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Table 2 Example of the cyclical work process of the Vivax Working Group (surveillance theme)

From: Targeting vivax malaria in the Asia Pacific: The Asia Pacific Malaria Elimination Network Vivax Working Group

Identify knowledge gaps

In the first round of the Country Partner Technical Development Programme (CPTDP) undertaken in 2011, 5 of the 11 successful grant recipients proposed P. vivax genotyping studies. These studies were funded in China, Indonesia, Malaysia, South Korea and Sri Lanka. It was apparent that several of the partners shared similar objectives and challenges in the design and interpretation of the proposed studies. The VxWG identified the need for new strategies to monitor the impact of interventions on the local parasite population, identify local hotspots of transmission, and detect rapidly emerging/outbreak strains (identified as the rapid expansion of infections with identical genotypes) early. In addition, several partners highlighted the need for molecular tools to confirm imported cases and determine their geographic origin; this cannot be addressed without an integrated, multi-country approach. The VxWG coordinating team therefore held a workshop to facilitate standardized methodologies.

Build consensus

In 2011, a P. vivax genotyping workshop was held in Sabah, Malaysia, to identify the markers that would best address the partners’ needs. A consensus panel of 9 short tandem repeat markers (STR) were selected to aid characterization of P. vivax within-host and population diversity as this reflects parasite transmission patterns. It was agreed that more information on the genome-wide diversity of parasites from different countries would be needed to identify optimal geographic markers. Nonetheless, the data generated on the tandem repeat markers would aid a feasibility analysis of the ability to distinguish infections from different countries using molecular methods. In 2012, a second P. vivax genotyping workshop was convened in Incheon, South Korea, to discuss approaches to facilitate data analysis and data sharing between the country partners. The partners agreed to a custom-made web-based platform (http://www.vivaxgen.menzies.edu.au) to facilitate these processes.

Gather the evidence

To date three of the CPTDP studies have been published. In the low endemic settings of Sabah, Malaysia, P. vivax genotyping demonstrated large clusters of identical strains emerging in the population [38]. This finding emphasized the critical need for parasite molecular surveillance to identify rapidly emerging strains (infections with identical genotype profiles at the 9 STRs) which might reflect highly adaptive strains such as drug resistant strains before they spread extensively: conventional surveillance methods do not address this challenge. In Central China, using samples collected in 2007–2010, low differentiation (frequent gene flow) was observed between parasite populations from Anhui Province, where P. vivax remains endemic, and neighbouring Jiangsu Province, where no local cases have been detected since 2012 [24]. This finding highlighted the risks of resurgence in highly mobile human populations. In Indonesia, genotyping demonstrated higher diversity lower differentiation in P. vivax versus P. falciparum [12], possibly reflecting greater potential for spread in P. vivax. The same trend was observed in the Solomon Islands in a study led by researchers at the Australian Army Malaria Institute (an APMEN Partner Institute) [10]. This finding further emphasized the adaptive potential of P. vivax and the need to maintain diligent surveillance in pre-elimination settings.

Change practice

Studies using the consensus markers are currently underway in a further nine countries, including 3 remaining CPTDP studies in Bhutan, South Korea and Sri Lanka.