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Exit strategy for conquering African malaria

May 22, 2014 - 21:30 -- William Jobin

If we limit ourselves to the conventional approaches to fighting malaria - drugs, bednets and biocides - the future looks bleak. It looks like an endless war. The war started about 1950 when DDT and chloroquine looked like perfect weapons. But since then the development of resistance has shown us how ephemeral they were. The mosquitoes began to eat DDT for breakfast, and the malaria parasites learned to swim in chloroquine. Historians are showing us that malaria has incredible tenacity in Africa. We long for a solution to this horrible problem - an Exit Strategy. Unfortunately WHO, USAID and the UN agencies offer us nothing but more of the same - and with declining budgets.

For the past few decades there has been an implicit but mythical Exit Strategy for the fight against malaria - the development of a vaccine. This implied weapon has been the stimulus for enormous amounts of immunological research, and has also given solace to field workers who see the disastrous brick wall of drug and biocide resistance coming again soon. The repeat of this historic disaster will mean that once again indoor spraying of biocides becomes exceedingly expensive, that treated bednets will no longer give protection, and that the current drugs will be useless. It is a grim picture, unless one has an Exit Strategy. Relying on the mythical vaccine is simply an exercise in fantasy.

Fortunately there is a practical Exit Strategy available, using proven methods that require little technology. Perhaps the lack of technology is the reason why this weapon has not been pursued by our scientific and medical elite; it is too mundane. This realistic Exit Strategy features (1) shovels for digging drainage ditches and filling swampy sites of mosquito breeding, (2) window screens and (3) affordable electricity for fans that make sleeping bearable in screened houses. Unlike the current vaccines being studied, drainage from shovels, window screens and affordable electricity are durable, and do not require re-application every few years. And we already have them all over the world. Farmers all over Africa know how to drain swamps with shovels. Carpenters all over Africa already know how to screen in houses, after blocking the eaves with heavy paper or papyrus. Affordable electricity is growing at the rate of 4.1% per year in Africa, as new fuel and hydropower sources are developed faster than anyplace in the world (Christian Science Monitor 2013.)

As affordable electricity becomes available, people can close up their houses tight at night and use small electric fans for comfort. The fans also disturb the hunting behavior of the female anophelines. Note that countries with available and affordable electricity do not have malaria. Turkmenistan and Mauritius have recently been added to the list, the Tennessee Valley of the USA was on the list by 1950. The TVA was developed to provide electricity to rural communities.

What basis is there for confidence in this practical Exit Strategy? Simply the experience in all the northern countries where physicians no longer know what malaria looks like. The historian Snowden documented the gradual disappearance of malaria from Italy after the Second World War; largely before the advent of DDT and chloroquine (Snowden 2006, and Jobin 2010). These cheap chemicals used to be thought of as the Exit Strategy in the WHO Eradication Program – until they hit the brick wall of chemical and drug resistance the first time, about 50 years ago.

Another important feature of this practical Exit Strategy is that it has multiple benefits, while a vaccine would be highly specific not only for one disease, but even for only one strain of that disease. A vaccine against Plasmodium falciparum, the most prevalent killer in Africa, would not protect against Plasmodium vivax, also a common killer in most of the tropical world.

The multiple benefits of eliminating swamps and breeding sites has been shown in Tanzania to also control some other species of mosquitoes which transmit filariasis (Castro 2010). Screening of houses also keeps out houseflies which are important in transmission of cholera and other severe diarrheal diseases. Screening of houses also increases the resale value of houses, in a way that biocide spraying could never do. Buying shovels and picks to drain a swamp gives you tools to use in growing crops as well. This Exit Strategy has multiple benefits, always a winner.

What about costs of this practical Exit Strategy? It is hard to compare anything with the cost of a mythical vaccine because none exists yet, except a recent one that gives protection to only one-third of the people injected, and would probably have to be boosted every 1-3 years. The short-term impact of this vaccine almost seals its fate as an impractical tool in Africa, but in any event it would be incredibly expensive.

The cost of digging a ditch or installing screens on your house is low, especially if you do it yourself. For comparison, we would want it to be cheaper than the current chemically-based strategy of WHO and the US PMI, based on drugs, bednets and biocides. The most recent data from PMI indicate that spraying a house in Africa costs at least $7 per person protected, by a spray that was effective for about 3 months (Jobin 2012). To give year-round protection in a house with a family of 6 would cost $168 per year.

If screens were installed that lasted 10 years, if they cost less than $1,680 they would be competitive with spraying. And this comparison neglects the cost of drugs and bednets. So screens look pretty good, especially if you do the work yourself and only have to buy the metallic screen material, some light lumber, and heavy paper to seal the eaves. Likewise if you drain the swamps and depressions around your house, you could get some pretty good picks, hoes and shovels for $1,680. This is where community efforts make the practical Exit Strategy even more feasible, as you could share these tools with your neighbors.

So I have a suggestion. Let us focus on communities in the midst of the malaria battle, and offer them an Exit Strategy that they can implement themselves. Then when WHO and the Global Fund fail, when mosquitoes learn to coexist with pyrethroids, and when ACT is no longer effective, the communities can continue the fight.

There is another aspect of economic development to consider. In the northern countries, malaria disappeared as their economies progressed. But since economic progress is going slowly in Africa, do we want to wait?

Perhaps there are two options then. One is to wait until the countries progress enough that malaria gradually gets eased out by improvements in housing, education, literacy and health services.

The second option might be to jump ahead with a vertical malaria control program, assuming that economic development is being held back by malaria, and thus would proceed faster if malaria were suppressed. We have published data recently which supports this idea. In fact every dollar invested per capita in malaria control resulted in $6 increase in per capita GDP in the countries protected (Jobin 2014).

Is the second option viable? How much could we invest in suppressing malaria in hope of a payback in the near future?

Refs:

Castro et al 2010 The importance of drains for the larval development of lymphatic filariasis and malaria vectors in Dar es Salaam, United Republic of Tanzania. PLoS Negl Trop Dis. 2010 May 25;4(5)

Christian Science Monitor 2013, Mike Pflanz, January 1. Boston, USA

Jobin 2010 A realistic strategy for fighting malaria in Africa, Boston Harbor Publishers, Massachusetts, USA

Jobin 2012 Improving the US Presidential Malaria Initiative, Boston Harbor Publishers, Massachusetts, USA

Jobin 2014 Suppression of malaria and increases in economic productivity in African countries.....MWJ 2014, 5,4

Snowden 2006 The conquest of malaria, Yale University Press, New Haven, USA