Evaluation of community-based systems for the surveillance of day three-positive Plasmodium falciparum cases in Western Cambodia.

BACKGROUND: Delayed clearance of Plasmodium falciparum parasites is used as an operational indicator of potential artemisinin resistance. Effective community-based systems to detect P. falciparum cases remaining positive 72 hours after initiating treatment would be valuable for guiding case follow-up in areas of known resistance risk and for detecting areas of emerging resistance. METHODS: Systems incorporating existing networks of village malaria workers (VMWs) to monitor day three-positive P. falciparum cases were piloted in three provinces in western Cambodia. Quantitative and qualitative data were used to evaluate the wider feasibility and sustainability of community-based surveillance of day three-positive P. falciparum cases. RESULTS: Of 294 day-3 blood slides obtained across all sites (from 297 day-0 positives), 63 were positive for P. falciparum, an overall day-3 positivity rate of 21%. There were significant variations in the systems implemented by different partners. Full engagement of VMWs and health centre staff is critical. VMWs are responsible for a range of individual tasks including preparing blood slides on day-0, completing forms, administering directly observed therapy (DOT) on days 0-2, obtaining follow-up slides on day-3 and transporting slides and paperwork to their supervising health centre. When suitably motivated, unsalaried VMWs are willing and able to produce good quality blood smears and achieve very high rates of DOT and day-3 follow-up. CONCLUSIONS: Community-based surveillance of day-3 P. falciparum cases is feasible, but highly intensive, and as such needs strong and continuous support, particularly supervision and training. The purpose and role of community-based day-3 surveillance should be assessed in the light of resource requirements; scaling-up would need to be systematic and targeted, based on clearly defined epidemiological criteria. To be truly comprehensive, the system would need to be extended beyond VMWs to other public and private health providers

Novel approaches to risk stratification to support malaria elimination: an example from Cambodia.

BACKGROUND: Accurate malaria stratification is essential for effective targeting of interventions but represents a particular challenge in pre-elimination settings. In these settings transmission is typically sufficiently low and spatially heterogeneous to warrant a need for estimates of malaria risk at sub-district or village level but is also likely to be sufficiently high to render the type of decision support systems appropriate to the final stages of malaria elimination impractical. In such a scenario it is arguably more feasible to strengthen existing passive malaria surveillance systems so that routinely generated case data can provide an effective basis for stratifying malaria risk. This paper explores the utility of routine malaria surveillance data for the stratification of malaria risk in Cambodia, where the target is malaria elimination by 2025. METHODS: A malaria information system (MIS) was developed to generate timely, routine data on temporal and spatial variations in malaria cases reported through public health facilities and village malaria workers (VMWs). The MIS was implemented across all malaria endemic districts in the country during 2010-11. In 2012 MIS data were extracted and assessed on the basis of coverage and completeness. Village-level incidence estimates for 2011 were generated using predefined data inclusion criteria. RESULTS: In 2011, the MIS covered 681 health facilities and 1,489 VMW villages; the overall completeness of monthly reporting was 82& and 97& for health facilities and VMWs respectively. Using these data it was possible to estimate malaria incidence for 89& of villages covered by the MIS. The resulting stratification highlights the highly heterogeneous nature of malaria transmission in Cambodia and underlines the importance of village-level data for effective targeting of interventions, including VMWs. Challenges associated with implementing the MIS and the implications of these for developing viable and sustainable MIS in Cambodia and elsewhere are discussed. CONCLUSIONS: This study demonstrates the operational feasibility of introducing a system to routinely generate village level malaria case data in Cambodia. Although resulting incidence estimates are subject to various limitations and biases the data provide an objective, repeatable basis for a dynamic system of stratification which is appropriate for guiding the transition between malaria pre-elimination and elimination phases

Prevalence of K13 mutation and Day-3 positive parasitaemia in artemisinin-resistant malaria endemic area of Cambodia: a cross-sectional study

Abstract Background The presence of artemisinin-resistant malaria parasites was confirmed in western Cambodia in 2009. In 2013, mutations in the propeller domain of the kelch protein K13 was found to be associated with artemisinin resistance. A cross-sectional study was conducted to determine the prevalence of Day-3 parasitaemia, estimate the frequency of k13 molecular marker and assess their relationship in the context of operational research. Methods Blood smears and filter paper blood spots were collected from febrile patients in Kravanh District, Pursat Province. The blood smears were examined by microscopy, and blood spots by a k13 mutation assay. Results Data from 92 patients were analysed. Only one was positive for Day-3 parasitaemia. Results of the k13 assay were interpretable for 76 of the 92 samples. The findings were: wild type: 9 (12%), C580Y: 64 (84%), Y493H: 3 (4%). Therefore, despite the high prevalence of k13 mutants (67/76: 88%), only 1 of the 92 patients remained blood smear positive for Plasmodium falciparum on Day-3. Conclusions These preliminary findings suggest good potency of artemisinin despite the dominance of k13 mutation in Kravanh, but the result is not necessarily representative of the western part of Cambodia. Further investigation should be made to determine if k13 marker remains useful as a tool for tracking artemisinin resistance and predicting the trend of the efficacy of artemisinin combination therapy once the mutant alleles have been well established in the population

Correction to: Prevalence of K13 mutation and Day-3 positive parasitaemia in artemisinin-resistant malaria endemic area of Cambodia: a cross-sectional study

After publication of the article [1], it has been brought to our attention that the funding acknowledgements for this article are incomplete. The authors would like to also include the following