Sunday, June 19, 2005


John Quiggin takes exception to a recent post by Rafe Champion and an article by Miranda Devine, citing factual error:
DDT has never been banned in antimalarial use. The main reason for declining use of DDT as an antimalarial has been the development of resistance. Antimalarial uses have received specific exemptions from proposals to phase out DDT, until alternatives are developed. Bans on the use of DDT as an agricultural insecticide, promoted by Rachel Carson and others, have helped to slow the development of resistance, and therefore increased the effectiveness of DDT in antimalarial use (links on this here)
Quiggin bases his assertion, that DDT use declined due to the development of resistance, on a letter to the the Australian by Dr Alan Lymbery and Professor Andrew Thompson in response to an article by Christopher Pearson. Well fellas, you've got it wrong, DDT use declined mostly because of pressure from environmentalists.

Anyone doubting that pressure from environmentalists created a de facto DDT ban should check the ample evidence at Malaria Foundation International. Take as indicative the following excerpts from DDT house spraying and re-emerging malaria as published in the Lancet of 22 July 2000:
Even in the earliest field studies, DDT showed spectacular repellent, irritant, and toxic actions that worked against malaria vector mosquitoes.10 When DDT was sprayed on house walls (2 g/m2) it exerted powerful control over indoor transmission of malaria.11 As a consequence, house spraying produced excellent and rapid results in 1943 in the Mississippi Valley, USA, then in Italy, Venezuela, Guyana, India, and several other countries. House-spraying programmes functioned as national malaria-eradication services. The strategy encompassed vector control and case-treatment campaigns during the attack phase (3-5 years), followed by case treatment to eliminate the remaining parasites during consolidation and maintenance phases. As such, it was a multifaceted approach to disease control. Most countries adopted the malaria-eradication strategy that was formulated and coordinated by WHO. Colonial Africa was left out of the "global" programme because of the lack of national structure and expertise. Even so, some African countries (South Africa, Zimbabwe, and Swaziland) developed successful national eradication programmes. Although malaria transmission could not be stopped by DDT in some areas such as the wet savannas of West Africa,12 the overall effect of vertically structured programmes for applying DDT to house walls was an almost complete reduction or elimination of malaria.11,13,14. For example, malaria was eradicated from most of North America and Europe, and strong decreases in prevalence were seen in the Mediterranean Basin, the Middle East, the Far East, and even in southern Africa.


Since the early 1970s, DDT has been banned in industrialised countries and the interdiction was gradually extended to malarious countries. The bans occurred in response to continuous international and national pressures to eliminate DDT because of environmental concerns. Global trends of decreasing numbers of sprayed houses started with changing strategy from the vector-control approach to malaria control. Despite objections by notable malariologists18 (also Arnoldo Gabaldon19), the move away from spraying houses was progressively strengthened by WHO's malaria control strategies of 1969, 1979, and 1992. These strategies were adopted even though published WHO documents and committee reports have consistently and accurately characterised DDT-sprayed houses as the most cost effective and safe approach to malaria control.12,20-22 Changing the emphasis on house spraying was further strengthened by a WHO plan, first introduced by the Director General of WHO in 1979,23 to decentralise malaria-control programmes. This plan was adopted in World Health Assembly Resolution 38.24 in 1985.24 From then on, for countries to qualify for foreign or international assistance, they were expected to comply with WHO guidance on house spraying and to incorporate malaria control programmes into primary health-care systems. Additionally, assistance from industrialised countries was often specifically contingent on not using DDT.

Other mechanisms also have been used by environmental advocates to stop use of DDT for malaria control. A recent example is the agreement of the North American Commission for Environmental Cooperation (CEC) that forced Mexico to stop producing and using DDT for malaria control.25 This agreement also eliminated a rare source of DDT for malaria control in other countries in South America. Claims by environmental advocates26 that Mexico is "now" a test-bed for a new model of "malaria control without DDT" ignores the simple fact that Mexico is a developed country (ie, it is one of the richest of malaria-endemic countries). Consequently, years from now, the outcome for Mexico will show how a scientifically and economically rich country can or cannot control malaria without DDT. Even if Mexico is successful in maintaining control of malaria without use of DDT,27 this success will not be relevant for countries with serious malaria problems and the methods used may not be useful or affordable in more needy and scientifically impoverished countries.

On a landscape scale, a sprayed house will only have a very small amount of DDT enclosed in the walls. Nevertheless, environmentalists are still seeking a global ban26,28,29 arguing that if DDT is produced for use in improving public health, it will also be used for agriculture and lead to global pollution of the environment.26,27 This instance of environmental advocacy seems to have won approval of powerful pesticide companies because it allows them to sell their more expensive insecticides. The replacement of DDT by organophosphate, carbamate, or pyrethroid insecticides is commonly proposed even though price, efficacy, duration of effectiveness, and side-effects (eg, unpleasant smell), are major barriers to their use in poor countries. High costs and downward trends in foreign assistance discourage many countries that cannot afford the switch to DDT alternatives. Although arguments can be mounted on both sides of the issues of cost-effectiveness, duration of activity, and safety of alternative insecticides, there should be no confusion about what happens to public health when use of DDT is banned.
There are other sources at Malaria Foundation International making similar reference to pressures from environmentalists.

It is worth noting that the Lancet article linked above states that there was at the time writing in 2000 a "ban" on the use of DDT. The article also describes the consequences of this "ban":
When a malaria-endemic country stops using DDT, there is a cessation or great reduction in numbers of houses sprayed with insecticides, and this is accompanied by rapid growth of malaria burden within the country.1,12,17 DDT house spraying was stopped in Sri Lanka in 1961, and this was followed by a major malaria epidemic. Since then, numerous epidemics have occurred in many countries, after suspension of DDT house treatments, such as Swaziland (1984) and Madagascar (1986-88), where malaria killed more than 100 000 people. In both cases, the authorities restarted DDT house spraying and stopped the catastrophic epidemics.8 In Madagascar, malaria incidence declined more than 90% after just two annual spray cycles. Today, few countries still use DDT and most have no way to even buy this insecticide. Without DDT, malaria rates are returning to those seen in the 1940s, affecting additional millions of infants, children, and adults.

WHO's Global Malaria Control Strategy (GMCS)30 of 1992 and the current Roll Back Malaria31 initiative emphasise treatment of cases and protection of people with impregnated bednets. The failure to include DDT house spraying results from antagonism between the horizontal medical structures and the vertical ones that are needed to restart house-spraying programmes. In other words, more is involved than some undefined opposition to use of DDT. Additionally, some sponsors make the banning of DDT a condition of their support and also require that malaria control be done within a primary health-care system. Because of these multiple factors, the GMCS or Roll Back Malaria initiative, as formulated, will not stop progression of the ongoing global resurgence of malaria.
Clearly, the authors of this article think opposition to the use of DDT has had dire consequences.

On the DDT issue the smarter-than-thou brigade is, of course, wrong and should shut the fuck up.

Update: For the latest on Quiggin, go here.


Post a Comment

<< Home