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Malaria: Progress in the Face of History
Aug 26 2013 12:52PM Posted by David Ludwig, Ph.D.
 


Silent Spring. Touchstone of environmental management, wake-up call for millions. The focus of Silent Spring was on the broadcast spraying of DDT for pest insect control. Subsequently, the technical literature documented the food-web accumulation of DDT from the days of widespread application, and the decline in such concentrations after cessation.

DDT isn’t always bad. In malarial regions (which are expected to expand substantively with global warming), indoor residual spraying (of eves and ceilings) is an important component of malaria control, saving thousands of lives every year. Presently, the human health risks and benefits of indoor DDT spraying balance out on the side of continued application [1]. But there is growing concern for human health risks, even when DDT is applied properly. And in the long-term, the equilibrium level of malaria cases, despite indoor residual DDT use, remains at relatively high levels.

Recently, there has been a breakthrough in malaria control [2]. Researcher Stephen Hoffman engineered weakened sporozoites via irradiation in situ in the mosquito host. The sporozoites were extracted by dissection, and administered intravenously to a test cohort of 40 people. At the highest vaccine dose, 100% of the test subjects were successfully protected from malaria. 

Logistically, this vaccine still leaves us quite a distance from the finish line of effective malaria control. Dissecting sporozoites from individual irradiated mosquitoes is a clear impairment to wide use. As is the IV administration, and the need for five sequential doses. 

Still, as Anthony Fauci points out in the Post piece, these are engineering problems. They are solvable by technological means. This is as close as we’ve gotten to a workable malaria vaccine. The concept is simple and robust. We’re only separated from a viable vaccine by scale-up challenges, which are, admittedly, formidable. Still, the human costs of malaria globally are enormous. Addressing those costs, and the prospect of reducing DDT use in indoor residual spraying, are important incentives. This is an opportunity we cannot afford to pass up. We must pursue this vaccine, and pursue it hard. 

Notes

[1] See Bouwman et al. 2011 at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3114806/

[2] reported by Michael Gerson, op ed “Closer to a Malaria Breakthrough?” in the Washington Post13 August 2012. 

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