A team led by Dr Abdisalan Noor and Professor Robert Snow of the KEMRI-Wellcome Trust Research Programme produced the maps by geocoding data from surveys in 44 African countries and territories endemic for malaria in order to identify which populations were at risk of the disease in 2000 and 2010.
The time period coincides with the launch of the Roll Back Malaria Partnership, which brought with it a large increase in investment targeting malaria control, and the team aimed to investigate the progress in reducing transmission during this period. Their maps revealed that the number of people living in high-risk areas, where more than 50 per cent of the population are likely to carry infections, fell from 219 million in 2000 to 184 million in 2010, a fall of 16 per cent.
However, the maps also identified that just ten countries harbour 87 per cent of the population remaining at high-risk of disease transmission and intensity remained high or unchanged in eight countries including the Democratic Republic of Congo, Uganda, Malawi and South Sudan.
To ensure accuracy, the study used measurements for the prevalence of malaria in populations where diagnosis had been confirmed through laboratory techniques.
“Health information systems in many African countries are weak and it has been difficult to reliably estimate how many people get sick, or die, of malaria” said Dr Abdisalan Noor, who led the study. “The population surveys we used in this study are a more reliable indicator for tracking and we hope our study will help countries assess their progress and adapt their strategies for more effective malaria control.”
The study is one of the largest examples of mapping and modelling for any parasitic disease in Africa and is the first study to look at the changing intensity of malaria transmission across the African continent in order to assess the impact from the first ten years of the Roll Back Malaria Partnership.
Professor Robert Snow, who co-authored the study, said: “The results of our analysis are pause for thought. On the one hand it’s a glass half full, with several countries showing significant reductions in malaria transmission, and on the other it’s a glass half empty, where, despite a decade of massive investment in malaria control the populations living in several African countries are as likely to be infected with malaria in 2000 as they were 10 years later.”
Dr Noor added: “Advanced skills in spatial statistics and computing are enabling us to measure changes in malaria transmission in new ways and where they are most needed. By continuing to bring together dedicated scientists in Africa we can have better monitoring and tailor control of malaria transmission in the future.”
Despite the reductions seen the paper highlights the need for global support to sustain and further accelerate a decrease in malaria transmission.
The project was a pan-African effort using data provided by national malaria control programmes, researchers in sub-Saharan Africa and national and international archives.
Image: Anopheles gambiae. Credit: A Stich, Liverpool School of Tropical Medicine/Wellcome Images