My field experience in fighting malaria in Africa started with five years in central Sudan where I helped organize the Blue Nile Health Project in 1979, aimed at protecting 2 million people in the million acre Gezira Irrigation System. I benefited a great deal from the malaria experience of my Sudanese colleagues, as well as from the Iranians and others in the WHO Regional Office for the Eastern Mediterranean. I also benefited from the support of WHO Geneva, and from Letitia Obeng in UNEP.
With the benefit of their experience, we developed the Kitchen Sink Strategy against malaria and other water-associated diseases. We realized the importance of using every available method in an integrated strategy - except the proverbial Kitchen Sink of course. This included careful management of water resources including improvements in existing irrigation and drainage systems, organization of community action groups in each village to improve health awareness and surface drainage, and increased diagnostic and treatment capabilities for the entire project area.
The 150 million dollar project was highly successful for ten years. But when the funding ended and a devastating military coup crippled our drainage program, malaria returned with a vengeance. At first I thought that this disaster was the fate of all short malaria control efforts in Africa – ‘The Immunity Trap’. We ran into this trap because we had held the malaria prevalence below 1% during the ten years of the project. So in 1989 when the project ended, most children under 10 years of age had never been exposed to malaria, and had developed no immunity. The rest of the population had also lost much of their immunity. The return of malaria was thus devastating to the whole population.
But to my surprise, that was only part of the story. The other part which I realized only recently, had been the impact of drought. If you recall the horrible Ethiopian famine of 1985, it was caused by a regional drought which had started a few years earlier and gradually depleted the water and food reserves of the upper Nile River Valley around Ethiopia and Sudan. The drought broke in 1989, the same year our project ended.
We had not realized that the unusually effective suppression of malaria during the ten years of our project had been amplified by the absence of rainfall along the Blue Nile River during the same period. And the lethal return of malaria in 1990 - when prevalences in school children rose above 30% and cerebral malaria killed and maimed thousands - was due not only to the Immunity Trap, but also to the heavy rains which washed over Ethiopia and Sudan, and the consequent increase in mosquitoes and malaria transmission.
This was an important lesson to me about the importance of rainfall in the epidemiology and control of malaria. Droughts might help suppress malaria, and heavy rains after the drought could exacerbate the lethal impact of malaria’s return.
I thus recommend to the folks who run the US Presidential Malaria Initiative, and to all malaria people in the Roll Back Malaria Program and WHO, that you be zealous about collecting data on rainfall, mosquitoes and malaria before and during your programs, and that you continue to be aware of the extra potential for the Immunity Trap in drought-prone areas. To avoid the Immunity Trap, you must develop an integrated strategy which includes permanent measures - such as drainage, screened houses and community action programs - to supplement the ephemeral methods based on drugs and biocides. Otherwise you are putting large populations at risk from a lethal outbreak when your program ends, or when heavy rains end the drought. So beware the Immunity Trap. Also watch out for military dictators. Dictators are as bad as mosquitoes.