Jessie Stone, who runs a malaria education, prevention and treatment program in Uganda, comments in the New York Times on the WHO's DDT pushing.
To many of us in the malaria-control business, it came as no great surprise last week when the World Health Organization recommended wider use of DDT in Africa to combat the mosquitoes that cause the disease, which kills more than a million people a year, most of them children in Africa.
The W.H.O.'s endorsement of DDT for spraying inside houses has the support of Congress and the Bush administration. With the W.H.O.'s encouragement, several African nations have approved DDT for use in indoor residual spraying (that is, spraying the walls of huts to kill the mosquitoes that wait there until dark). Uganda's Ministry of Health and National Malaria Control Program, for example, have embraced this approach. ...
Although DDT helped eliminate malarial mosquitoes in South Africa, the case was unique -- that type of malaria was directly related to the length and intensity of the rainy season, when malarial mosquitoes are active -- and we still don't know the broader impact of its use there. In the African countries where the burden of malaria is greatest, the disease is endemic. Uganda, where it rains throughout the year, could not be more different from South Africa in terms of malaria, and it is a mistake to apply the same formula here. The use of DDT for indoor residual spraying will not produce the same results and will almost certainly have dire consequences.
And spraying is costly. This year in Kabale, in southwestern Uganda, 100,000 huts were sprayed as part of an indoor spraying project. A permethrin derivative, not DDT, was used and the spraying was controlled and safe. The cost was close to $2 million. ...
DDT is not the magic bullet that will eradicate malaria. We need to refocus resources and attention on something most Africans do not have: basic malaria education, and prevention with insecticide-treated bed nets.
So is there a scientific evidence for using DDT spraying instead of insecticide-treated bed nets in Uganda? The International Water Management Institute recently published a study on DDT use in Uganda and three other African countries.
Malaria control decision makers who use or want to use DDT to combat
malaria say they want to use it because it is both effective and
inexpensive, when compared to alternatives. With budgetary constraints
faced by the Ministries of Health, these decision makers find it
necessary to use the least expensive option for vector
control. However, none of the malaria control or insecticide control
specialists in Ethiopia, Uganda, Kenya or South Africa could cite a
formal cost-effectiveness study to assess whether IRS using DDT was,
in truth, the most effective and inexpensive method to be used. ...Compared to other countries, the issue of DDT reintroduction is
extremely controversial in Uganda. The Ministry of Health's plans to
reintroduce DDT is raising concerns in the country's scientific
community. Most Members of Parliament support the move to reintroduce
DDT for malaria control, although there are some strong dissenters
(Mubiru 2004). The Ministry's initiative is driven by government
elites, rather than malarious communities themselves; the general
population of Uganda is not particularly adamant about the DDT issue. ...In April 2004, the African Network for Chemical Analysis of Pesticides
(ANCAP) held a workshop in Kampala, Uganda on the appropriateness of
DDT, considering the malaria crisis and Uganda's capacity to control
hazardous chemicals. According to one workshop attendee, the keynote
address, given by the Minister of Health, indicated that DDT would be
reintroduced into Uganda regardless of the outcome of the workshop. ...IRS is typically used to prevent epidemics; however, Uganda's Malaria
Control Programme has recently promoted IRS in structures where ITNs
are not used, "regardless of level of endemicity" (Uganda Ministry of
Health 2001). ...
They conclude:
Often, research is either lacking or ill incorporated into vector
control policies. In East Africa in particular, better links to
research organizations, as well as development of government research
capacities, should be pursued to increase the robustness of future
vector control policy decisions. Interestingly, the immediate impact
of the POPs Treaty has been to legitimize government policies to use
or reintroduce DDT for malaria vector control.
So is there any research that supports DDT use in Uganda? Uganda's Ministry of Health has just put out an Environmental Impact Statement. In the executive summary they say that a cost-benefit analysis supports DDT use:
The cost-benefit ratio of DDT compared to ACT and HOMAPACK is 24.9
and 18.7 respectively. For deltamethrin the ratios were 10.0 and 7.5
while for ICON it is 14.56 and 10.9 respectively.
Well that sounds good, but the WHO's recent position paper says
Currently, the cost of using some of the pyrethroid insecticides is almost equivalent
to that of using DDT,
How did the MOH EIS come up with deltamethrin being 2.5 times as expensive as DDT? They write:
However, information on the relative cost of DDT and other
insecticides is scarce. The team failed to get price quotations of the
currently used insecticides for mosquito control for IRS from Twiga
Chemicals. However, WHO (1990) based its calculations on the prices of
the late 1980s and early 1990 to compare all the insecticides in use.
Their price comparison was based on the 1990 price of deltamethrin of $800/kg. I found a current price of $300/kg on the web, so the cost of IRS with deltamethrin would be pretty close.
They also compare IRS with DDT to bed nets and conclude (page 97) that the five year cost of DDT spraying for the whole country would be $476,789 while long-lasting nets would be $146,400,000, i.e. 300 times as expensive. Unfortunately there are are some mistakes in their calculations and their ratio is wrong. By a factor of 1,000. Their table says that DDT spraying costs $0.0186 per household per year. Elsewhere they give the numbers this is based on: a DDT cost of $4.65/kg, 200 m2 to spray per house and 2gm/m2 DDT every six months. That's $4.652000.002=$1.86 per six months, $3.72 per year. They understated the DDT cost by a factor of 200. While for long lasting nets they assumed that a new net was needed every year when these nets last for about five years, so they overstated the cost of nets by a factor of 5. Correcting for these factors you find that instead of nets being 300 times as costly, they are actually much cheaper -- only 30% of the cost of spraying DDT.
Now it may be that increasing DDT use instead of nets is the most effective means for control of malaria in Uganda. But there is no scientific evidence for this and it would be wise to experiment with a pilot program before spending many millions of dollars on a massive spraying program.
Tim, your numbers for DDT and bed nets (or at least the ratio of the two) are in line with a study done on the relative costs of bed nets vs DDT house spraying by the Ministry of Health and Medical Services Solomon Islands.
The ratio of the per capita cost for DDT spraying to the per capita cost of bed nets that they came up with was about 2.21 (ie, DDT spraying 2.21 times as costly as permethrin-impregnated bed nets).
Though the actual cost of each method will vary from place to place, there is no reason to expect that the ratio of the two would be all that different from one place to another.
As the study authors point out, the study looks at cost only, not effectiveness.
Tim, your numbers for DDT and bed nets (or at least the ratio of the two) are in line with a study done on the relative costs of bed nets vs DDT house spraying by the Ministry of Health and Medical Services Solomon Islands.
The ratio of the per capita cost for DDT spraying to the per capita cost of bed nets that they came up with was about 2.21 (ie, DDT spraying 2.21 times as costly as permethrin-impregnated bed nets).
Though the actual cost of each method will vary from place to place, there is no reason to expect that the ratio of the two would be all that different from one place to another.
As the study authors point out, the study looks at cost only, not effectiveness.
tim,
i think you should read:
Author(s): Ioannidis JPA
Source: PLOS MEDICINE 2 (8): 696-701 AUG 2005
this is a clear example of an author in the peer-reviewed press pointing out that epidemiology studies with a low relative risk (i.e. less than 3) are more likely to lead to false results.
Ioannidis is a statistician and epidemiologist, with an outstanding publication record. I thought that you might wish to reconsider some of your comments about Brignell being a crank for making similar statements.
yours
per
Oy vey!
Everybody has read that paper by now per. If you have a relevant point to make here, where Tim has once again done what he does best and shown quickly, simply and elegantly what absurd conclusions people can draw when they "think" with their faith system and their ideology, or because they're being paid to believe stupid things, you might care to try to make it. Everybody's read Ioannidis by now - and no I wasn't stunned as by a bolt from the blue by the demonstrations of the paper, which is good value - but what is your point?
Tim has once again done what he does best and shown quickly, simply and elegantly what absurd conclusions people can draw when they "think" with their faith system and their ideology...
tim denounced Brignell as a crank, and claimed "You won't find support for Brignell's claim in any conventional statistical text or paper".
well here is a paper which provides strong support for brignell's view. I think there are many such, making similar points, and they have been in the literature for many years.
I am just wondering if Tim will accept that what he said was wrong.
yours
per
This is a tacit admission then that your reference to Brignell is off-topic? OK. I remember at the time that I decided for myself that Brignell was, if not a quack and crank, then certainly someone with an inflated sense of his own abilities in the subjects he was being very noisy about. I recall him referring to somebody else's website on atmospheric physics as though it were GodZoneTruth or similar, whereas my considered judgment on it was that it was illconceived denialist nonsense at best. But I also recall thinking that I'd seen plenty of worse efforts than Brignell's on the whole, and that a bit of modesty may have been mostly what he was missing. (And perhaps I'm generous to a fault :)
Why are we talking about him? What is the good reason for mentioning the Ioannidis paper in the context of this posting?
Don't you know it's all about the Lancet paper? The title of this post says "Blah Blah LANCET PAPER Blah.:
Why are we talking about him?
beats me. I made my comment clearly to tim, and I made no bones it had anything to do with DDT !
if you want to return to topic, you could enquire as to the relative toxicity of DDT, and the compounds it competes against. But I don't think tim will exercise his attention on that...
yours
per
"I made my comment clearly to tim"
There's this thing called e-mail, whereby you can send a message directly to the person you are addressing.
It's really quite remarkable. Sure beats talking to yourself (or to sock puppets), at any rate.
Sounds like the Uganda Ministry of Health has already come up with a strategy to control malaria within their country.
One would hope that organizations like WHO would not be in the business of deciding what the best approach for malarial control is for all countries.
Imposing retrictions on the approaches individual countries can take to malaria control -- eg, decing what the "best" method is and then insisting that all (or a certain fraction of) allocated money be spent on that particular method -- is probably not the best approach.
Unfortunately, some outside officials have a tendancy to treat people in the developing countries as if they were children, not capable of making informed decisions for themselves.
Some of these countries (like Uganda) even have their own highly educated health experts (even their own universities for training such experts, if you can imagine).
There appear to be some muddles in various of the above posts, eg between capital costs (bednets) and recurrent cost (spraying), and relative coverage costs, both per person and per household, and per hour. For households, you need to multiply the per bednet cost by 6 or 7, given average houshold size in sub-Saharan Africa, whereas a single house spray protects the whole household at least while they are indoors at night. Bednets are great when all are in bed, but not all go to bed at sunset (the most dnagerous time) and stay there till dawn, also an active period for malarial mosies. Thus bednets are necessary but not sufficient for total household protection at night. I see that there have been studies cited on earlier threads that do show the superior cost effectiveness of DDT but of course they have been disregarded by all except the heroic per.
Bednets that last five years are a recurrent cost. The EIA gave the bednet cost as per household. If it's per net, that's another mistake they made. In any case, poor African households do not have 6 or 7 beds -- Jessie Stone, who runs a malaria education, prevention and treatment program in Uganda [says](http://www.nytimes.com/2006/09/22/opinion/22stone.html?ex=1316577600&en…)
>DDT is not the magic bullet that will eradicate malaria. We need to refocus resources and attention on something most Africans do not have: basic malaria education, and prevention with insecticide-treated bed nets. A mosquito net costs $6.50 and can last up to five years. An average of three people can sleep under it, and the only harmful effect we have heard about, after having distributed 11,000 nets in the Kamuli, Jinja and Kayung districts over the last two years, is people being hot at night.
Using her figures that suggest two nets per household, bednets are still significantly cheaper than spraying DDT. Feel free to cite any studies that show that DDT is more cost effective. You should also send your cites to the WHO, who don't seem to know about them.
Tim Lambert: here's the citation, I think it is also mentioned above but evidently unread: "Impregnated nets or DDT residual spraying?:, Mead Over et al., Am. J. Trop. Med. Hyg. 71 (2 suppl), 2004, 214-223.
Your comment also evades the issue: what protects after dark when the anopheles is most active if one is not in bed under bednet?