DDT, Mozzies and Malaria
Threads - An ongoing concern over the years, so this article will summarise pertinent material chronologically.
On 2/9/2002, in the thread Global Summit Resource Request, Peter Macinnis wrote:
I have already retrieved the Rio Declaration and some parts of Agenda
21 -- a huge and sprawling document that sets out to provide a
blueprint for dealing with the world's woes -- find it at
http://www.igc.org/habitat/agenda21/
> I shall open my eyes to see if there is anything interesting for you. Is
> this overview to be presented to non-scientific people, with little
> knowledge of the poor state of Mother Earth?
Assume secondary school level. There are three aspects to environmental
education: knowing, caring and acting. If people achieve any two of
these, the third can be expected to follow. I expect these to be people
who probably care, but are generally unaware of what the real problems
are. So my aim is to see them accurately informed with understandable
material, so they can then explore ways to act.
I am concerned also for activists who care passionately but no little,
and so act wrongly, through lack of proper information; I need to set
out the facts and make them think beyond the normal confines, where
only the Third World has problems.
So I will take Margaret Ruwoldt's piece the other day on why paving the
US is causing water problems, and link that to a number of other
pieces, with cross references to articles over the past five years
saying that 21st century wars will be about potable water (and some
less potable), and some of the stuff that comes out of Johannesburg. If
it gets the nod, I may add Zero's find on water purification, and so it
goes. I will also go back to a story I did on "rain gardens" in April,
which ties in with Margaret's information.
I also need data -- I am old enough to recall when Paul Ehrlich used to
come on lecture tours, and had factoids on filing cards in his shirt
pocket, so he could reel them off. If you know how many people are
dying of malaria because DDT is not used, and how many animals are
being harmed by DDT when it is wisely used, you can make an INFORMED
decision. I need to know the minimum amount of water we need to retain
our lifestyle, and how much an Afghan subsistence farmer needs, and a
Bangladeshi farmer. I need to know what energy level we live at (about
7.7 kilowatts to maintain the WHOLE lifestyle) and what an Iranian
villager lives at (around 1.1 kilowatts).
In "Chemicals of Concern", 6/6/2003, Jim Edwards replied to a post by Toby Fiander:
The two or three sentence summary of the conference attended by
my colleague is simply this. There seems to be some consensus
among Australian researchers that:
... the effect of byproducts of chlorination of water supply is
about ten times as important as any human effect from endocrine
disrupting compounds (EDCs), if indeed there is any effect at
all; study of chlorine byproducts is not as sexy as that of
EDCs; the effect of both appears small,
... there are measurable changes in sex balances in fish and some
other wildlife, which may have some link with EDCs, but we are
still at the stage of gathering data about what the effects are
and what chemicals are likely to contribute to these effects,
... no one has any real idea about what to do about EDCs, because
there is so little data about what the effects are and which
chemicals cause them, but there are viable strategies for
minimising chlorine byproducts, which will probably be adopted in
water supply in the long term,
... not surprisingly, preliminary data shows some of the worst
effects from EDCs appears to be associated with stores of them,
like the waterways near Olympic Park, Homebush Bay - there is a
possibility that the conclusion is related to sampling strategies
(ie. more data gathered where the stuff is in the soil) and this
needs to be investigated.
<snip>
A quote from "Our Stolen Future" by Colborn, Dumanoski and Myers p.253:
"Chemicals known to disrupt the endocrine system include: DDT and its
degradation products, DEHP (di(2-ethylhexyl)phthalate), dicofol, HCB
(hexachlorobenzene), kelthane, kepone, lindane and other
hexachlorocyclohexane congeners, methoxychlor, octachlorostyrene, synthetic
pyrethroids, triazine herbicides, EBDC fungicides, certain PCB congeners,
2,3,7,8-TCDD and other dioxins, 2,3,7,8-TCDF and other furans, cadmium,
lead, mercury, tributyltin and other organo-tin compounds, alkyl phenols
(non-biodegradable detergents and anti-oxidants present in modified
polystyrene and PVCs), styrene dimers and trimers, soy products, and
laboratory animal and pet food products."
This was a footnote to a consensus statement issued by a multidisciplinary
group of experts gathered in a retreat at Wingspread, Racine, Wisconsin,
26-28 July 1991. Participants included experts in the fields of
anthropology, ecology, comparative endocrinology, histopathology,
immunology, mammalogy, medicine, law, psychiatry, psychoneuroendocrinology,
reproductive physiology, toxicology, wildlife management, tumor biology, and
zoology.
Is it just in North America, then, that EDCs have become such a serious
threat to human biology? Or are we in Australia confining our studies to
stormwater and ignoring all other parts of the environment? I would hate to
think that there was some sort of cover-up, but after the Pan scandal one
wonders how far the chemical/pharmaceutical industries can be trusted.
Certainly, the information in the above book seems to give the lie to the
statement:
... no one has any real idea about what to do about EDCs, because
there is so little data about what the effects are and which
chemicals cause them
I know it takes time for information to trickle down to the 'arse-end of the
world', as Keating called it, but surely 12 years is enough time for our
scientists to catch up on what is happening in the rest of the world.
Toby Fiander replied:
The
consensus you quote is not shared by all, or indeed the majority, of
the world's scientists. I have quoted papers previously which are of
recent date, which indicate the situation I have described.
> Is it just in North America, then, that EDCs have become such a serious
> threat to human biology?
The
research canvassed at the recent conference is not just Australian
research. One of the keynote speakers was from the USA, two of the
other papers were about data collected for the world and all papers
referred to the published literature.
The
list of chemicals you provide is the list at which the conference
commenced, and there seems to be little and ambiguous data to support
the idea that there are human effects from these chemicals here or
anywhere else. While it is nice that you enjoyed the book, there are
other points of view and the matter is not settled.
BTW, I don't share Keating's cultural cringe - there is internationally significant work on this matter occurring in Australia.
In the thread "OGTR - Educate, Don't Pontificate", on 28/7/2003, Podargus replied tp Rod Olsen:
> The APINTs have had some bad experiences of science gone wrong during the
> 20th century
>
> - After DDT, Minamata Bay, Bhopal, Love Canal, cane toads, and many other
> environmental disasters, I can well understand the reluctance of many
> non-scientists to embrace genetically-modified crops in agriculture
While DDT has had some problems, it still has a valuable role in controlling malaria, arguably in this case the advantages (now) outweigh the disadvantages. Minnamatta Bay and Bhopal were commercial in their causes and cane toads were introduced against the advice of scientists.
Ray Stephens replied:
While DDT has had some problems, it still has a valuable role in
controlling malaria, arguably in this case the advantages (now) outweigh the
disadvantages.
I didn't know Plasmodium was susceptible to DDT?
-tic
Personally, I
wish that advances in DNA analysis which find that Plasmodium is more
plant than it is animal would come to play in control of the parasite
itself rather than its vector.
Okay, they are
'only mozzies', but using DDT is like trying to kill the messenger, and
using DDT (in spite of human survival in the short term) is setting
loose an interspecies, residual toxin upon the environment, with the
potential to inhibit more than only a blood parasite.
Not good.
Peter Macinnis responded:
Ray,
I'm not sure how much you are joking here, so I shall respond
seriously. Rather more than 40 years ago, I used to see "fogging" in
the streets of Port Moresby, done as a means of mosquito control, with
the known safe substance, DDT. That was a year or so before Rachel
Carson published.
Nobody
wants to use DDT that way any more (I hope), but DDT-impregnated pads
in huts in sub-Saharan Africa can seriously reduce the number of
mosquitoes, and the number of bites by infected mosquitoes, with very
little DDT getting into the environment. This saves lives by preventing
infection while doing minimal harm beyond the hut -- any mosquitoes
that are later eaten will send their DDT into assorted food chains, but
the dose escaping is FAR less than from spraying.
In
the 1960s, I used to sell 24D and 245T in a hardware store -- I was the
official expert, because I could pronounce the names on the labels --
but we all knew 24D and 245T were safe -- they were just plant
hormones, after all . . . nobody told us about traces of dioxin, or
metabolic breakdown products.
As
in so many things, there is no totally safe answer, but a cunning and
informed awareness can save us from the worst excesses when we make a
wrong call. We cannot turn our backs on the risks, but we should not
allow flakes to terrify us of bogey-men to the extent that we fail to
notice the shark behind us.
Bans
are not the way to go, but informed restrictions on use certainly are
-- and in appropriate cases, based on the evidence, the restrictions
may well be indistinguishable from bans, except that they have been
applied with commonsense by people who are informed -- which brings us
back to the highly intelligent subject line.
When challenged by Podargus, Ray responded:
No, not good, but what is your solution?
You're right
Podargus, I'm unable to offer an effective alternative for malaria
control unless PPE (personal protective equipment) can be made into one.
Surely mosquito
proof sleeping netting and possibly a proven effective mosquito
repellent like "Aerogard" provided to people who otherwise couldn't
purchase same, would be better than risking negative interference with
biodiversity?
Then, perhaps DDT is an improvement, all the same, on another technique used which involves reclaiming wetlands?
I'd prefer a broad spectrum Plasmodium killer (or *vaccine*), but such a thing doesn't yet exist.
WHO - Roll Back Malaria by 2010:
http://mosquito.who.int/cgi-bin/rbm/dhome_rbm.jsp?ts=3237069713&service=rbm&com=gen&lang=en
Paul Williams answered:
"The
World Health Organization will announce today in Tanzania that it will
spearhead a program to reduce death from malaria by increasing 30-fold
the use of insecticide-impregnated mosquito nets in Africa."
October. 1999.
http://www.malaria.org/news147.html
Child mortality has been reduced by 25% (and more) in many African countries where this method has been employed.
We
may applaud this effort - or we should.... But... my understanding is
that figures are now demonstrating a orresponding increase in later
onset malaria in the countries trialled. These later onset cases when
the immune system is more mature are much less likely to be directly
fatal.
> Then, perhaps DDT is an improvement, all the same, on another technique used
> which involves reclaiming wetlands?
>
DDT is still used to treat walls and furniture in areas where it is still effective:
http://www.malaria.org/
That it is still used broadly in some places is understandable.
The
low cost of DDT and how we value human life are factors which may test
our grounding in what is terrible reality for many of the world's
peoples.
> I'd prefer a broad spectrum Plasmodium killer (or *vaccine*), but such a
> thing doesn't yet exist.
>
In the thread "Journalism and the promotion of smoking" on 25/10/2003, Jacqui Owens posted:
<snip>
The tobacco
companies have included so many other chemicals (DDT and its
derivatives) and natural products (chocolate) to enhance the taste and
initial addiction so once the child actually gets through the
rebellious stage and wants to give up, it is too late; they are
addicted.
<snip>
Paul Williams responded:
I
don't believe that you really mean that tobacco companies added DDT to
either enhance flavour or increase initial addiction? DDT is still used
in some countries for various insect problems (malaria mosquito larvae
and adults being one of the main targets) DDT may well be used in some
places for tobacco pests - it may also be used to perhaps protect a
crop in storage - I do not know. That it would be added for taste or
addiction reasons appears very doubtful.
I
would be interested in where and when chocolate was added to tobacco
products? It does, on the surface, seem plausible that adding chocolate
could enhance flavour.
Adding
extra nicotine (or developing crops with higher levels of nicotine)
would seem logical to enhance addiction. Sodium nitrate has been added
to cigarettes (to enhance burning? and possibly insect control?)
This resource may be of interest:
http://tobaccodocuments.org/
Positive (sort of) notes:
Nicotine
is not the complete demon it has been made out to be. There is some
evidence that cognitive function can be hightened by controlled
ingestion of nicotine. There is strong evidence to indicate that *abject misery* is experienced
by
many who attempt to give up. This misery is only partly to do with
physical withdrawal - I would say has the sneering attitude of
self-righteous individuals has much to do with this misery.
Those
who are willing to 'cast the first stone' may be creating more misery
than they know. Those who promulgate this 'stone casting' (through
ignorance) into a veritable hail of abuse and who continue to increase
the burden on those who one should care for - and continue to sneer in
their self-opinionated ignorance - have not the wit to develop their
own understanding of what suffering is.
They know not - and demonstrably care not.
Ray Stephens commented:
Considering that
the only other function nicotine has beside that of pandering to
addiction, is as an insecticide, I find the use of DDT with crops a bit
of an overkill.
If the insect bugs are already resistant to nicotine, I doubt it will take long before DDT is mere sugar on their leaf flakes
On 18/12/2003, in the thread "Michael Crighton and Environmentalism", Paul Williams wrote:
> http://www.crichton-official.com/speeches/speeches_quote05.html
>
> This appears to be genuine -- it is certainly thought-provoking
>
It is genuine.
Crichton's speech reflects many of my own thoughts.
(This is a danger - so it is therefore best to criticise what I can).
Umm... There is some evidence that DDT and it's breakdown products may have an effect on the eggs of birds:
http://ehpnet1.niehs.nih.gov/docs/1995/Suppl-7/fry.html
Nevertheless;
I support DDT use - particularly for malaria vectors. Millions die every year from this disease.
There has been much harm caused by ignorance and belief masquerading as science.
I'm sick of the crap.
I would actually prefer to answer others' criticisms for I think that
he's basically dead right...
Peter Macinnis replied:
My own take is that he is a bit of a curate's egg. A thin-shelled one, perhaps from DDT? Crichton says:
*>I can tell you that DDT is not a carcinogen and did
*>not cause birds to die and should never have been
*>banned. I can tell you that the people who banned it
*>knew that it wasn't carcinogenic and banned it anyway.
DDT was targeted
because it was accumulating in the environment, it caused bird shells
to become thin, and it is a possible carcinogen in animals. He is wrong
to the very edge of lying.
It has not been
entirely banned, and just as well. It should not be banned. He is
right. Some of the evidence led against DDT was a bit didgy. He is
right again.
The middle
ground is that DDT needs to be restricted in its use -- he fudged on
that, because he is NOT intellectually honest, he is arguing a
particular corner.
Any smarty-pants
can come along now with the benefit of 20-20 hindsight and squillions
of Hollywood dollars for making up stories where scientists all do evil
and wrong things (unlike certain
ex-medicos-turned-film-and-pulp-fiction-writers), and point to errors
in projections made on the best evidence available. I used to go and
listen to Ehrlich -- he always made it clear that the dooms he listed
were what we faced if nothing improved.
Things improved:
so what? There are still potential disasters ahead. We don't say the
scientists are/were idiots, we feel grateful for an escape, look to see
where the next blow is coming from, and we duck that as well.
Crichton gives
comfort to the people who believe God is there to make sure their
profit line is never dented. He supports the enemies of humanity with
glib glossing. He assures them their opponents are all fluff and
nonsense, and so must be wrong.
On the other
hand, the best friends the enemies of humanity have are the eco-fundies
with their craziness. The eco-fundies desperately need educating, so
they can say with precision what is wrong, both with the environment
and with Crichton's claims. Instead, they retreat into argumentative
duplicity that would come better from a creationist, a homeopath or a squarer of circles. In that, annoyingly, I believe Crichton is right.
Tamara Kelly added:
Also - in the long run - DDT is not the answer. At least by banning it we
looked for other methods of pest control and possibly pushed biological
control along the track a bit quicker.
Peter Macinnis responded:
Chris Lawson dealt with this rather well in his frankenblog -- see http://members.ozemail.com.au/~claw/frankenarchive001.htm and search on DDT
In the long run,
true -- but in the short run, limited and controlled use of DDT does
the least damage. It saves many lives and has extremely limited release
of DDT and DDE.
As a rule,
resistant organisms are less "fit" when the environment is free of what
they resist (in at least one case in E. coli, antibiotic resistance is
retained even when the antibiotic isn't around, but generally the rule
holds). So if DDT use is limited, evolved resistance does not gain an
overall advantage -- but if we are going to phase out DDT (as we must,
in the long run), it DOES NOT MATTER if insects become resistant. What
matters is that we can reduce the incidence of malaria.
Tamara Kelly answered:
OH! Thanks for that. You have just helped me along with figuring out the
pros and cons of organic farming.
Announcement: I'm off to play farmer next month. We've just bought a hobby
farm west of Gin Gin - 30 acres & 900 olive trees
frogs, dams, creek, cows (read: meat), etc...
AND a friend has already asked me to run a few projects:
The Coxen's Fig Parrot has been sighted at Gin Gin and Parks & Wildlife
want someone to hunt it down and confirm it. Fun Fun Fun!!!
The effect of planting native olive species close to exotic olive species
to take advantage of existing olive predators.
The use of lomandra around the base of trees for a living mulch and
nutritional shedding. This one I am a little skeptical as the area is
stoney with a clay base and too much water will bugger the olives so I am a
little dubious as to the potential success of this one. There seem to be
many types so I suppose I'll eventually find one that's appropriate. Also
harvesting will be a bugger if there's bloody great rushes underneath!
Paul Williams noted:
> Hi Paul, all
> Wasn't one of the reasons that DDT was banned, because insects became
> resistant to it? So
> heavier doses would have only succeeded in poisoning the environment?
Peter touches upon this in another post.
Broadcast spraying of the environment is no longer recommended.
DDT is mainly used inside houses
DDT is the only
affordable way for poorer nations to reduce the estimated 500 million
malaria infections leading to 2,500,000 deaths worldwide each year.
Poor countries such as Guyana have had over a 10 fold increase in malaria infections when DDT spraying has been reduced.
There is no affordable alternative for poorer nations.
Hopefully one day there may be.
If we used just one percent of the money spent on defence worldwide....
Jim Edwards commented:
I noticed that he is fond of the phrase "I can tell you . . .", which
suggests to me that he is aware that what he can tell is probably not true
but by putting it that way he suggests that he is letting you into a secret
so you will think it must be true.
He may be right that DDT does not directly cause cancer although its
breakdown product DDE may do. The reason Rachel Carson focussed on cancer
in her book, "Silent Spring", was because she herself was suffering breast
cancer. She did not, however, ignore the endocrine disruptive effects of
DDT, the early pages of her book describe farms where the hens brooded but
no eggs hatched, where pig litters were small and the young only survived a
few days. It is this effect on hormones of DDT and other synthetic
chemicals, known since the studies of Burlington and Lindeman in 1950, that
is the real reason why they should be severely restricted in their use, but
it was not until 1972 that anything was done about it, and then only because
Carson made the cancer connection.
"I can tell you that a blue-ribbon panel in Science magazine concluded that
there is no known technology that will enable us to halt the rise of carbon
dioxide in the 21st century. Not wind, not solar, not even nuclear
[fission]. The panel concluded a totally new technology - like nuclear
fusion - was necessary, otherwise nothing could be done and in the meantime
all efforts would be a waste of time."
How the hot fusion brigade must have loved that bit! Having destroyed any
chance of cold fusion getting off the ground, they now had the backing to
kill off all other non-carboniferous energy technologies. Likewise the oil
and coal industries could take heart from: "I can tell you that the evidence
for global warming is far weaker than its proponents would ever admit."
Shades of Lomborg! We can have our cake and eat it, we can't stop the rise
of carbon dioxide but it doesn't matter because it won't cause global
warming anyway, so there!
and:
If we could find a way to kill the parasite directly we would not need to
use DDT to kill the vector. It looks as though research is getting closer to
that goal:
http://www.findarticles.com/cf_dls/m1200/10_156/55982943/p1/article.jhtml
Peter Macinnis disagreed:
But that was
1999, and nothing has really happend -- I am afraid there is a parallel
with this comment from Sir John Cockcroft on fusion power in 1957,
quoted by Egon Larsen, Atomic Energy, Pan Books, 1958, p. 161:
We are now at
the same stage as fission research was in 1940 when the possibility of
a chain reaction was well understood but many uncertainties remained,
and a further fifteen years elapsed before large-scale nuclear
power was developed.
That is as true now as it was then :-)
The problem is that malaria keeps getting away as well.
In the thread "Health Threats" on 25/5/2004, Janet Comyn wrote:
I have to agree with Paul on the threat of Malaria globally. I fear,
though, that it may be too late for careful use of DDT to control the spread
of this disease, as our past extravagant use has rendered many target
species resistant.
Paul Williams answered:
There may well be some malaria vectors immune to DDT.
In most countries where malaria is a huge problem this is not the case though.
DDT is generally very safe for humans, including young humans.
We could save millions of lives if DDT was not (now) so demonised.
There are environmental groups who use their power (money and influence) to stop DDT being used for any reason.
I would suggest to them that they take themselves and their children to live in places where malaria in endemic.
I wonder if when their children died from malaria (as some would), they would change their (indoctrinated) beliefs at all?
On in the thread "Malaria Revisited", Peter Macinnis wrote:
G'day from the other side of Brookvale -- seems like the rest of the
world is still asleep.
The strain is falciparum -- more deadly than vivax. See the
backgrounder below, now 30 months old. The usual caveat about mark-up
codes applies.
peter
----- Original Message -----
From: "Meredith" <info@soundwarp.com.au>
To: <SCIENCE-MATTERS@YOUR.ABC.NET.AU>
Sent: Friday, August 20, 2004 7:48 AM
Subject: Malaria revisited
> Hi all,
>
> We discussed malaria some time back. Does anyone know much about the
> strain "falcipirum"?
Malaria backgrounder
(February 2002)
The February 7 issue of Nature offers a series of review articles on malaria. While this disease was eliminated from northern Australia, the United States and most of Europe in the first half of the 20th century, this came from changes in agriculture and land use, changes in housing construction, and in some cases, 'targeted vector control', where the mosquitoes that spread the disease were attacked. There has yet to be an effective sustained attack on the different malarial parasites.
The parasites have a number of different life stages, and no one treatment will attack all of them, which means that some stages of the life cycle are likely to survive, and then push on, causing reinfection. As well, the parasites show a remarkable ability to develop resistance to the various anti-malarial drugs.
The 1950s and 1960s saw effective control programs started in India, Sri Lanka and the (then) USSR, using DDT sprays to control mosquitoes, but the cost, public resistance to spraying programs, and the development of DDT resistance by the mosquitoes saw the programs fail. It may seem odd that people would oppose such a program, but it was carried out mainly by 'fogging trucks' which sent out a dense mist into trees and houses on either side of the road, spreading DDT across the environment but still missing many mosquitoes.
There was very little spraying done in sub-Saharan Africa, where DDT is now used in a sensible way, impregnated into cloth hangings and bednets where mosquitoes can land and rest - and die. This does not spread DDT, but targets the problem species only. Malaria remains a serious problem in sub-Saharan Africa, and in South America and parts of Asia.
The problem is most intense in sub-Saharan Africa, where the main vector is Anopheles gambiae, a mosquito which prefers to bite humans - in medical-speak, it 'preys preferentially' on humans. Anopheles gambiae is also long-lived, giving it more chances to pick up the parasite, and then spread it.
In technical terms, the mosquito has a high entomological inoculation rate, or EIR. This is the standard measure of the frequency with which a single person is bitten by an infected mosquito in a year. In Asia and South America, EIR rates of about 5 are common, but EIRs of more than 1000 have been encountered in sub-Saharan Africa.
A number of factors are contributing to the looming malaria crisis. In some parts of South-east Asia, there are now strains of Plasmodium falciparum that resist almost all of the standard antimalarial drugs, while strains of the less deadly Plasmodium vivax that are resistant to chloroquine are now emerging. There is increasing resistance of the mosquitoes to insecticides in sub-Saharan Africa, which is hardly surprising, given that catches of 200 or more mosquitoes in a single room, with between 15% and 5% of them infected, are common.
African wars have led to more people being exposed for longer, increasing the infective base in the population, while climatic changes may, or may not be playing a role. It is clear that floods driven by El Niño are a cause of increased mosquito populations. The other main factor, of course, is population increase. The rate of infection increases as a power factor of the population, because mosquitoes find it easier to find an infected person to bite, and then later, to find an uninfected person. As well, a greater population leads to more warfare and unrest, and causes infected people to travel into uninfected areas, and people with no infection to travel into infected areas. Tourism is also playing a part, with about 7000 imported cases of malaria being seen in Europe each year.
(It is worth noting here that a report in the February 21 issue of Nature indicates that over two decades at four high-altitude sites in East Africa, there have been increases in the levels of Plasmodium falciparum infection, yet over the past century, climate changes that might favor the transmission of the parasite simply have not happened.)
Malaria is a disease of poor countries, and may even be partly responsible for the poverty that they suffer. In 1995, the per capita gross domestic product in malarious countries was estimated at US$1526, while in countries without intensive malaria, the per capita GDP was US$8268, more than five times as high.
The economic effects of malaria bite deep. Young children are the main victims, with more than 2000 dying from malaria each day, around the world, one every 40 seconds, but even the survivors suffer as they miss school and vital education. More time may be lost from school when older children need to stay home to care for other sick family members, while a sick adult is not earning income for the family, which may not feed, and so become sick as a result of malnutrition. The survivors often suffer from damage which may loosely be lumped together as impaired thinking ability.
Then again, pregnant women who suffer from malaria are more likely to produce children with a low birth weight, and such babies are two to four times more likely to fail to succeed in school. The poverty of malarial countries has an even more profound effect: since the people of those countries cannot afford to pay for expensive drugs, vaccines and other treatments, there is little point in investing the billions of dollars that would be needed to defeat malaria, as investors would get no return on their money. Pharmaceutical companies are not entirely flint-hearted, and some work is going ahead, but there is far less work on malarial treatments than there is on the diseases of the rich - if there were, the shareholders would be rightly annoyed.
Perhaps the answer is already there. A Chinese herbal medicine, qinghao (Artemisia annua), contains a substance called
artemisinin, and this has been used in the past for treating fevers. This is now under intensive study (see Antimalarial drug passes animal tests, August 2001). The main interest is in three derivatives called aremether, arteether and artesunate, all of which are metabolized to dihydroartemisinin. It is this useful chemical that attacks the sexual stage of the parasite, the gametocytes, which are also the stage that infects a biting mosquito.
There is good potential here, and artesunate is already being used, along with mefloquine in some parts of Thailand, but these drugs are currently more expensive than treatments like chloroquine, so once again, we are back at the poverty problem.
The malarial vaccine that has been 'just around the corner' for decades is still just around the corner. The problem is that a person with a fully functioning immune system and prior experience of malaria can still be fully infected, where a single dose of many other diseases confers life-long immunity. Then again, the vaccine that acts to make the body attack certain stages of the life cycle will have no effect against other stages. There are estimated to be somewhere between 5000 and 6000 malarial surface proteins, which makes choosing a potential target even harder.
Still, there have been trials where mosquitoes with irradiated malarial sporozoites (the stage that infects humans) have been allowed to bite rodents, monkeys and humans, and these treatments seem to give protection to about 90% of all those involved. People who have been repeatedly infected develop 'naturally acquired immunity' (NAI), which gives them some degree of protection against the clinical disease we call malaria, but they still carry the parasites, and if these parasites are eliminated, the people can then be reinfected.
The answer may lie in genomics: we now have the human and mouse genomes, we have useful information on the Plasmodium falciparum and P. vivax genomes, while the rodent malarial parasites P. yoelii, P. chabaudi and P. berghei, are all under study, as is the monkey malarial parasite P. knowlesi. Added to this, work is progressing on the Anopheles gambiae genome, and curiously enough, the work on the Drosophila melanogaster genome.
You will find some of the background for this in Fruit fly model: how mosquitoes carry malaria, June 2000, but in the roughly 200 million years since the mosquitoes and the fruit flies diverged, very large parts of the genome have been conserved, even whole chromosome 'arms' seem to have been conserved. That means that the differences between the two types of fly must be lumped together, and that includes the genes for blood feeding and the genes for tolerance of the parasites - keep in mind that the parasites also get sick from malaria, but less so than us, because they have had longer to get used to the infection.
Now imagine a situation where we can identify a gene for tolerance to the parasites. If we can somehow destroy that gene in mosquitoes, when they get a dose of malaria, they die. Or perhaps we can develop a double-ended molecule, with one end locking onto the parasite while the other end acts like a beacon to attract the attention of the immune system.
The only way to determine the future with any certainty is to shape it. We cannot predict what may happen in the next twenty years, but some of the opportunities that are opening up look very promising indeed.
Key names: (climate change in East Africa story from Nature, February 21) Simon Hay, Jonathan Cox, David Rogers and others.
The source: the usual reliable Australian encyclopaedia.
In the thread "GE Cellulose" on 5/7/2006, Toby Fiander posted:
Can I have a reference for the incident you have outlined, please, Michael?
I am not doubting your story, but I would like to examine the context.
On the whole, the idea about regulation is so that exactly the sort of
testing referred to is obliged to be carried out prior to obtaining approval
for use/release. Regulation of accidental escapes ought to be commensurate
with the risks and potential consequences of escape.
When a couple of us wrote to the OGTR a few years ago, our correspondence
was treated poorly. We did not obtain an answer within a satisfactory
timeframe and it required some quasi-political intervention to get what was
a rather condescending reply ignoring some of the central points of the
inquiry. It was concerning that the OGTR did not see its role as broadly as
we thought it ought to and that concerned and educated members of the public
were treated so poorly - we were, after all, likely to be among the greatest
defenders of the regulatory regime!
Until there is a low-cost and ubiquitous treatment for malaria, it is a bit
silly to condemn the manufacture DDT from the comfort of the study in a
place with lots of hospitals, however poorly run.
Michael Bailes replied:
For details of the soil bacteria involved see David Suzuki and Holy
Dressel's "Naked Ape to Super Species" A & U 2002.
Their are alternatives to DDT that don't have half-lives of 18 years,
accumulate in the food chain and in the fat of mammals.
I have written to WHO asking them not to used DDT in mosquito
prevention programmes and suggesting other alternatives.
I think mosquito attractants, as yet untried on a large scale, are one
of the ways to to go. There are some simple tecnologies and the high
tech ones need more research to make them affordable
Toby Fiander answered:
Yes, all good... but until there are alternatives, getting rid of DDT is
problematic. WHO has experimented with a bunch of other things, as I
understand it. I am off to a meeting (GHU) but I will have a look tonight
to see if there are details. You may already know, Michael.
Gerald Cairns commented:
I
have commented before that using insecticides is another selection
pressure for resistance that in many instances we could do without. I
offer a purely anecdotal report of what we do here. This philosophy
also extends to bacteria etc. where it is appropriate.
Rather
than use insecticides to control mosquitos here contrary to the
official wisdom we deliberately allow containers to stand part full and
the mosquitos to lay their eggs then tip them out periodically. This
could be simply mechanised and this avoids forgetting to empty the
tubs. My theory is that each female probably lays only a single batch
or perhaps two before dying. This technique means that these mossies
have wasted their efforts and do not lay their eggs elsewhere. The
technique seems to work because we have very few mossies around the
house but it is strange that there are lots of them in the bush about
2-300 m away yet they don't seem to migrate much which is surprising.
Of course this may not apply to all species and wind dispersion is
probably also a factor.
Nikki Sutton said:
Thanks for your simple tip we are currently inundated with moozzies at the moment so i am going to try your method.
On 5/7/2006, in the thread "Mosquito - Repellant Eucalypts ", Geoff Pain wrote:
Oil from some eucalypts, especially E. Citriodora or Lemon-scented gum is recognized by US Govt agencies as mosquito repellent and even planting near homes helps.
As effective as DEET. A number of commercial preparations are available.
I am currently reviewing applications of eucalyptus oils, mainly the cineole types with a view to mass production in WA.
Grateful for any application info.
You might not know China dominates the eucalyptus oil market and Australia imports the stuff!
Ella Boyen noted:
Ok so I haven't
read the previous posts but in terms of insect repellent Desert
Dwellers (Alice Springs) and Ayers Rock Resort sell an insect repellent
that is made from sandalwood and ... rose oil...? It smells like Vicks
Vapour Rub and is very effective.
Michael Bailes wrote:
Look this was just an aside to another post but the problem is the malaria
mosquito.
The UN has finally got a Top Gun to do something about it. (It is probably
the number 1 health problem of humans on this planet - and probably has been
for thousands of years).
The Top Gun has decided to use DDT probably because it is so persistent and
gives long lasting protection. You can't repel mosquitoes in tropical areas
where you can't see blue sky for them.
I have a big problem with DDT and all the chlorinated hydrocarbons. Apart
from their tetrogenic effects they persist in the world's ecosystem for
generations. They may even interfere with the maternal response of mammals
like seals.
Just google mosquitoes, UN, and DDT and many sites appear eg
http://news.bbc.co.uk/2/hi/africa/4264374.stm
There has to be a better way to go!
Many African nations can grow pyrethrium daisy which, while you may need to
spray more often, is not as toxic to the planet.
They can also grow the new anti-maleria herb/drug Artemesia annua ( a
variety of Wormwood)
This is the text of the message I sent to the UN Top Gun ( I have forgotten
his name sorry - fascinating , uncompromising, semi -retired, Japanese,
golf-playing, doc). I encourage others to write to the UN questioning this
environmentally disastrous policy
"Please do not use DDT against mosquitoes. Please read 'Silent Spring' and
'Since Silent Spring' for my reasons
There are other alternatives. Pyrethrums for example.
Also we need to develop a cheap mosquito ATTRACTANT.
If we can attract just mosquitoes (we need to leave other insects alone)
we can kill them.
I have seen a low tech attractant made from yeast and two soda bottles.( a
Japanese invention!)
Can you teach local herbalists how to grow and administer Artemesia Anua
"Sweet Annie"?
This may be unpopular with the drug companies but may make the drug more
available.
Harvard Uni has been trialing away of educating native healers in S.
America. (See "Shaman's Apprentice"
Thankyou for you time and good luck with your most important work.
Toby Fiander replied:
Yeah, everyone has a problem with DDT. But it's effective and above all it
is cheap. And if there is to be a trade off between egg shells and human
babies, then the humans win. It does not mean that nothing gets done in the
long term, but it does mean that some baby humans who might have died of
cerebral malaria are still alive. Most people think that is an appropriate
priority.
I have seen children sick with malaria, whooping cough, gut problems - you
name it. I was present when one died of a preventable disease. In a
western context it was treatable. I cannot recount these stories without
tears, and it was decades ago.
The idea is to do something effective and cheap that gets rid of the malaria
mosquito, not to experiment with children.
My grandfather was in charge of DDT spraying for the army at some of the
country bases during WWII. He said washing in it was rather irritating -
perhaps it is not a wheat allergy, Michael.....
Isn't the term, teratogenic?
Michael Bailes retorted:
Toby
You do nurse a grudge don't you?
The" :)" was meant as a peace offering
Pardon my spelling of tetrogenic. Spelling is not my forte
Genetic abnormality is horrible
DDT is shit it should not be allowed on the planet at anytime, anywhere, for
any reason
I have worked in a ward of tetrogenic children. I have seen the heartache
and guilt of parents who had their house sprayed with DDT while they were
pregnant
Have you?
Toby Fiander answered:
Michael went on:
I have worked in a ward of tetrogenic children. I have seen the heartache
and guilt of parents who had their house sprayed with DDT while they were
pregnant
I have worked with the poor in a couple of countries, homeless blokes,
homeless women running away from blokes, various kinds of people who might
be called insane and the aged. I have done a range of things, but I have
never worked with those who have a congenital deformity, although I did once
work with... no never mind.
I think you should be careful about ascribing the deformities to exposure to
DDT or even a group of chemicals. Guilt is probably unfounded.
DDT is shit it should not be allowed on the planet at anytime, anywhere,
for
any reason
That is quite blinkered given the sort of devastation that will be caused by
withdrawing it completely and suddenly.
I appear to have replied to your offlist email and sent it to the list, for
which I apologise to the list.
You do nurse a grudge don't you?
Eh? Is there some internal process you want to tell us about?
I don't like bad science, data-free zones and a bunch of other things to do
with science.
John Winckle observed:
I
have been told that the Chinese 'eucalyptus oil starts life as camphor
oil and is then modified to a good copy of eucalyptus. Where would the
Chinese get lots of gum leaves??
Toby Fiander answered:
I have seen what looked to me like eucalypts in southern China, which is the
only bit I have seen. Also, Country Hour did a bit of feature on them last
year. Have a look here for the summary:
http://www.abc.net.au/rural/nt/stories/s1299302.htm
I have not followed the link any further.
Conversion of one oil to another is still possible - this is China we are
talking about.
On 18/9/2006, Paul Williams wrote:
Good news on malaria - official recommendations are now finally being based
on science and data -not ignorance and hysteria. And, importantly, realistic
funding for the fight against malaria is now being made available.
"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."
- Tom Coburn
15 SEPTEMBER 2006 | WASHINGTON, D.C.
'WHO gives indoor use of DDT a clean bill of health for controlling malaria'
-- "Nearly thirty years after phasing out the widespread use of indoor
spraying with DDT and other insecticides to control malaria, the World
Health Organization (WHO) today announced that this intervention will once
again play a major role in its efforts to fight the disease. WHO is now
recommending the use of indoor residual spraying (IRS) not only in epidemic
areas but also in areas with constant and high malaria transmission,
including throughout Africa."
ACTs - artemisinin-based combination therapies (Jan 2006):
"The inappropriate use of antimalarial drugs during the past century has
contributed to the current situation: antimalarial drugs were deployed on a
large scale, always as monotherapies, introduced in sequence, and were
generally poorly managed in that their use was continued despite
unacceptably high levels of resistance."
------------------------------------
"As a response to increasing levels of resistance to antimalarial medicines,
WHO recommends that all countries experiencing resistance to conventional
monotherapies, such as chloroquine, amodiaquine or
sulfadoxine-pyrimethamine, should use combination therapies, preferably
those containing artemisinin derivatives (ACTs - artemisinin-based
combination therapies) for falciparum malaria."
http://www.rbm.who.int/cmc_upload/0/000/015/364/RBMInfosheet_9.htm
and:
Forgot to give the link:
'WHO gives indoor use of DDT a clean bill of health for controlling malaria'
http://www.who.int/mediacentre/news/releases/2006/pr50/en/index.html
Or:
http://tinyurl.com/e77ud
