Bob Snow: The future of malaria in Africa
Although the map of malaria in Africa has seen little reduction since 1970, the likelihood of getting infected has never been so low. For further progress, we need better tools – insecticides, drugs and vaccines – as well as economic development and investments in health systems. Cartography of the disease helps design interventions, and a better understanding of how immunity develops will also shape the future of malaria in Africa.
My name is Professor Bob Snow, I work at the Kenya Medical Research Institute Wellcome Trust Programme and I am a malaria epidemiologist.
To briefly describe the history of malaria over the past 100 years would require more than 5 minutes, but in essence what has happened is that at the turn of the last century (around 1900), malaria probably reached its natural extent in Africa, including all of North Africa, all the offshore islands, and quite a long way south in Southern Africa. In the first 50-60 years, fantastic progress was made: malaria was eliminated from all of North Africa, there was no malaria in Réunion and Mauritius. Control efforts had actually shrunk the map of malaria in Africa, down to a section running from below the Sahara all the way across and down to South Africa. South Africa had also made progress, it shrunk its map of malaria further and further east to a constrained area around KwaZulu-Natal and Mpumalanga. Largely however, there was still a huge number of people still living under intense malaria transmission, from about 1970 until today, and the map hasn’t really shrunk very much since.
There has been a big reduction in the likelihood of being bitten by a mosquito infected with malaria. The number of people who have malaria in their blood has also dropped dramatically, but it has happened in waves. The first wave was when we introduced DDT and chloroquine in the 1940s, after the second world war. There was a big drop then and it remained quite low for a long time, until we had the perfect storm. There was El Niño epidemics in the 90s, increased rainfall, flooding and emerging resistance to chloroquine, then we had a massive peak, a huge epidemic across the whole continent. This caused the world to realise that we had to do something, with big efforts made to raise more money, global fund support, rollback malaria initiative. We introduced two other magic bullets: insecticide treated bednets, and artemisinin-based combination therapy. Malaria then began to drop, and we are at a stage now where it is much lower, the lowest it has ever been for over 100 years. It has however probably stagnated, so what we see today is a sort of bubbling along at a lower level, but still there and still affecting millions of people across Africa.
Africa is home to 98% of all the malaria burden worldwide: over 90% of all malarial deaths that occur in the entire world occur in Africa. There has been a lot of talk about eliminating malaria from the planet, several people have said that in their lifetimes, they don’t want to see malaria any more on the globe. But to be fair, Africa still has nearly 800 million people living in a belt across Africa where malaria is part of their daily lives. Half of them (400 million people) live in areas where 1 in 4 children walk around with malaria in their blood, today. The cradle of the world’s problem is still in Africa. You can’t ignore Africa. Africa has other issues, other problems which lead us to the current situation where there is still a lot of malaria, including poverty, poor governance, conflict, and lack of economic investment, which is why there needs to be a focus on Africa.
I think that we are doing everything that we can currently with the tools that we have available, but if I had to look to the future, we need more tools. One thing that we can learn from the history of malaria, is that the malaria parasite and the malaria mosquitoes are incredibly clever and very adaptable, and we are seeing resistance emerge to both drugs and insecticides. We need more effective insecticides, more effective drugs to combat what will happen in the future, which is an emerging resistance to both. We need vaccines. The vaccines that we currently have and are currently trying are okay, but they may not go to scale, they may not be good enough to implement at a wide population level, so we need continued investment in vaccines.
Two things make the biggest difference, and this is from history outside of Africa. The first is economic development: when you reach a point where all females go to school, there is electricity, there are paved roads, malaria does disappear. That is the one message that we need to fully understand, that the future of malaria in Africa depends largely on how well Africa develops economically as a continent. Allied to that is how well the health system is invested in. Governments across the continent need to invest in a strong health system. I don’t believe that malaria will be eliminated from Africa in my lifetime, nor anyone else’s lifetime, but there should be no deaths from malaria – that is unacceptable. Children should be treated quickly, they should get access to emergency care in hospitals when they need it, and no one should die. If I was to think of a future, and a future milestone, it would be that no child, no individual in Africa die of malaria, and I think that is achievable.
Our group here has been investing in mapping the risk of malaria in Kenya to begin with, then across Africa, and globally. That work has really transformed the way we think about disease, the way we think about investing in interventions. We work very closely with national governments and the World Health Organisation to try and identify areas where we might get the biggest bang for your buck, and areas where maybe giving everyone bednets is a waste of money. Using the cartography, the geography of malaria to design control, design investment has been one of our biggest achievements, and that is a space that will continue to grow.
The other area of work which I am now largely funded to do is the relationship between how often you get bitten by a mosquito carrying parasites and your speed of developing immunity. To this day, despite 100 years or so of research, we do not properly understand the relationship between infection and disease outcome. How likely are you to develop severe disease, given how often you are bitten by an infected mosquito, and how likely are you to die? This is a whole concept, a whole body of research that has been neglected for a very long period of time. To design what the future of malaria looks like, we need to understand that as well.
Malaria is still a major killer, you can’t neglect it from a research points of view. There was a massive increase announced just last week in donor assistance to malaria; the UK government for example has increased its budget to the global fund. It recognises, and the world recognises how important it is to get on top of malaria. There has been a shift, for which I am very grateful, to make sure a lot more of that investment goes into Africa for disease prevention and disease control. We need new tools and a better understanding of malaria. I cannot imagine why you would not increase the amount of money going into malaria research, if you increase the amount spent on its control, knowing that will only last for a short period of time.
Since about 2009, we have worked very closely with the Kenyan government to try and help it identify areas where you can increase the amount of intervention coverage, and areas where you might do things differently. We have shaped the Kenyan policy in that sense, beginning with work in 2009 by Dr Abdisalan Mohamed Noor, and that was very influential. We have extended that beyond Kenya’s borders: we work now in Somalia, Sudan, Djibouti, Tanzania, Uganda and many other countries where we provide government support for epidemiological intelligence, trying to understand the landscape of malaria in a country, so that they can design their national strategies effectively, they can invest in a clever way, using the science of malaria cartography, and understanding the epidemiology of the disease to shape that. That has been driven by us, here in Kenya. It has now grown into an initiative called the High burden to high impact initiative run by the WHO, but it began here, in the programme.
This interview was recorded in June 2019