Chea Nguon

Cambodia National Malaria Center

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Arjen M. Dondorp

Mahidol University

Rupam Tripura

Mahidol Oxford Tropical Medicine Research Unit

Thomas J. Peto

Mahidol Oxford Tropical Medicine Research Unit

Nicholas J. White

University of Oxford

Lorenz von Seidlein

Mahidol University

Nicholas Day

Mahidol University

Mallika Imwong

Mahidol Oxford Tropical Medicine Research Unit

Mehul Dhorda

Mahidol Oxford Tropical Medicine Research Unit

Phaik Yeong Cheah

University of Oxford

Duong Socheat

Ministry of Health

Cooperative Institutions

Mahidol University

130

Mahidol Oxford Tropical Medicine Research Unit

130

University of Oxford

125

Cambodia National Malaria Center

London School of Hygiene & Tropical Medicine

Institut Pasteur du Cambodge

Hospital for Tropical Diseases

Wellcome Sanger Institute

Centre for Human Genetics

Angkor Hospital for Children

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Focused Screening and Treatment (FSAT): A PCR-Based Strategy to Detect Malaria Parasite Carriers and Contain Drug Resistant P. falciparum, Pailin, Cambodia

PLoS ONE (2012)

Stefan Hoyer Sokomar Nguon Saorin Kim Najibullah Habib Nimol Khim

Recent studies have shown that Plasmodium falciparum malaria parasites in Pailin province, along the border between Thailand and Cambodia, have become resistant to artemisinin derivatives. To better define the epidemiology of P. falciparum populations and to assess the risk of the possible spread of these parasites outside Pailin, a new epidemiological tool named "Focused Screening and Treatment" (FSAT), based on active molecular detection of asymptomatic parasite carriers was introduced in 2010. Cross-sectional malariometric surveys using PCR were carried out in 20 out of 109 villages in Pailin province. Individuals detected as P. falciparum carriers were treated with atovaquone-proguanil combination plus a single dose of primaquine if the patient was non-G6PD deficient. Interviews were conducted to elicit history of cross-border travel that might contribute to the spread of artemisinin-resistant parasites. After directly observed treatment, patients were followed up and re-examined on day 7 and day 28. Among 6931 individuals screened, prevalence of P. falciparum carriers was less than 1%, of whom 96% were asymptomatic. Only 1.6% of the individuals had a travel history or plans to go outside Cambodia, with none of those tested being positive for P. falciparum. Retrospective analysis, using 2010 routine surveillance data, showed significant differences in the prevalence of asymptomatic carriers discovered by FSAT between villages classified as "high risk" and "low risk" based on malaria incidence data. All positive individuals treated and followed-up until day 28 were cured. No mutant-type allele related to atovaquone resistance was found. FSAT is a potentially useful tool to detect, treat and track clusters of asymptomatic carriers of P. falciparum along with providing valuable epidemiological information regarding cross-border movements of potential malaria parasite carriers and parasite gene flow.

Primaquine

Atovaquone

Asymptomatic carrier

Proguanil

10.1371/journal.pone.0045797

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Citations (72)

Post-implementation survey

Susanna Dunachie Pengby Ngor Lisa J. White Jeremy Chalk Yoel Lubell

This data shows the results of the survey of village malaria workers on their experiences of using smartphones with a novel software application for collecting data.

10.6084/m9.figshare.6327221.v1

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Citations (0)

Performance of “VIKIA Malaria Ag Pf/Pan” (IMACCESS®), a new malaria rapid diagnostic test for detection of symptomatic malaria infections

Malaria Journal (2012)

Monidarin Chou Saorin Kim Nimol Khim Sophy Chy Sarorn Sum

Abstract Background Recently, IMACCESS ® developed a new malaria test (VIKIA Malaria Ag Pf/Pan™), based on the detection of falciparum malaria (HRP-2) and non-falciparum malaria (aldolase). Methods The performance of this new malaria rapid diagnostic test (RDT) was assessed using 1,000 febrile patients seeking malaria treatment in four health centres in Cambodia from August to December 2011. The results of the VIKIA Malaria Ag Pf/Pan were compared with those obtained by microscopy, the CareStart Malaria™ RDT (AccessBio®) which is currently used in Cambodia, and real-time PCR (as “gold standard”). Results The best performances of the VIKIA Malaria Ag Pf/Pan™ test for detection of both Plasmodium falciparum and non- P. falciparum were with 20–30 min reading times (sensitivity of 93.4% for P. falciparum and 82.8% for non- P. falciparum and specificity of 98.6% for P. falciparum and 98.9% for non- P. falciparum ) and were similar to those for the CareStart Malaria™ test. Conclusions This new RDT performs similarly well as other commercially available tests (especially the CareStart Malaria™ test, used as comparator), and conforms to the World Health Organization’s recommendations for RDT performance. It is a good alternative tool for the diagnosis of malaria in endemic areas.

Rapid diagnostic test

Parasitology

Diagnosis of malaria

Gold standard (test)

Tropical Medicine

10.1186/1475-2875-11-295

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Citations (23)

VILLAGE MALARIA WORKER PERFORMANCE KEY TO THE ELIMINATION OF ARTEMISININ-RESISTANT MALARIA: A WESTERN CAMBODIA HEALTH SYSTEM ASSESSMENT

American Journal of Tropical Medicine and Hygiene (2017)

Sara E. Canavati Saranath Lawpoolsri Cesia E. Quintero Po Ly Chea Nguon

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ARE PLANTATIONS A HOTSPOT OF MALARIA TRANSMISSION IN CAMBODIA? AN ECOLOGICAL STUDY AND MATHEMATICAL MODEL

American Journal of Tropical Medicine and Hygiene (2017)

Simon C. Mendelsohn Anddouglas C. Pratt P Nou Laura Merson Chea Nguon

Hotspot (geology)

Disease Transmission

Source

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‘I could not join because I had to work for pay.’: A qualitative evaluation of falciparum malaria pro-active case detection in three rural Cambodian villages

PLoS ONE (2018)

Pierluigi Taffon Gabriele Rossi Jean-Marie Kindermans Rafaël Van den Bergh Chea Nguon

Background Pro-active case detection (Pro-ACD), in the form of voluntary screening and treatment (VSAT) following community mobilisation about 'asymptomatic malaria', is currently being evaluated as a tool for Plasmodium falciparum elimination in Preah Vihear Province, Cambodia. Methods A qualitative study was conducted to explore community understanding, perceptions, expectations and acceptability of the Pro-ACD intervention in order to identify aspects that could be improved in future Pro-ACD activities. This was ancillary to a three-round VSAT campaign, carried out in three villages between December 2015 and March 2016. Qualitative data collection began shortly after the end of the three rounds of screening. Purposive sampling was used to select participants. Nine focus group discussions with participants (n = 46) and non-participants (n = 40) in the Pro-ACD screening were conducted, in addition to in-depth interviews with key village figures (n = 9). Results Health promotion messages were well delivered and received, but it was difficult for many villagers to understand the messages around 'asymptomatic malaria'. Overall, villagers and village leaders had a positive opinion about the VSAT intervention. Acceptability was high, as a direct consequence of favourable perceptions towards the screening activity: the Pro-ACD intervention was seen by the local population as an effective, inexpensive, reliable and readily available tool to protect individuals and the community from the insurgence of malaria. Physical absence and lack of time (both linked to work-related activities) were the main reasons for non-participation. Conclusions Although VSAT was generally well perceived and accepted, the 'time factor' related to the need to satisfy essential daily subsistence requirements played a significant role in determining participation in the screening. More well-adapted and meaningful Pro-ACD approaches could be implemented by improving the timing of the testing activites, and strengthening community participation and engagement to increase acceptability.

Promotion (chess)

10.1371/journal.pone.0195809

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Citations (10)

Performance of the CareStart™ G6PD Deficiency Screening Test, a Point-of-Care Diagnostic for Primaquine Therapy Screening

PLoS ONE (2011)

Saorin Kim Chea Nguon Bertrand Guillard Duong Socheat Sophy Chy

Development of reliable, easy-to-use, rapid diagnostic tests (RDTs) to detect glucose-6-phosphate dehydrogenase (G6PD) deficiency at point of care is essential to deploying primaquine therapies as part of malaria elimination strategies. We assessed a kit under research and development called CareStart™ G6PD deficiency screening test (Access Bio, New Jersey, USA) by comparing its performance to quantitative G6PD enzyme activity using a standardized spectrophotometric method ('gold standard'). Blood samples (n = 903) were collected from Cambodian adults living in Pailin province, western Cambodia. G6PD enzyme activities ranged from 0 to 20.5 U/g Hb (median 12.0 U/g Hg). Based on a normal haemoglobin concentration and wild-type G6PD gene, the normal values of G6PD enzymatic activity for this population was 3.6 to 20.5 U/g Hg (95th percentiles from 5.5 to 17.2 U/g Hg). Ninety-seven subjects (10.7%) had <3.6 U/g Hg and were classified as G6PD deficient. Prevalence of deficiency was 15.0% (64/425) among men and 6.9% (33/478) among women. Genotype was analyzed in 66 G6PD-deficient subjects and 63 of these exhibited findings consistent with Viangchang genotype. The sensitivity and specificity of the CareStart™ G6PD deficiency screening test was 0.68 and 1.0, respectively. Its detection threshold was <2.7 U/g Hg, well within the range of moderate and severe enzyme deficiencies. Thirteen subjects (1.4%, 12 males and 1 female) with G6PD enzyme activities <2 U/g Hg were falsely classified as "normal" by RDT. This experimental RDT test here evaluated outside of the laboratory for the first time shows real promise, but safe application of it will require lower rates of falsely "normal" results.

Primaquine

Glucose-6-Phosphate Dehydrogenase Deficiency

Glucosephosphate Dehydrogenase Deficiency

Point of care

Point-of-Care Testing

Gold standard (test)

10.1371/journal.pone.0028357

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Citations (112)

Exploring the Contribution of Candidate Genes to Artemisinin Resistance in Plasmodium falciparum

Antimicrobial Agents and Chemotherapy (2010)

Mallika Imwong Arjen M. Dondorp François Nosten Poravuth Yi Mathirut Mungthin

The reduced in vivo sensitivity of Plasmodium falciparum has recently been confirmed in western Cambodia. Identifying molecular markers for artemisinin resistance is essential for monitoring the spread of the resistant phenotype and identifying the mechanisms of resistance. Four candidate genes, including the P. falciparum mdr1 (pfmdr1) gene, the P. falciparum ATPase6 (pfATPase6) gene, the 6-kb mitochondrial genome, and ubp-1, encoding a deubiquitinating enzyme, of artemisinin-resistant P. falciparum strains from western Cambodia were examined and compared to those of sensitive strains from northwestern Thailand, where the artemisinins are still very effective. The artemisinin-resistant phenotype did not correlate with pfmdr1 amplification or mutations (full-length sequencing), mutations in pfATPase6 (full-length sequencing) or the 6-kb mitochondrial genome (full-length sequencing), or ubp-1 mutations at positions 739 and 770. The P. falciparum CRT K76T mutation was present in all isolates from both study sites. The pfmdr1 copy numbers in western Cambodia were significantly lower in parasite samples obtained in 2007 than in those obtained in 2005, coinciding with a local change in drug policy replacing artesunate-mefloquine with dihydroartemisinin-piperaquine. Artemisinin resistance in western Cambodia is not linked to candidate genes, as was suggested by earlier studies.

10.1128/aac.00032-10

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Citations (122)

The feasibility and acceptability of mass drug administration for malaria in Cambodia: a mixed-methods study

Transactions of the Royal Society of Tropical Medicine and Hygiene (2018)

Thomas J. Peto Rupam Tripura Nou Sanann Bipin Adhikari James J. Callery

Abstract Background Mass drug administrations (MDAs) are part of the World Health Organization’s Plasmodium falciparum elimination strategy for the Greater Mekong Subregion (GMS). In Cambodia, a 2015–2017 clinical trial evaluated the effectiveness of MDA. This article explores factors that influence the feasibility and acceptability of MDA, including seasonal timing, financial incentives and the delivery model. Methods Quantitative data were collected through structured questionnaires from the heads of 163 households. Qualitative data were collected through 25 semi-structured interviews and 5 focus group discussions with villagers and local health staff. Calendars of village activities were created and meteorological and malaria treatment records were collected. Results MDA delivered house-to-house or at a central point, with or without compensation, were equally acceptable and did not affect coverage. People who knew about the rationale for the MDA, asymptomatic infections and transmission were more likely to participate. In western Cambodia, MDA delivered house-to-house by volunteers at the end of the dry season may be most practicable but requires the subsequent treatment of in-migrants to prevent reintroduction of infections. Conclusions For MDA targeted at individual villages or village clusters it is important to understand local preferences for community mobilisation, delivery and timing, as several models of MDA are feasible.

Mass drug administration

10.1093/trstmh/try053

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Citations (26)

Mass anti-malarial administration in western Cambodia: a qualitative study of factors affecting coverage

Malaria Journal (2017)

Christopher Pell Rupam Tripura Chea Nguon Phaikyeong Cheah Chan Davoeung

Mass anti-malarial administration has been proposed as a key component of the Plasmodium falciparum malaria elimination strategy in the Greater Mekong sub-Region. Its effectiveness depends on high levels of coverage in the target population. This article explores the factors that influenced mass anti-malarial administration coverage within a clinical trial in Battambang Province, western Cambodia. Qualitative data were collected through semi-structured interviews and focus group discussions with villagers, in-depth interviews with study staff, trial drop-outs and refusers, and observations in the communities. Interviews were audio-recorded, transcribed and translated from Khmer to English for qualitative content analysis using QSR NVivo. Malaria was an important health concern and villagers reported a demand for malaria treatment. This was in spite of a fall in incidence over the previous decade and a lack of familiarity with asymptomatic malaria. Participants generally understood the overall study aim and were familiar with study activities. Comprehension of the study rationale was however limited. After the first mass anti-malarial administration, seasonal health complaints that participants attributed to the anti-malarial as "side effects" contributed to a decrease of coverage in round two. Staff therefore adapted the community engagement approach, bringing to prominence local leaders in village meetings. This contributed to a subsequent increase in coverage. Future mass anti-malarial administration must consider seasonal disease patterns and the importance of local leaders taking prominent roles in community engagement. Further research is needed to investigate coverage in scenarios that more closely resemble implementation i.e. without participation incentives, blood sampling and free healthcare.

Mass drug administration

Qualitative property

10.1186/s12936-017-1854-4

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Citations (51)