Yes, the DDT ban myth is back, this time in “DDT Returns” by Apoorva Mandavilli that reads like a press release by DDT advocacy group Africa Fighting Malaria. It’s in Nature Medicine of all places and is subscription only, but because I’ll be quoting the bits that are wrong or misleading you’ll see most of it:
After decades of being marginalized as a dangerous pesticide, DDT–short for dichloro-diphenyl-trichloro ethane–is set to be reintroduced into countries that have tried, and failed, to win the fight against malaria.
On 2 May, the United States Agency for International Development (USAID), arguably the most powerful donor agency in the world, endorsed the indoor spraying of DDT for malaria control.
This isn’t a change in policy. In November last year USAID said
USAID strongly supports spraying as a preventative measure for malaria and will support the use of DDT when it is scientifically sound and warranted.
But the DDT ban myth peddlers cannot be stopped by mere facts. Mandavilli:
USAID never banned DDT outright, for instance, but nor did it fund DDT’s purchase–which amounts to the same thing. For that reason, the May announcement is widely seen as a change in policy even though the agency doesn’t position it as such.
USAID can’t win. If they say they support DDT use they’re lying. If they fund its use then they changed their policy. Nothing they say or do can stop the DDT ban myth.
The World Health Organization (WHO) is set to follow. In its new guidelines, a final version of which is expected to be released later this summer, the WHO is unequivocal in its recommendation of DDT for indoor residual spraying.
Of course, in the old guidelines the WHO was also unequivocal in its recommendation of DDT for indoor residual spraying. They state:
WHO recommends indoor residual spraying of DDT for malaria vector control.
Later in the article Mandavilli even mentions this fact:
The WHO recommends 12 insecticides including DDT–which is an organochlorine–six pyrethroids, three organophosphates and two carbamates.
But the DDT ban myth is immune to mere contradictions.
For these impoverished countries, the choice may seem clear: DDT is cheap and lasts longer than other pesticides, so it has to be sprayed less often. Most pesticides work by killing mosquitoes on contact, but DDT also repels them.
“DDT is the most effective chemical, the most effective insecticide in terms of malaria,” says Arata Kochi, director of the WHO’s Global Malaria Programme.
That’s rather an oversimplification, according to the
latest publication from … WHO’s Global Malaria Programme.
However, the success of IRS depends largely on the mosquitoes resting
indoors before or after feeding — not all species do this naturally
and the excito-repellency of DDT and pyrethroids may dissuade
mosquitoes from resting long on sprayed surfaces. Other requirements
include the need that human shelters have walls to be sprayed, access
to the interior of all houses, and a relatively stable human
population without a high frequency of replastering of sprayable
surfaces. The conditions for “eradication” were not met in all malaria
areas, especially in Africa, where serious efforts were never mounted.
So the repellency effect of DDT makes it less effective. And in Africa DDT is not so much returning, but being used seriously for the first time. The WHO report goes on at length on the different methods of vector control. There isn’t one best method. It depends on the vector, infrastructure support, nature of dwellings, insecticide resistance and on and on. Here’s a taste:
In areas where malaria vectors are fully susceptible to pyrethroids, sideby-side comparison of the same pyrethroid used for both methods against
malaria transmitted by An. gambiae s.s. and An. funestus showed very similar
impact on the entomological inoculation rate (EIR) of the vector population,
incidence of malaria infection and malaria morbidity in children. A review
of the remarkable results achieved in the 1950s, 1960s and 1970s with IRS
in highly endemic areas of Africa shows that so far none of the recent ITN
trials has done as well. However, IRS programmes were larger in scale than
the relatively smaller ITN efficacy trials, so the comparison conflates two
methods and scales of intervention.
Cost comparisons of IRS and ITNs yielded surprisingly variable results.
The encouraging past results with IRS in tropical Africa did not lead to
nationwide campaigns. It can be argued that this has been because in
very low income countries it is not possible routinely to meet the logistical
demands of ensuring that trained spray teams equipped with working
spray pumps and sufficient insecticide arrive at each village in time to spray
before the malaria season. It can also be argued that it is more feasible to
supply ITNs in such circumstances because this does not impose similar
Moreover, the experience of long-term use of IRS by organized antimalaria
campaigns in many parts of the world has frequently shown a progressive
development of people’s fatigue and reluctance to allow intrusion into
their homes. This phenomenon may be less likely to occur with the use
of ITNs, which are far more under the control of households. In contrast,
in rapid response to epidemics there are good reasons to favour a trained
and equipped IRS “fire brigade” capable of moving quickly to an area
where there is a high likelihood of a malaria epidemic unless quick action
Mandavilli then goes in for the traditional Rachel-Carson-worse-than-Hitler gambit.
Between 1955 and 1969, the Global Malaria Eradication Campaign also relied heavily on DDT. In Europe, India, South America, Africa, wherever it was used widely, DDT cut malaria rates dramatically and saved millions of lives.
Then came Carson’s Silent Spring– credited with launching the environmental movement–which famously described DDT’s horrific effects on the food chain, and the stark silence left behind by dying birds. The book was so effective that to this day, any mention of DDT instantly evokes images of bald eagles and thinning eggshells.
DDT soon became a symbol of Western governments’ rash embrace of science. In the US and in Europe, environmental groups waged a successful campaign against the pesticide. Based largely on its effect on the environment–and on public opinion–the US Environmental Protection Agency in 1972 banned DDT. Norway and Sweden had begun the trend in 1970, and the UK signed on in 1986.
Environmental groups that still oppose DDT see its use in developing countries as a double standard. On the other hand, note champions of DDT, most of those groups are based in countries where malaria is only a distant memory.
“I think the whole push of the environmentalists like Rachel Carson and many others to eliminate all uses of DDT are, quite honestly, responsible for millions and millions and millions of human deaths,” says Don Roberts, professor of tropical public health at the Uniformed Services University of the Health Sciences in Maryland.
This misrepresents Carson. She opposed the indiscriminate use of DDT and warned that overuse would cause insect resistance and make it useless. The restrictions on the agricultural use of DDT that she helped inspire have prevented the development of resistance and are the reason why it can still be used today in many places to fight malaria. In short, she prevented many deaths from malaria.
And who are these environmental groups that oppose DDT use? Neither Greenpeace nor the World Wildlife Fund oppose its use.
Most African nations are heavily dependent on foreign aid and can ill afford to cross a line drawn by donor agencies.
The World Bank went one step further, making the ban of DDT a condition for loans.
Far from banning DDT, the World Bank
funds DDT in Eritrea, India, Madagascar and the Solomon Islands.
The WHO supported the use of bednets dipped in insecticide over indoor spraying, even though malaria rates continued to increase.
Yes, they support bed net use because there is a mountain of evidence showing that bednets are effective. See the WHO report linked above. This sort of reporting is pernicious, because it misleads readers into thinking that bednets don’t work.
“People are very emotional about DDT, even within the WHO,” Kochi says, adding that much of the reaction to DDT was a response to political pressure.
Yeah, no kidding. The Rachel-Carson-worse-than-Hitler brigade want to exploit the issue to bash environmentalists. Hence the weird focus on DDT. You’d think that anti-malarial drugs, other insecticides and other means of vector control don’t exist.
Usually these sorts of pro DDT articles ignore resistance, so I should note that Mandavilli at least mentions it:
Unless done well, however, using DDT may be dangerous–and powerless against malaria.
For spraying to be effective, at least 80% of the affected area must be covered. Global agencies must first map the distribution and behavior of different kinds of mosquitoes and, most important, patterns of resistance to insecticides. “The last thing you want to do is select for resistance,” says Coetzee.
Hey yeah, that’s what Rachel Carson was saying…