Papers by Phonepadith Khattignavong
PLOS Neglected Tropical Diseases, Dec 20, 2017
PLOS Neglected Tropical Diseases, Mar 22, 2018
On July 17, 2016, a 12-year-old Laotian boy living in Bengvilay village, Sanamxay district, Attap... more On July 17, 2016, a 12-year-old Laotian boy living in Bengvilay village, Sanamxay district, Attapeu province (adjacent to Cambodia) in Laos visited Bengvilay Health Center. He manifested malaria-like symptoms and signs such as high fever (40 o C), shivering, and nausea. The patient did not have a history of traveling outside of Attapeu province, Laos. The fever started 3 days before he visited the health center. He was diagnosed as having been infected with Plasmodium vivax malaria by a Rapid Diagnostic Test (RDT) kit (Malaria Ag Pf/Pv, Standard Diagnostics, Republic of Korea) at the health center, and a 3-day course of artemether/lumefantrine was prescribed. The patient recovered after the treatment. Prior to this episode, the patient had been recorded as having 4 previous malaria episodes that were diagnosed by the RDT kit, but detailed information, such as Plasmodium species and symptoms, was not recorded. The family used insecticide-treated bednets inside their home. The family was employed in agriculturally related jobs and occasionally went to the forest to collect foods and other necessities. The patient sometimes accompanied his family to the forest. A finger-prick blood sample was collected on a filter paper (Whatman FTA Classic Cards, GE Healthcare Life Science, United Kingdom) prior to the treatment, and we implemented a molecular approach to confirm the Plasmodium species by PCR and DNA sequencing. We collected 2,698 finger-prick blood samples from malaria patients (positive by microscopy or RDT), including the 12-year-old Laotian boy, on the filter papers from 155 public health care facilities in the 5 southern provinces in Laos from October 2015 through October 2016 for detecting human infection with P. knowlesi. We examined all the blood samples by PCR.
Malaria Journal, Dec 1, 2018
Background: The emergence and transnational spread of artemisinin resistance in Plasmodium falcip... more Background: The emergence and transnational spread of artemisinin resistance in Plasmodium falciparum in the Greater Mekong Sub-region (GMS) is a serious threat to malaria elimination in the region and could present a threat to malaria control in Africa. Recently, the Lao Government adopted the goal of malaria elimination by 2030, for which monitoring of artemisinin-resistant malaria within the country is indispensable. This study's objectives were to assess the distribution of k13 mutations in Laos. Methods: Plasmodium falciparum isolates (n = 1151) were collected from five southern provinces in Laos between 2015 and 2016, and three isolates from the northernmost province bordering China in 2017. Polymorphisms of the k13 gene and two flanking regions were analysed to estimate relationship among the isolates. Results: In the five southern provinces, overall 55.5% of the isolates possessed artemisinin-resistant mutations of the k13 gene (C580Y, P574L, R539T, Y493H). The C580Y was the predominant mutation (87.2%). The frequencies of the k13 mutations were heterogeneous in the five southern provinces, but with a clear tendency showing the highest frequency in the south (72.5%) and to a lower degree when moving northward (28.0%). The three isolates from the Lao-Chinese border also possessed the C580Y mutation. Analysis of the flanking loci demonstrated that these three isolates were genetically very close to resistant strains originating from western Cambodia. Conclusions: Artemisinin resistance was observed to be rapidly increasing and spreading northwards through Laos and has now reached the Chinese border. The Lao and Chinese governments, as well as the international community, should make dedicated efforts to contain the spread of k13 mutations within Laos and in the GMS.
Tropical Medicine and Health, Jan 25, 2019
Background: Although mobile and migrant populations are considered an important group in malaria ... more Background: Although mobile and migrant populations are considered an important group in malaria elimination settings, there is currently a lack of understanding about foreign migrant workers in the Lao People's Democratic Republic (Lao PDR). The present study aimed to document the migration characteristics, positive rate of malaria infection, and preventive and treatment-seeking behavior for malaria among foreign migrant workers in the malaria-endemic districts of Savannakhet province, Lao PDR. Methods: A community-based survey was undertaken in four districts of Savannakhet province between February and June, 2015. Questionnaire-based interviews and blood examinations, including rapid diagnostic tests and PCR assays, were conducted with 391 migrant workers who were registered at local police departments. Results: Most of the study participants were men (75.7%) and Vietnamese (92.6%). The median age (interquartile range) was 31 (25 to 41) years old. Most common occupation was factory worker (47.6%), followed by trader/ shopkeeper (21.5%) and plantation worker/farmer (16.4%). The median length of stay (interquartile range) in the districts was 405 (183 to 1207) days. The majority of the participants (85.9%) had not worked in a province other than the study province, nor had the majority (92.6%) worked in a foreign country other than the Lao PDR. Although most of the participants (62.7%) reportedly used a bed net daily, these nets were mostly conventional untreated ones. No one tested positive for malaria. However, 10.0% of the participants reported a malaria-like illness episode that had occurred in the Lao PDR. The most common measure taken for the episode was to visit a hospital/health center in the Lao PDR, followed by conducting self-medication alone. Forty-one participants reported an experience of working in the forest while living in the Lao PDR. Conclusions: Foreign migrant workers who are registered at local police departments are unlikely to play a major role in maintaining local transmissions and spreading drug-resistant malaria in the study province. However, some of them were involved in forest-related activities, suggesting that these workers are potentially at risk of malaria. The Lao National Malaria Control Program should educate foreign migrant workers about the risk of malaria when living in Lao PDR.
Malaria Journal, Mar 12, 2019
Background: Primaquine is effective against the latent liver stage of Plasmodium vivax. Eliminati... more Background: Primaquine is effective against the latent liver stage of Plasmodium vivax. Eliminating the latent liver stage of P. vivax is one of the necessary conditions to achieve the goal of malaria elimination in Lao People's Democratic Republic (PDR) by 2030. However, people with glucose-6-phosphate dehydrogenase (G6PD) deficiency are at risk of haemolysis when ingesting primaquine. The aim of this study was to detect the prevalence of the G6PD Viangchan variant, which is said to be common in Lao PDR and which can result in severe haemolysis in patients exposed to primaquine. Methods: Blood samples were collected from villagers in three malaria endemic provinces: Champasak and Savannakhet in the south, and Phongsaly in the north. Each blood sample was semi-quantitatively assayed for G6PD enzyme activity using the G6PD Assay Kit-WST Lyophilized (DOJINDO Laboratories, Japan). Blood samples that were found to be G6PD deficient were sequenced to detect G6PD Viangchan mutation. Results: In total, 2043 blood samples were collected from Phongsaly (n = 426, 20.9%), Savannakhet (n = 924, 45.2%), and Champasak (n = 693, 33.9%) provinces in Lao PDR from 2016 to 2017. Of these, 964 (47.2%) were taken from male villagers and 1079 (52.8%) were taken from female villagers. G6PD Viangchan mutation was not detected in Phongsaly province in this study. In Savannakhet province, 48 of the 924 samples (45 males, 3 females) had the G6PD Viangchan mutation (n = 48, 5.2%). In Champasak province, 42 of the 693 samples (18 males, 24 females) had the G6PD Viangchan mutation (n = 42, 6.1%). Conclusions: G6PD Viangchan variant, which can cause severe haemolysis in the carrier when exposed to primaquine, was detected among 6.1% of the villagers in Champasak and 5.2% in Savannakhet but not in Phongsaly in this study. G6PD Viangchan variant might be common in the south of Laos but not so in the north. In the north, other G6PD deficiency variants might be more prevalent. However, in order not to overlook anyone and ensure a safe primaquine therapy for people living in malaria endemic areas in Lao PDR, G6PD testing is necessary.
Pathogens
Schistosomiasis mekongi infection represents a public health concern in Laos and Cambodia. While ... more Schistosomiasis mekongi infection represents a public health concern in Laos and Cambodia. While both countries have made significant progress in disease control over the past few decades, eradication has not yet been achieved. Recently, several studies reported the application of loop-mediated isothermal amplification (LAMP) for detecting Schistosoma DNA in low-transmission settings. The objective of this study was to develop a LAMP assay for Schistosoma mekongi using a simple DNA extraction method. In particular, we evaluated the utility of the LAMP assay for detecting S. mekongi DNA in human stool and snail samples in endemic areas in Laos. We then used the LAMP assay results to develop a risk map for monitoring schistosomiasis mekongi and preventing epidemics. A total of 272 stool samples were collected from villagers on Khon Island in the southern part of Laos in 2016. DNA for LAMP assays was extracted via the hot-alkaline method. Following the Kato-Katz method, we determined t...
<p>The socio-demographic data of the participants (N = 719).</p
<p>Flowchart summary of malaria screening based on the clinical and PCR data.</p
BMJ Open
ObjectivesThis mixed methods study was conducted to explore the barriers and facilitators for hea... more ObjectivesThis mixed methods study was conducted to explore the barriers and facilitators for health-seeking behaviours in a malaria endemic district in Lao PDR.DesignA convergent mixed methods design.SettingTwo malaria endemic villages in Thapangthong district, Savannakhet Province, Lao PDR.ParticipantsVillagers and healthcare workers in the two villages in Thapangthong district.MethodsIn the quantitative part, a pretested questionnaire was used to identify the health-seeking behaviours of the villagers. In the qualitative part, focus group discussions were employed to explore health-seeking behaviours of the villagers and in-depth interviews were used to explore the perceptions of the healthcare workers. Descriptive statistics were computed and multiple logistic regressions were used to identify the factors associated with perceived severity and perceived susceptibility. Thematic analysis was used to analyse the qualitative data. Quantitative and qualitative results were integrate...
<p>Multivariate logistic regression analyses to identify risk factors for <i>Plasmodi... more <p>Multivariate logistic regression analyses to identify risk factors for <i>Plasmodium</i> infections.</p
<p>The numbers of participants in the three districts of Attapeu province.</p
<p>The sensitivity and specificity of microscopy and the RDT in comparison to real-time PCR... more <p>The sensitivity and specificity of microscopy and the RDT in comparison to real-time PCR.</p
<p>Don Ngew and Hard Sun villages are located in Xaysetha district (API = 31.2); Vong Say a... more <p>Don Ngew and Hard Sun villages are located in Xaysetha district (API = 31.2); Vong Say and Ta Oum villages are located in Phouvong district (API = 103.4); and Hard Sai Soung and Som Poi villages are located in Sanamxay district (API = 59.9). API, annual parasite incidence (according to the API data from 2013). Map of Laos (left), Data source: CIESIN, CIAT, GPW, Available from: <a href="http://sedac.ciesin.columbia.edu/gpw" target="_blank">http://sedac.ciesin.columbia.edu/gpw</a>. Map of Attapeu province (right) was created by the authors.</p
Additional file 1: Appendix S1. Villagersâ information.
Additional file 9. Frequencies of the k13 mutations in the districts.
Additional file 8. PCR genotyping based on msp1 and msp2.
Additional file 7. Bivariate analyses to identify an association between variables and Plasmodium... more Additional file 7. Bivariate analyses to identify an association between variables and Plasmodium falciparum infections with the k13 mutations in the five provinces.
Additional file 6. Haplotypes based on the two flanking loci of the k13 gene in the six provinces... more Additional file 6. Haplotypes based on the two flanking loci of the k13 gene in the six provinces, summarized by frequency of the haplotypes.
Additional file 5. Haplotypes based on the two flanking loci of the k13 gene in the six provinces... more Additional file 5. Haplotypes based on the two flanking loci of the k13 gene in the six provinces, summarized by provinces.
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Papers by Phonepadith Khattignavong