It is valuable and refreshing to see contributions to strategies for malaria suppression in Africa from other disciplines, such as economics. Killeen and Reed pointed out that the portfolio effect cushions mosquito populations and malaria transmission against vector control interventions.(Killeen GF, Reed TE. Malar J. 2018 Aug 10;17(1):291. doi: 10.1186/s12936-018-2441-z.) Thus it must be considered when planning a strategy for Africa.
*** In developing the comprehensive program of the Blue Nile Health Project in Sudan in 1979 against malaria and other water-associated diseases, we followed the Kitchen Sink Strategy, in which we employed every possible method together, except for the proverbial Kitchen Sink. It was an indirect acceptance of the portfolio effect. Thus the multiple elements of the strategy overlapped, giving a robust attack on malaria transmission, as well as attacking other water-associated diseases.
(The Blue Nile Health Project: a comprehensive approach to the prevention and control of water-associated diseases in irrigated schemes of the Sudan. AA el Gaddal - The Journal of tropical medicine and hygiene, 1985 - ncbi.nlm.nih.gov) We agree with Killeen and Reed that the portfolio effect cushions mosquito populations and malaria transmission against vector control interventions, and must be recoginized in planning global strategies.***
Thus a strategy with a diversified portfolio is the logical way to attack such a multi-faceted disease as malaria in Africa.
In addition to the conventional use of drugs and biocides, the highly successful Blue Nile strategy which protected over a million people from malaria for 10 years, included improved irrigation and drainage techniques, sophisticated water management, permanent ellmination of mosquito breeding sites by filling or drainage, housing improvements with metallic screens, health education and biological control.
In contrast, the narrow focus of the current WHO and US PMI strategies based solely on drugs, biocides and bednets, is bound to result in expensive failures. This is partly because they ignore the resistance treadmill, but also the portfolio effect, something new to learn.
William Jobin Director of Blue Nile Associates