Malaria

Malaria, caused by the Plasmodium parasite, is a major cause of childhood mortality in low and middle-income countries, resulting in an estimated 660,000 deaths in 2012, with the majority occurring in children under the age of 5 in sub-Saharan Africa.

Current challenges in Malaria research

  • Over the past decade, increased funding for malaria has led to the more widespread availability of both preventive interventions (such as long-lasting insecticide treated nets) and appropriate treatment. This has resulted in an estimated 42% decline in deaths since 2000.
  • Whilst severe forms of malaria require hospitalisation, these can be prevented if treated promptly with an appropriate antimalarial drug. Diagnostics are an essential part of clinical care, with recently developed rapid diagnostic tests allowing both clinical staff and community health workers to identify and treat malaria cases.
  • Whilst progress has been rapid, challenges remain. Transmission remains intense in many parts of the world and resistance to both the insecticides and drugs is emerging. New tools and strategies will be needed to continue to drive down transmission and ultimately to eradicate the parasite.

Why diagnostics are essential in malaria control & elimination strategies

  • Current rapid diagnostic tests were developed to identify and hence appropriately treat symptomatic disease. However, a large proportion of individuals carry the parasite without exhibiting symptoms. Diagnostics are needed to detect and treat these “silent carriers” if we are to further reduce transmission.
  • Mass screen and treat (MSAT) and targeted Mass Drug Administration (MDA) strategies are being considered in addition to ongoing vector control programmes to interrupt transmission of Plasmodium falciparum malaria by clearing the human infectious reservoir. The Diagnostics Modelling Consortium exercise will seek to identify the product profile for a field-based diagnostic that is best suited to such scenarios.

Project methodology

The exercise is based on three existing malaria transmission models and is utilising new data emerging on infectivity studies and diagnostic developments to address key issues including:

  • The profile of the human infectious reservoir and how this varies by epidemiological setting;
  • The relationships between parasite prevalence/density, gametocyte prevalence/density and transmissibility;
  • The distribution of the duration of infection in semi-immune populations and how this changes as immunity decays;
  • The level of diagnostic sensitivity that is required for MSAT and targeted MDA strategies to be successful in different transmission settings and at different stages of an elimination programme.

Key Research Questions

The primary research question aims to address "What product profile for a field-based malaria diagnostic is needed to ensure the success of MSAT strategies to reduce and interrupt transmission?"

Other secondary questions include:

  • How sensitive would a nucleic diagnostic test need to be?
  • How does this compare to an HRP-2 based diagnostic? How does the product profile vary by transmission setting?
  • What impact does varying detectability over the course of an infection have on the outcomes?

 

Key people: 
Prof Azra Ghani
Alison Reynolds
Lindsey Wu
Dr Patrick Walker
Dr Hannah Slater
Dr Steve Kern
Prof Chris Drakeley
Prof Thomas Smith
Dr Teun Bousema
Dr Amanda Ross
Dr Lisa White
Dr Yoel Lubell
Dr Bruno Moonen
Dr Thomas Kanyok
Dr Sophie Allauzen