo Sohn, Hyuck Kim, Hyeong-Woo Lee
Malaria Journal , 2010, DOI: 10.1186/1475-2875-9-195
Abstract: The existence of malaria parasites in blood samples was determined by microscopic examination, polymerase chain reaction (PCR) and DNA hybridization assays. To test for antibodies against P. vivax and Plasmodium falciparum in blood samples, an indirect immunofluorescence antibody test (IFAT) was performed using asexual blood antigens. An enzyme-linked immunosorbent assay with synthetic VK210 and VK247 antigens was carried out to discriminate between the P. vivax subtypes.By thick smear examination, 73 (n = 100) patients were single infected with P. vivax, one with P. falciparum and 13 with both species. By thin smear, 53 patients were single infected with P. vivax, eight with only P. falciparum and 16 with both. Most of the collected blood samples were shown to be P. vivax positive (n = 95) by PCR. All cases that were positive for P. falciparum by PCR (n = 43) were also positive for P. vivax. However, 52 cases were single infected with P. vivax. IFAT showed antibody titres from 1:32 to 1:4,096. Additionally, using specific antibodies for VK210 and VK247, ELISA showed that 12 patients had antibodies for only the VK210 subtype, 4 patients had only VK247 subtype antibodies and 21 patients had antibodies for both subtypes. Using a DNA hybridization test, 47 patients were infected with the VK210 type, one patient was infected with VK247 and 23 patients were infected with both subtypes.The proportion of the VK247 subtype in Myanmar was 43.1% (n = 25) among 58 positive cases by serodiagnosis and 25.6% (n = 24) among 94 positive cases by genetic diagnosis. In both diagnostic methods, the infection status of malaria patients is highly diverse with respect to malaria species, and multiple clonal infections are prevalent in Myanmar. Therefore, the complexity of the infection should be considered carefully when diagnosing malaria in Myanmar.Plasmodium vivax, a causative agent of relapsing benign tertian malaria, is the second most important malaria-causing species and afflicts
Directly-observed therapy (DOT) for the radical 14-day primaquine treatment of Plasmodium vivax malaria on the Thai-Myanmar border
Rie Takeuchi, Saranath Lawpoolsri, Mallika Imwong, Jun Kobayashi, Jaranit Kaewkungwal, Sasithon Pukrittayakamee, Supalap Puangsa-art, Nipon Thanyavanich, Wanchai Maneeboonyang, Nicholas PJ Day, Pratap Singhasivanon
Malaria Journal , 2010, DOI: 10.1186/1475-2875-9-308
Abstract: A randomized trial was conducted from May 2007 to January 2009 in a low malaria transmission area along the Thai-Myanmar border. Patients aged ≥ 3 years diagnosed with P. vivax by microscopy, were recruited. All patients were treated with the national standard regimen of chloroquine for three days followed by primaquine for 14 days. Patients were randomized to receive DOT or self-administered therapy (SAT). All patients were followed for three months to check for any reappearance of P. vivax.Of the 216 patients enrolled, 109 were randomized to DOT and 107 to SAT. All patients recovered without serious adverse effects. The vivax reappearance rate was significantly lower in the DOT group than the SAT group (3.4/10,000 person-days vs. 13.5/10,000 person-days, p = 0.021). Factors related to the reappearance of vivax malaria included inadequate total primaquine dosage received (< 2.75 mg/kg), duration of fever ≤ 2 days before initiation of treatment, parasite count on admission ≥ 10,000/μl, multiple P. vivax-genotype infection, and presence of P. falciparum infection during the follow-up period.Adherence to the 14-day primaquine regimen is important for the radical cure of P. vivax malaria infection. Implementation of DOT reduces the reappearance rate of the parasite, and may subsequently decrease P. vivax transmission in the area.Globally, over 3 billion people live in areas at risk of malaria infection; about one billion of these live in countries outside Africa, where malaria transmission is low and Plasmodium vivax is most prevalent [1,2]. Unlike Plasmodium falciparum, P. vivax infection rarely develops into complicated malaria and death is unusual. However, P. vivax has a dormant stage (the hypnozoite) that persists in the human liver and may cause relapse weeks, months, or even years later. Therefore, P. vivax infection is considered to have greater impact on morbidity than mortality, resulting in significant social and economic burdens [1]. Moreover, it is very di
Monitoring of clinical efficacy and in vitro sensitivity of Plasmodium vivax to chloroquine in area along Thai Myanmar border during 2009-2010
Poonuch Muhamad, Ronnatrai Ruengweerayut, Wanna Chacharoenkul, Kanchana Rungsihirunrat, Kesara Na-Bangchang
Malaria Journal , 2011, DOI: 10.1186/1475-2875-10-44
Abstract: The study was conducted at Mae Tao clinic for migrant workers, Tak Province during March 2008 - August 2009. A total of 130 patients (17 Thais and 113 Burmeses; 64 males and 66 females) with mono-infection of P. vivax malaria, aged between 15-60 years and weighing more than 40 kg, were included in the study. Patients received treatment with chloroquine (2,000 mg chloroquine phosphate over three days) and the anti-relapse drug primaquine (15 mg for 14 days). In vitro sensitivity of P. vivax isolates was evaluated by schizont maturation inhibition assay.All patients showed satisfactory response to treatment. The cure rate was virtually 100% within the follow-up period of 42 days. Neither recurrence of P. vivax parasitaemia nor appearance of P. falciparum occurred during the investigation period. In vitro data showed a stable sensitivity of chloroquine in this area since 2006. Geometric mean and median (95% CI) values of IC50 for chloroquine were 100.1 and 134.7 (1.1-264.9) nM, respectively.In vivo results suggest that the standard regimen of chloroquine was still very effective for the treatment of blood infections with P. vivax in the Thai-Myanmar border area. In vitro sensitivity data however, raise the possibility of potential advent of resistance in the future. Regular monitoring of the chloroquine sensitivity of P. vivax is essential to facilitate the early recognition of treatment failures and to expedite the formulation of appropriate changes to the drug policy.Plasmodium vivax is responsible for approximately 70 to 80 million cases of malaria worldwide annually, and is the major cause of human malaria in parts of Pacific region and Central and South America [1]. The disease is rarely life-threatening, but morbidity from prolonged illness and the possibility of relapses from a persistent hepatic form (hypnozoite) are of major concern. Plasmodium vivax can only infect reticulocytes, which limits parasitaemia, usually to densities lower than 100,000/ml blood. The
Genetic polymorphism and natural selection of Duffy binding protein of Plasmodium vivax Myanmar isolates
Hye-Lim Ju, Jung-Mi Kang, Sung-Ung Moon, Jung-Yeon Kim, Hyeong-Woo Lee, Khin Lin, Woon-Mok Sohn, Jin-Soo Lee, Tong-Soo Kim, Byoung-Kuk Na
Malaria Journal , 2012, DOI: 10.1186/1475-2875-11-60
Abstract: Fifty-four P. vivax infected blood samples collected from patients in Myanmar were used. The region flanking PvDBPII was amplified by PCR, cloned into Escherichia coli, and sequenced. The polymorphic characters and natural selection of the region were analysed using the DnaSP and MEGA4 programs.Thirty-two point mutations (28 non-synonymous and four synonymous mutations) were identified in PvDBPII among the Myanmar P. vivax isolates. Sequence analyses revealed that 12 different PvDBPII haplotypes were identified in Myanmar P. vivax isolates and that the region has evolved under positive natural selection. High selective pressure preferentially acted on regions identified as B- and T-cell epitopes of PvDBPII. Recombination may also be played a role in the resulting genetic diversity of PvDBPII.PvDBPII of Myanmar P. vivax isolates displays a high level of genetic polymorphism and is under selective pressure. Myanmar P. vivax isolates share distinct types of PvDBPII alleles that are different from those of other geographical areas. These results will be useful for understanding the nature of the P. vivax population in Myanmar and for development of PvDBPII-based vaccine.Plasmodium vivax Duffy binding protein (PvDBP) is one of the erythrocyte-binding proteins, which belongs to the large erythrocyte binding protein family [1]. PvDBP is expressed on the merozoite of P. vivax and plays an essential role in erythrocyte invasion of the parasite by mediating irreversible binding with its corresponding receptor, the duffy antigen receptor for chemokines (DARC), on the surface of erythrocytes [1-4]. Similar to other plasmodial proteins known to participate in such processes, PvDBP is suggested to be an important vaccine candidate antigen, because it elicits strong immune responses in humans [5,6]. Experimental evidences that antibodies against PvDBP inhibit the interaction of this protein with DARC in vitro and block the invasion of P. vivax into human erythrocytes also support
Longitudinal study of Plasmodium falciparum and Plasmodium vivax in a Karen population in Thailand
Waraphon Phimpraphi, Richard E Paul, Surapon Yimsamran, Supalarp Puangsa-art, Nipon Thanyavanich, Wanchai Maneeboonyang, Sutthiporn Prommongkol, Samarn Sornklom, Wutthichai Chaimungkun, Irwin F Chavez, Herve Blanc, Sornchai Looareesuwan, Anavaj Sakuntabhai, Pratap Singhasivanon
Malaria Journal , 2008, DOI: 10.1186/1475-2875-7-99
Abstract: A clinical malaria case treatment programme was carried out over a decade in a Karen community composed of seven hamlets on the Thai-Myanmar border.From 1994 to 2004, prevalence rates of both P. falciparum and P. vivax decreased by 70–90% in six of the seven study hamlets, but were unchanged in one hamlet. Overall, incidence rates decreased by 72% and 76% for P. falciparum and P. vivax respectively over the period 1999–2004. The age-incidence and prevalence curves suggested that P. vivax was more transmissible than P. falciparum despite a greater overall burden of infection with P. falciparum. Male gender was associated with increased risk of clinical presentation with either parasite species. Children (< 15 years old) had an increased risk of presenting with P. vivax but not P. falciparum.There was a considerable reduction in incidence rates of both P. vivax and P. falciparum over a decade following implementation of a case treatment programme. The concern that intervention methods would inadvertently favour one species over another, or even lead to an increase in one parasite species, does not appear to be fulfilled in this case.Over the last decade in Thailand, a concerted programme at the national level of clinical case treatment coupled with vector control programmes has led to a greatly reduced burden of malaria [1], restricting malaria transmission to the border provinces. The Tak Malaria Initiative (TMI) sought to address the malaria problem in one of these border provinces, Tak, implementing a system of early diagnosis and treatment with mefloquine-artesunate combination therapy [2]. This initiative proved most successful in reducing morbidity and mortality of P. falciparum but had seemingly little impact on P. vivax. Plasmodium vivax accounts for over half of all malaria infections outside Africa and in 2002 the Multilateral Initiative on Malaria convened a special conference, "Vivax Malaria Research: 2002 and Beyond" [3]. The conference highlighted the di
Country-wide assessment of the genetic polymorphism in Plasmodium falciparum and Plasmodium vivax antigens detected with rapid diagnostic tests for malaria
Natacha Mariette, Céline Barnadas, Christiane Bouchier, Magali Tichit, Didier Ménard
Malaria Journal , 2008, DOI: 10.1186/1475-2875-7-219
Abstract: A country-wide assessment of polymorphism of the PfHRP2, PfHRP3, pLDH and aldolase antigens was carried out in 260 Plasmodium falciparum and 127 Plasmodium vivax isolates, by sequencing the genes encoding these antigens in parasites originating from the various epidemiological strata for malaria in Madagascar.Higher levels of polymorphism were observed for the pfhrp2 and pfhrp3 genes than for the P. falciparum and P. vivax aldolase and pldh genes. Pfhrp2 sequence analysis predicted that 9% of Malagasy isolates would not be detected at parasite densities ≤ 250 parasites/μl (ranging from 6% in the north to 14% in the south), although RDTs based on PfHRP2 detection are now recommended in Madagascar.These findings highlight the importance of training of health workers and the end users of RDTs in the provision of information about the possibility of false-negative results for patients with clinical symptoms of malaria, particularly in the south of Madagascar.Since the emergence and spread of Plasmodium falciparum parasites resistant to inexpensive anti-malarial drugs, such as chloroquine (CQ) and sulphadoxine-pyrimethamine (SP), routine malaria case management has changed in endemic countries, such as Madagascar. Malaria diagnosis in these areas – particularly in zones not well covered by healthcare facilities – was entirely based on clinical examination, with CQ widely administered for any fever with no obvious alternative cause [1-3]. Since the introduction of more effective, more expensive anti-malarial drug combinations, such as artemisinin combination therapy (ACT), the WHO recommends the establishment of an accurate biological diagnosis before treatment and the withdrawal of presumptive anti-malarial treatment for all patients other than children under the age of five years in hyperendemic areas. This change in medical practice is now a public health priority in Africa, ensuring that effective anti-malarial drugs are administered only to the patients who need them
Genetic diversity and population structure of genes encoding vaccine candidate antigens of Plasmodium vivax
Stella M Chenet, Lorena L Tapia, Ananias A Escalante, Salomon Durand, Carmen Lucas, David J Bacon
Malaria Journal , 2012, DOI: 10.1186/1475-2875-11-68
Abstract: Genetic variability was assessed in important polymorphic regions of various vaccine candidate antigens in P. vivax among 106 isolates from the Amazon Region of Loreto, Peru. In addition, genetic diversity determined in Peruvian isolates was compared to population studies from various geographical locations worldwide.The structured diversity found in P. vivax populations did not show a geographic pattern and haplotypes from all gene candidates were distributed worldwide. In addition, evidence of balancing selection was found in polymorphic regions of the trap, dbp and ama-1 genes.It is important to have a good representation of the haplotypes circulating worldwide when implementing a vaccine, regardless of the geographic region of deployment since selective pressure plays an important role in structuring antigen diversity.Malaria is one of the major global public health problems that affect most tropical regions of the world. Even though Plasmodium falciparum is the most virulent, it is estimated that Plasmodium vivax produces around 80 to 300 million clinical cases per year [1]. Furthermore, there have been several reports of severe P. vivax malaria cases in the last few years [2-4]. In 2008, 560,221 malaria cases were reported in the Americas [5]; 74.2% of them caused by P. vivax and 25.7% by P. falciparum [1]. About 90% of these malaria cases originated in the Amazon basin shared by Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Venezuela, Suriname and Peru [5], whereas the other 10% was contributed by non-Amazon regions.Developing a vaccine for P. vivax represents a major challenge especially considering the lack of in vitro cultures. Thus, current efforts focus on orthologs of P. falciparum. Over the past four decades, experiments performed in animals and human subjects have led to the development of several Plasmodium vaccine candidates. Antigenic surface proteins such as the Circumsporozoite protein (CSP), Thrombospondin related anonymous protein
Differing Patterns of Selection and Geospatial Genetic Diversity within Two Leading Plasmodium vivax Candidate Vaccine Antigens  [PDF]
Christian M. Parobek ,Jeffrey A. Bailey,Nicholas J. Hathaway,Duong Socheat,William O. Rogers,Jonathan J. Juliano
PLOS Neglected Tropical Diseases , 2014, DOI: 10.1371/journal.pntd.0002796
Abstract: Although Plasmodium vivax is a leading cause of malaria around the world, only a handful of vivax antigens are being studied for vaccine development. Here, we investigated genetic signatures of selection and geospatial genetic diversity of two leading vivax vaccine antigens – Plasmodium vivax merozoite surface protein 1 (pvmsp-1) and Plasmodium vivax circumsporozoite protein (pvcsp). Using scalable next-generation sequencing, we deep-sequenced amplicons of the 42 kDa region of pvmsp-1 (n = 44) and the complete gene of pvcsp (n = 47) from Cambodian isolates. These sequences were then compared with global parasite populations obtained from GenBank. Using a combination of statistical and phylogenetic methods to assess for selection and population structure, we found strong evidence of balancing selection in the 42 kDa region of pvmsp-1, which varied significantly over the length of the gene, consistent with immune-mediated selection. In pvcsp, the highly variable central repeat region also showed patterns consistent with immune selection, which were lacking outside the repeat. The patterns of selection seen in both genes differed from their P. falciparum orthologs. In addition, we found that, similar to merozoite antigens from P. falciparum malaria, genetic diversity of pvmsp-1 sequences showed no geographic clustering, while the non-merozoite antigen, pvcsp, showed strong geographic clustering. These findings suggest that while immune selection may act on both vivax vaccine candidate antigens, the geographic distribution of genetic variability differs greatly between these two genes. The selective forces driving this diversification could lead to antigen escape and vaccine failure. Better understanding the geographic distribution of genetic variability in vaccine candidate antigens will be key to designing and implementing efficacious vaccines.
Human Plasmodium knowlesi infection in Ranong province, southwestern border of Thailand
Natthawan Sermwittayawong, Balbir Singh, Mitsuaki Nishibuchi, Nongyao Sawangjaroen, Varaporn Vuddhakul
Malaria Journal , 2012, DOI: 10.1186/1475-2875-11-36
Abstract: Blood samples collected from 171 Thai and 248 Myanmese patients attending a malaria clinic in Ranong province, Thailand, located near the Myanmar border were investigated for P. knowlesi using nested PCR assays. Positive samples were also investigated by PCR for Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae and Plasmodium ovale, and were confirmed by sequencing the gene encoding the circumsporozoite protein (csp).Two samples, one obtained from a Thai and the other a Myanmese, were positive for P. knowlesi only. Nucleotide sequences of the csp gene derived from these two patients were identical and phylogenetically indistinguishable from other P. knowlesi sequences derived from monkeys and humans. Both patients worked in Koh Song, located in the Kawthoung district of Myanmar, which borders Thailand.This study indicates that transmission of P. knowlesi is occurring in the Ranong province of Thailand or the Kawthoung district of Myanmar. Further studies are required to assess the incidence of knowlesi malaria and whether macaques in these areas are the source of the infections.There are more than 200 species of Plasmodium that infect a variety of hosts, including reptiles, birds, rodents, primates and other mammals [1]. However, only four species (Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae and Plasmodium ovale) are well-known infectious agents that cause malaria in humans. Recently, humans infected with Plasmodium knowlesi, a simian malaria parasite [1], have been described in a number of Southeast Asian countries including Malaysia [2,3], Singapore [4], Myanmar [5], Vietnam [6], Indonesia [7], the Philippines [8] and Thailand [9]. Under the microscope, the early trophozoites of P. knowlesi cannot be distinguished from those of P. falciparum and the other blood stages are identical to P. malariae. Therefore, molecular detection methods are required for the accurate identification of P. knowlesi.In Thailand, the first case of a human P.
Genetic polymorphism of merozoite surface protein-1 and merozoite surface protein-2 in Plasmodium falciparum field isolates from Myanmar
Jung-Mi Kang, Sung-Ung Moon, Jung-Yeon Kim, Shin-Hyeong Cho, Khin Lin, Woon-Mok Sohn, Tong-Soo Kim, Byoung-Kuk Na
Malaria Journal , 2010, DOI: 10.1186/1475-2875-9-131
Abstract: A total of 63 P. falciparum infected blood samples, which were collected from patients attending a regional hospital in Mandalay Division, Myanmar, were used in this study. The regions flanking the highly polymorphic characters, block 2 for MSP-1 and block 3 for MSP-2, were genotyped by allele-specific nested-PCR to analyse the population diversity of the parasite. Sequence analysis of the polymorphic regions of MSP-1 and MSP-2 was also conducted to identify allelic diversity in the parasite population.Diverse allelic polymorphism of MSP-1 and MSP-2 was identified in P. falciparum isolates from Myanmar and most of the infections were determined to be mixed infections. Sequence analysis of MSP-1 block 2 revealed that 14 different alleles for MSP-1 (5 for K1 type and 9 for MAD20 type) were identified. For MSP-2 block 3, a total of 22 alleles (7 for FC27 type and 15 for 3D7 type) were identified.Extensive genetic polymorphism with diverse allele types was identified in MSP-1 and MSP-2 in P. falciparum field isolates from Myanmar. A high level of mixed infections was also observed, as was a high degree of multiplicity of infection.Malaria is a major human health-threatening disease, which resulting in approximately 200-300 million clinical cases and 1-3 million deaths each year worldwide. Plasmodium falciparum causes the most severe form of the disease and is responsible for most malaria morbidity and almost all malaria mortality. Despite enormous efforts for malaria control and prevention, multiple factors, including insecticide resistance in the mosquito vectors, the lack of effective vaccines, and the emergence and rapid spread of drug-resistant strains, are contributing to the global worsening of the malaria situation. Therefore, there is an urgent need for the development of effective malaria vaccine. However, extensive genetic diversity in natural parasite populations is a major obstacle for the development of an effective vaccine against the human malaria parasit
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