Last Updated: 19/10/2014
Molecular tools for monitoring the impact of intensified malaria control on malaria epidemiology
Objectives
The objectives of this project are two-fold:
- To quantify the impact of intensified interventions by using novel molecular parameters.
- To investigate whether the biological differences between the four sympatric Plasmodium species renders them differentially susceptible to control measures.
This research will address key gaps in our knowledge and will provide tools for monitoring the effects of control measures on malaria epidemiology.
Swiss Tropical and Public Health Institute (Swiss TPH), Switzerland
The recent paradigm shift from malaria control to malaria elimination has led to renewed interest in field-based malaria research. As a result of roll out of intensified control by combined and sustained interventions, malaria transmission is expected to change. However, effects on transmission are difficult to quantify. The only Plasmodium stages transmittable to mosquitoes are gametocytes, but gametocytemia has been largely underestimated previously by light microscopy. Molecular typing of genes expressed only in gametocytes can provide more precise estimates.
In Papua New Guinea (PNG) all four human Plasmodium species prevail. Malaria control aiming at elimination is likely to cause changes in the relationship between the sympatric Plasmodium species. Interactions among multi-clonal co-infections of any species can be monitored over time in a longitudinal cohort. Survival of individual infections is tracked by genotyping each parasite clone using highly polymorphic markers. This permits a precise estimation of the force of infection despite concurrent ongoing infections, thus providing a novel molecular parameter. Here we propose a research agenda paralleling these upcoming control programs and public health activities in PNG.
Expected outcomes: (i) Basic knowledge on the differential effects of intensified malaria control on the incidence, complexity and dynamics of infection of P. falciparum and P. vivax. (ii) Basic knowledge on the epidemiology of transmission stages and transmission biology of multiple species and multiple-clone Plasmodium co-infections. (iii) Novel tools and molecular parameters will be made available for monitoring differential effects of control interventions on sympatric Plasmodium species.
The research team will use archived samples from field surveys conducted in 2009-2010 (i.e. before start of up-scaled massive anti-malarial interventions in late 2010) and from comparable studies conducted in 2012/13 (i.e. 2 years after start of anti-malarial interventions). The novelty compared to previous field studies consists of dedicated sampling procedures permitting RNA extractions. They will design and evaluate precise and robust tools for investigating density and diversity of gametocytes of three Plasmodium species in the study area by quantitative reverse transcription PCR or by capillary electrophoresis based genotyping of size polymorphic genes expressed in sexual stages. In addition, they will genotype all blood stage infections in cohort samples.
Apr 2011 — Apr 2015
$409,022
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