Characterisation of Plasmodium vivax lactate dehydrogenase dynamics in P. vivax infections

Plasmodium vivax lactate dehydrogenase (PvLDH) is an essential enzyme in the glycolytic pathway of P. vivax. It is widely used as a diagnostic biomarker and a measure of total-body parasite biomass in vivax malaria. However, the dynamics of PvLDH remains poorly understood. Here, we developed mathematical models that capture parasite and matrix PvLDH dynamics in ex vivo culture and the human host. We estimated key biological parameters characterising in vivo PvLDH dynamics based on longitudinal data of parasitemia and PvLDH concentration collected from P. vivax-infected humans, with the estimates informed by the ex vivo data as prior knowledge in a Bayesian hierarchical framework. We found that the in vivo accumulation rate of intraerythrocytic PvLDH peaks at 10-20 h post-invasion (late ring stage) with a median estimate of intraerythrocytic PvLDH mass at the end of the life cycle to be 9.4 × 10-3ng. We also found that the median estimate of in vivo PvLDH half-life was approximately 21.9 h. Our findings provide a foundation with which to advance our quantitative understanding of P. vivax biology and will facilitate the improvement of PvLDH-based diagnostic tools.

Perspectives of health and community stakeholders on community-delivered models of malaria elimination in Lao People’s Democratic Republic: A qualitative study

In the Lao People’s Democratic Republic (Lao PDR), village health volunteers play an important role in providing health services including those to reduce the burden of malaria. Over the last two decades, the volunteer network has expanded to bring malaria services closer to communities and contributed to the reduction of malaria cases. However, as malaria test positivity rates decreased, many volunteers have lost motivation to continue providing routine malaria services, and other services they provide may not reflect growing healthcare demands for common diseases in the community. This study explored the perspectives, knowledge and inputs of key health stakeholders and community members in southern Lao PDR on community-delivered models in order to refine the volunteer model in the context of Lao PDR’s primary health care sector and malaria elimination goals. Semi-structured interviews with multi-level health stakeholders, participatory workshops with community leaders, and focus group discussions with community members and current village health volunteers were conducted. Deductive followed by inductive thematic analysis was used to explore and categorise stakeholders’ perspectives on community-delivered models for malaria elimination. Both stakeholders and community members agreed that village health volunteers are essential providers of malaria services in rural communities. Apart from malaria, community members identified dengue, diarrhoea, influenza, skin infections and tuberculosis as priorities (in descending order of importance) and requested community-based primary health care for these diseases. Stakeholders and community members suggested integrating prevention, diagnosis, and treatment services for the five priority diseases into the current malaria volunteer model. A divergence was identified between community members’ expectations of health services and the services currently provided by village health volunteers. Stakeholders proposed an integrated model of healthcare to meet the needs of the community and help to maintain volunteers’ motivation and the long-term sustainability of the role. An evidence-based, integrated community-delivered model of healthcare should be developed to balance the needs of both community members and stakeholders, with consideration of available resources and current health policies in Lao PDR.