115 Years of Malaria in Africa
UKZN’s College of Health Sciences Research Professor, Benn Sartorius was the second author, lead analyst and key member of the team that published an article in Nature documenting spatial-temporal trends for malaria in sub-Saharan Africa over a 115-year period.
The article, titled: The Prevalence of Plasmodium falciparum in sub Saharan Africa since 1900, was led by Professor Robert Snow (KEMRI-Wellcome Trust), a leading international malaria researcher. KEMRI-Wellcome Trust Researchers unveiled the largest repository of malaria survey data in Africa, covering over 50 000 surveys dating back to 1900, each documented by date, geolocation, number of people, and the proportion positive for Plasmodium falciparum infection.
This is the largest repository of any parasitic disease in the world. ‘Previous efforts to model the changing patterns of P. falciparum transmission intensity in Africa have been limited to more recent data points or have used maps drawn from historical expert opinions,’ explained the team.
The researchers analysed this data to estimate malaria infection prevalence for each of 520 administrative units of sub-Saharan African Countries and Madagascar for 16 time periods since 1900 through to 2010-2015.
The findings suggests that the African continent has witnessed a long-term decline in the prevalence of Plasmodium falciparum from 40% in the period 1900–1929 to 24% in the period 2010–2015, a trend that has been interrupted by periods of rapidly increasing or decreasing transmission. The findings would suggest that global initiatives have had minor impacts on malaria transmission, and a historically unprecedented decline has been observed since 2000.
Snow says ‘People often focus on recent history in tracking malaria in Africa, to inform donors and control programmes on recent actions. The longer history of malaria in Africa allows us to put into context the recent decline.’
‘The cycles and trend over the past 115 years are inconsistent with explanations in terms of climate or deliberate intervention alone,’ suggested Dr Noor.
‘The size and breadth of the data compiled by the team at KEMRI is invaluable’, explained Sartorius, ‘and allows unique insights into the spatial-temporal dynamics of malaria on the continent since the turn of the last century as well as assess short and long term trends in relation to historical and current climate conditions alongside control activities.’
Caution is required in projecting a future for malaria in Africa. ‘Inferring from these data to future trends, we would expect continued reductions in malaria transmission, punctuated with resurgences. The current prevalence of infection, 24%, is at its lowest in 115 years but gains have stalled since 2010 and 240 million infected individuals remains a substantial burden. Little has changed in the high transmission belt across west and central Africa. We are threatened by emerging insecticide and drug resistance and growing international ambivalence to funding control,’ said the team.
‘The history of malaria risk in Africa is complex, there have been perfect lulls when drugs worked and droughts prevented mosquito’s transmission infection; there have been perfect storms when drugs stopped working and flooding affected large parts of Africa. It has been a history of long term cycles and predicting the future of malaria in Africa based on climate or intervention coverage alone is difficult,’ says Snow.
‘We need new tools for the poor and high malaria burden areas of Africa. Focus on eliminating malaria in the low burden margins of southern Africa, or small islands across the world, runs the risk that high burden countries in Africa get ignored and left behind. The 115-year history shows that malaria in Africa is complex and predicting the future malaria based on climate or economic development alone would be foolhardy,’ continues Snow.
The team comprised of researchers from: Kenya Medical Research Institute-Wellcome Trust Collaborative Programme, Nairobi, Kenya and Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK and Public Health Medicine, School of Nursing and Public Health, University of KwaZulu-Natal, Durban, South Africa.
Words: Nombuso Dlamini