The New York Times reports:
Dr. Kochi said the most substantive change in the W.H.O.’s guidelines on the use of insecticides would extend the reach of the strategy. Until now, the agency had recommended indoor spraying of insecticides in areas of seasonal or episodic transmission of malaria, but it now also advocates it where continuous, intense transmission of the disease causes the most deaths.
Dr. Kochi’s new policies and abrasive style have stirred the small world of malaria experts. Dr. Allan Schapira, a senior member of the W.H.O. malaria team who most recently oversaw its approach to insecticide spraying, resigned last week.
Reached Thursday on his cellphone, Dr. Schapira declined to comment on his reasons, except to say that they were professional. He did not return messages left Friday.
His successor, Pierre Guillet, a medical entomologist, said Dr. Schapira quit because he was uncomfortable with the new approach on insecticide spraying.
There are fierce debates among experts over when it is best to use indoor spraying or mosquito nets impregnated with insecticides that last up to five years, though most agree that both spraying and nets are important tools.
Dr. Kochi said in an interview that half the professional staff of the W.H.O.’s malaria program has left “one way or the other” since he took over in October. He described Dr. Schapira as the “main brain” behind the past approach.
“He was professionally insulted by me,” Dr. Kochi said.
In answer to a question, Dr. Kochi acknowledged that he had indeed told members of the staff in meetings that they were stupid. “They are very inward looking, and they do not communicate outside the malaria field,” he said. “It’s ridiculous.”
Dr. Kochi earlier headed the W.H.O.’s tuberculosis campaign until he was forced out after his blunt manner alienated important partner organizations.
So Kochi, coming from outside the malaria field, reckons he knows more about it than the people in the field. Well, that’s possible, but the press release he put out does not inspire confidence:
WHO actively promoted indoor residual spraying for malaria control until the early 1980s when increased health and environmental concerns surrounding DDT caused the organization to stop promoting its use and to focus instead on other means of prevention. Extensive research and testing has since demonstrated that well-managed indoor residual spraying programmes using DDT pose no harm to wildlife or to humans.
The fact is that until 1994, DDT was the WHO’s insecticide of choice for malaria vector control. One of the reasons that it was downgraded to just be one of the recommended insecticides was the evidence of possible health risks to humans. Since then there has been more evidence of health risks. Malaria is far more damaging to the health than any risks from DDT, but this is a reason to consider other insecticides if they are as effective as DDT.
Nor did WHO stop promoting DDT. Similar claims have been made by Senator Tom Coburn, who said
The WHO and other elites have stigmatized DDT
And Richard Tren of Africa Fighting Malaria, who wrote:
The World Health Organization, World Bank and United Nations Environment Programme are all against the use of DDT
Alan Schapira rebutted such claims in November 2004:
WHO has never given up in its efforts to ensure access to DDT where it is needed.
“DDT has become a fetish,” adds Allan Schapira of WHO. “You have people advocating DDT as if it’s the only insecticide that works against malaria, as if DDT would solve all problems, which is obviously absolutely unrealistic.”
And the WHO’s 2004 statement on ITNs (nets) vs IRS (spraying) clearly supports IRS in regions of unstable transmission:
For example, in some countries, especially in Southern Africa and in the Horn of Africa, proportions of the population are exposed to unstable or epidemic malaria. In these circumstances, IRS has some important advantages: it has rapid and reliable short-term impact, and it can be targeted to the communities at highest risk, on an annual basis and in response to changing transmission patterns. IRS is, on the other hand, relatively demanding in terms of the logistics, infrastructure, skills, planning systems and coverage levels that are needed for a successful and effective operation. Nevertheless, such systems have been successfully and effectively maintained for many years in some African countries, especially those that contain large populations exposed to unstable malaria. Every effort should be made to sustain these systems in the future.
Unfortunately the falsehood in the WHO press release led to this sort of inaccurate reporting: (from Australia’s ABC)
DDT, the long-banned insecticide blamed for killing birds and other wildlife, is now approved for use indoors to fight malaria, says the World Health Organization.
But it gets worse. The press release continues:
“Indoor spraying is like providing a huge mosquito net over an entire household for around-the-clock protection,” said U.S. Senator Tom Coburn, a leading advocate for global malaria control efforts. “Finally, with WHO’s unambiguous leadership on the issue, we can put to rest the junk science and myths that have provided aid and comfort to the real enemy — mosquitoes — which threaten the lives of more than 300 million children each year.”
And later even quotes Richard Tren. No wonder so many of the WHO’s malaria experts resigned. Instead of trying to knock some sense into Coburn’s head, Kochi threw his own malaria experts to the wolves.
But hey, despite all this maybe there is some science behind the new policy? Let’s check. WHO’s 2004 statement on ITN vs IRS in areas of stable transmission:
However, in most countries of Africa south of the Sahara, the vast majority of the rural population is exposed to stable malaria and the systems needed for large-scale IRS do not exist. In these countries, the critical question is not whether one intervention is slightly more powerful than the other, but which of the two offers better prospects of achieving high nationwide coverage and long-term sustainability. In these circumstances, ITNs have important advantages. As well as being less demanding than IRS in terms of infrastructure and organization, ITNs allow vector control resources to be targeted toward those most at risk in stable endemic settings, i.e. pregnant women and young children, hence best use can be made of initial resources. ITNs protect people who use them, and they also have community level benefits, giving protection to people without nets in nearby houses. These benefits are thought to increase incrementally with coverage, across all coverage levels, and will contribute to early gains in equity as programmes scale up. The minimum coverage at which ITNs might have a significant community effect at programme level is not yet established. ITNs can give protection of longer duration than IRS since a net in good condition gives reduced but still significant protection to the user even after the insecticide has worn off. This advantage will be further strengthened by the emerging development of Long Lasting Insecticidal Net (LLIN) technology, which greatly extends the effective life of the insecticide.
And the report from the WHO Study Group on malaria vector control, published earlier this year:
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
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. …
Africa south of the Sahara, except for South Africa and some of the islands,
was not incorporated into the global malaria eradication campaign of
1955-1969, except for a number of pilot projects aimed at examining the
feasibility of interrupting malaria transmission. Therefore, few of the countries
developed the infrastructure to undertake IRS on a national scale. As a
consequence, most countries have concentrated their malaria control efforts
on the development of primary health care to make appropriate disease
management accessible to the whole population, limiting mosquito control
to urban areas and certain economic development projects.
This situation weighted heavily in favour of ITNs versus IRS as the malaria
vector control measure of choice for tropical Africa. Moreover, the personal
protection afforded by ITNs made it possible to plan its implementation
as a promotional programme aiming at a progressive increase in coverage
before reaching the level of coverage necessary for community protection.
OK, what does the new position paper say? What scientific evidence supports the change of policy?
There is no definitive conclusion on the comparative cost-effectiveness of IRS versus ITNs since it depends on the local context. Thus, countries should maintain IRS in their malaria control strategies, where indicated, until further information, including locally-generated data, is available and can be used to fine-tune national interventions and better guide resource allocation.
In other words, let’s collect the evidence to see if increased use of IRS is a good idea.
Resistance to DDT and pyrethroids in major malaria vectors has been found throughout West and Central Africa, in some areas at a high level, as well as in several parts of Eastern and Southern Africa. …
A comprehensive assessment of resistance at the local level must be carried out before planning any IRS programme, especially in West and Central Africa.
In other words, let’s collect the evidence to see if increased use of IRS is a good idea.
The choice of IRS, or any other vector control intervention, must be made by careful consideration of the factors mentioned above, and will depend on the local context and the strategic objectives, whether elimination of local transmission, transmission control, or personal protection. The role and limitations of existing malaria vector control interventions and personal protection measures
have been reviewed by a WHO Study Group and a comprehensive report recently published (15).
That’s the report above which said that ITNs were the vector control method of choice for tropical Africa.
IRS is indicated only in those settings where it can be implemented effectively, which calls for a high and sustained level of political commitment. Transmission control operations based on IRS, or any other vector control intervention, have to be maintained at high coverage levels for extended periods of time, for as long as impact is needed.
IRS requires effective leadership and management for planning, organization and implementation. Operations must be managed by skilled professional staff, based on an analysis of local epidemiological data and a sound understanding of transmission patterns, vector behaviour and insecticide resistance status. Significant strengthening of human and technical resources, accompanied by sufficient financial resources, is needed to develop or reorganize existing IRS operations.
So, the old policy was that ITNs should be used in areas of stable transmission because there wasn’t the infrastructure to support IRS. And the new policy is that IRS should be used in areas of stable transmission provided that there is sufficient infrastructure. In practice this seems to amount to almost no difference.
John Quiggin comments on this matter:
It’s far from clear that the change is backed up by a scientific analysis of the relative cost-effectiveness of the options. But, as with all the fads and fashions in areas like this, cost-effectiveness is not necessarily the most relevant criterion. The US appears willing to put in a substantial amount of extra money, and the US wants to push DDT. So, it’s probably better to please the donors, than make a stand on the science and risk losing the money.