Malaria and global warming – no linkage

From World Climate Report: Malaria Declines Despite Local Warming

“Spreading tropical disease” is high on the list of bad things that are going to happen as the world warms—if you believe the doomsayers. And topping their list of spreading tropical diseases is malaria.

But, as we have on many past occasions pointed out, malaria is neither “tropical” nor is it “spreading.”

In fact, back in the late 19th century, malaria was thought to be endemic in most regions east of the Rocky Mountains—brought to the U.S. in the 16th and 17th century by European colonists and African slaves and spreading across the country with the migration of those populations (Zucker, 1996).


Figure 1. Region of the U.S. where malaria was thought to be endemic in 1882 (source: Zucher, 1996).

Malaria transmission was still a problem in some parts of the U.S. into the mid-20th century, and, in 1946, when the CDC was established (back then it was known as the Communicable Disease Center) its primary goal was to eradicate malaria from the U.S.—which it successful achieved within a few years (with the help of DDT).

All the while, the average temperature in the U.S. was on the rise, increasing by some 1 to 2 degrees between 1882 and the early 1950s.

Clearly, a warming climate did not leading to an expansion of malaria in the U.S.

Nor does it appear to be doing so elsewhere.

About 10 years ago, a paper by Simon Hay and colleagues was published in Nature magazine that made this abundantly clear. Hay et al. analyzed the occurrence of malaria in the east Africa highlands and found the number of cases to be expanding rapidly, however, and here is the kicker, try as they might, they could find no evidence of a driver in the form of climate change. They concluded:

The absence of long- and short-term change in the climate variables and the duration of [malaria transmission] suitability at these highland sites are not consistent with the simplistic notion that recent malaria resurgences in these areas are caused by rising temperatures.

That would seem to throw some cold water on the heated rhetoric of the global warming/tropical disease crowd.

But wait. Within a few months time, Nature published a comment by noted global warming/tropical disease advocate Jonathan Patz and colleagues who challenged Hay’s conclusions—not about the increase of malaria occurrence (of course), but that the climate in the African highlands had not changed to become more suitable for malaria transmission. Patz et al.’s basic contention was that:

• The Hay et al. weather data were interpolated over mountainous terrain.

• Because of mosquitoes’ response to climate thresholds, you don’t need a significant trend in climate—climate variability is important, too;

•Nevertheless, based on a different analysis, regional warming trends do exist that match the increase in malaria.

And of course, the press loved this take, for now everything was right again in the world of global warming doom-and-gloom. For example, Reuters reporter Patricia Reaney wrote:

Climate change could be causing more than higher temperatures—it may also be helping to fuel a rise in Malaria in East Africa…Earlier research had suggested the upsurge was due to drug resistance and population growth, and not global warming. But scientists in the United States and Britain say it may not be just a coincidence that the rise in malaria parallels East African warming trends.

So take that, you naysayers.

At the time, Hay et al. answered their critics, and continued to stand by their conclusions writing in response to Patz et al.:

“Evidence against the epidemiological significance of climate change in the recent malaria resurgences in Africa is mounting and remains unmatched by any contrary evidence.”

Now forward the clock to the present day.

Several members of the original team gathered by Simon Hay have gotten back together to see how malaria and climate have evolved in East Africa over the intervening 10 years since their Nature publication. Their results have just been published in the scientific (open access) journal PLoS ONE. The lead author of the new study is David Stern from the Crawford School of Economics and Government, Australian National University.

What Stern et al. found was quite interesting. With 10 more years of climate data, they have identified significant increases in the temperature throughout their study region. Stern explains that “We conclude that there is now clear evidence of increased temperatures in highland East Africa especially in the last 15 years.”

So perhaps their critics were correct all along, the climate has indeed been warming in East Africa concomitant with the spread of malaria?

Not so fast.

It turns out, that over the past decade or so, the occurrence of malaria in the region has plummeted!

That’s right, despite rising temperature, malaria cases have bottomed out to historically low levels.

Stern postulates that the rise in malaria cases in the region during the 1990s “was probably due to resistance to chloroquine, an older antimalarial drug, and not climate change.”

And the decline in malaria cases in the face of rising temperature is further proof that climate change is not a major player in the rates of malaria transmission in the region. No greenhouse-gases-fuelled apocalypse here. Time to turn your attention elsewhere.

But before leaving, Stern gets in a parting shot.

This screenshot below is taken from Stern’s weblog posting on September 17, 2011 in which he seems to give some advice to the IPCC.

Nice idea, but call us cynical as we seriously doubt that we’ll be seeing this “iconic” figure in the IPCC’s next Assessment Report (AR5)!

References:

Hay, S.I., et al., 2002. Climate change and the resurgence of malaria in the East African highlands, Nature, 415, 905–909.

Hay, S.I., et al., 2002. Hay et al. reply, Nature, 420, 628.

Patz, J.S., et al., 2002. Regional warming and malaria resurgence, Nature, 420, 627–628.

Stern, D., et al., 2011. Temperature and malaria trends in Highlands East Africa. PLoS ONE, 6, e24524.

Zucker, J.R., 1996. Changing patterns of autochthonous malaria transmission in the United States: A review of recent outbreaks. Emerging Infectious Diseases, 2, 37-43.

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Related, from Marin County Mosquito Control District

39 thoughts on “Malaria and global warming – no linkage

  1. If mosquitoes depended on warmth, then Alaska wouldn’t be famous for its giant mosquitos.

    If mosquitoes depended on warmth, then malaria would have been familiarly known as Swanee Fever instead of Maumee Fever.

    Scientists should be required to look up basic general knowledge before starting any project.

  2. Malaria is a public health problem, not a temperature problem. Anyway, as anybody knows, one of the biggest malaria epidemics happened in Siberia. The key notion is that it’s so much more convenient to save on public health measures, blame it on global warming and get money from carbon taxes.

  3. Keelings group have just revised the annual level of photosynthesis:-

    “Our analysis suggests that current estimates of global gross primary production, of 120 petagrams of carbon per year, may be too low, and that a best guess of 150–175 petagrams of carbon per year better reflects the observed rapid cycling of CO2. Although still tentative, such a revision would present a new benchmark by which to evaluate global biospheric carbon cycling models.:

    The box diagrams used by the climate modelers have underestimated the biotic sequestration rate by 30%.

    http://www.sciencedaily.com/releases/2011/09/110928222003.htm

    http://www.nature.com/nature/journal/v477/n7366/full/nature10421.html

    This actually means that at least more than 40 petagrams of carbon fall as organic ‘snow’ in the oceans than was initially estimated.

  4. Lots of factors effect where and what species of malaria can survive. In general the most virulent (P.falciparum) must spend part of its life cycle in the mid-gut of the Anopheles mosquito. As temperature declines the time it must spend in the mid-gut increases. The mosquito has a limited lifespan and by the time the temperature declines to about 20C the malaria parasite needs a longer period of time in the mid-gut of mosquito than the mosquito will live. In cold climates where malaria used to be endemic it was because mosquitos were finding shelter in heated man-made structures and/or the parasites were being reintroduced every year by infected humans travelling from tropics to temperate regions.

  5. Malaria in Africa was practically extinct before the banning of DDT. Now, according to the latest charity sob-story to drop through my letterbox, one african child dies every 68 seconds of the disease. Yet another unforseen consequence to lay at the feet of hippy do-gooders.
    There are less than 90 days to go before the 4.5 billion dead from global warming prophecy is due to mature. Maybe someone is getting desperate?

  6. Malaria and global warming – no linkage
    Posted on October 4, 2011 by Anthony Watts

    …..Time to turn your attention elsewhere…..

    Is the siting of temperature devices alongside (or useful for) development projects with lack of consideration for long-term infrastructure maintenance $ and associated tradespeople for the health clinics, sanitation blocks aligned to primary school education facilities, personal hygeine push eg household showers and laundries etc, a cause in the initial rise of mosquito breeding and bearing/malaria?

    My experience from central Australia in the 1980s was when people left the main regional/community hubs to live on tiny outstations all of the above and sewerage systems were later installed under ‘development agendas’. The problem whereby tractors were driven over the septic tanks and or household plumbing and left broken to the atmosphere seemed to correlate with a rise in mosquitoes (and large numbers of mosquitoes, not malarial bearing) experienced for the very first time.
    Gross bacterial skin infections associated with bites/scratching with unwashed hands and general housing environments [and Dengue Fever] was a severe problem, and required intramuscular penicillin or regimes of oral antibiotics.

    And including the effort to revegetate, planting ‘native’ trees and shrubs to combat the ever expanding dust bowls created by the harvesting of fuel (wood) for traditional cooking fires and tribal artefact manufacturing. The water supplies and polypipes were always damaged in an effort by kids to attract small birds for sling-shot practices. Ensuring abundant stagnant pools of water and damp areas that were continually supplied with water and infrastructure was a given under this ‘development’ agenda.

  7. polistra says:
    October 4, 2011 at 4:17 am

    “If mosquitoes depended on warmth, then Alaska wouldn’t be famous for its giant mosquitos.”

    It’s not the mosquito that depends on the warmth. It’s the portion of the malaria parasite’s life cycle that must be spent in the gut of the mosquito – typically 5-10 days for P.falciparum. The parasite can’t survive in the gut of a mosquito that’s gone dormant due to low temperature.

    The malaria parasite is probably the most widely studied organism other than humans. It’s an interesting study in the limits of evolution by natural selection because, you see, there are more individual malaria parasites that live and die every single year than all the reptiles and mammals that ever lived. In all that vast opportunity for malaria to “evolve” solutions to selection pressures it has never found a way to digest the blood of humans with sickle-cell anemia and it has never found a way to survive in the gut of a cold mosquito. The length of time it takes to evolve resistance to man-made anti-malarial drugs is also illustrative. Resistance to a drug that requires a single point genetic mutation happens several times in each infected human. There are about 1 trillion of the parasites reproduced in each infected human. Resistance that requires two single point mutations takes about year and those requiring three take decades. So in all that huge opportunity (trillions of trillions of these parasites have lived and died in recent decades) the parasite hasn’t “evolved” anything new except some trivial genetic changes that give resistance to anti-malarial drugs. And even in the drug resistance cases those mutations quickly disappear as soon as the drug is no longer being used becausae the resistance comes at a cost and when there’s no reason to pay the cost those parasites with the mutation are at a competitive disadvantage with those that don’t carry it. In the meantime, with fewer reproductive opportunities for heritable genetic mutation to occur, reptiles evolved into mammals. One might reasonably ask if trillions of trillions of malaria parasites can’t evolve a way to survive in the gut of a dormant mosquito how a far smaller number of reptiles evolved all the things that differentiate reptiles from mammals.

  8. I seem to recall David Hackett Fischer indicating that Samuel de Champlain recorded malaria type illnesses among the Indians in New France in the very early 17th Century.

  9. With modern technology and facilities we shouldn’t doubt this fact anymore plus we have to understand that although it is a deadly disease, it hasn’t been in the top list of illnesses that are killing people but more modern ones such as cancer and aids.

  10. Only in climate science is speculation elevated to the truth. Yet another over-the-top climate scare bites the dust.

  11. How will Michael Mann explain his payola grant of $1.8 million to study mosquito vectors now?

    Oh, wait. Mann never explains anything. He just keeps saying he was “exonerated.” As if. Still, I’d like to know why that loot didn’t go to a legitimate biologist or epidemiologist, instead of a known charlatan.

  12. From scientific process point of view I can’t see that the above eliminates the hypothesis that malaria is spread more at higher temperature but only shows how efficient DDT and other present means to fight malaria are.

  13. Simples.

    If malaria goes down as temperature goes up, then lack of malaria must be causing the temperature rise (Climatology 1st Law – correlation = causation).

    It is imperative therefore the we severely increase the incidence of malaria worldwide to save may humans in 100 years from dying of sealevel rise of a whole foot or two. Governements and NGOs must immediately cease any anti-malarial programmes. Any staes within the EU that do not achieve their required increase in malarial mortality will be heavily fined and the money spent on a continent wide network of mosquito brreeding stations.

    Next month…more bad news! Cholera and plague down as temperature rises. We propose the drastic measure needed to combat this threat. Including the new songs..’Love your Buboes’ and ‘Don’t Diss that Dirty Water, Dude’ (remix)

  14. epolvi says:
    October 4, 2011 at 6:07 am
    From scientific process point of view I can’t see that the above eliminates the hypothesis that malaria is spread more at higher temperature but only shows how efficient DDT and other present means to fight malaria are.

    What it shows more than anything is the law of unintended consequences and the power of fear.

    Fear of malaria and yellow fever led to the widespread use of DDT to eradicate the problem in developed countries and once that fear was gone, the fear of DDT led to the widespread banning of DDT worldwide. As the fear of malaria has returned, so has the use of DDT.

    In the WHO handbook of disease from 30 years ago, Slim’s disease is listed as spread by mosquitoes and bedbugs. Slim’s disease was a wasting disease in Africa, now known as HIV. The notion that HIV has an insect vector has been routinely denied by health officials, yet there remain many cases of HIV that cannot be explained by any other means.

    The routine explanation that “the patients are lying” seems unlikely to be universally true. Science assumes that the chances of contacting HIV by way of insect vectors is small, due to the amount of blood exchanged, but small is not zero. HIV is not such a simple disease, the incubation time can be quite lengthy, making it difficult to be sure of cause and effect.

    This may have serious implications due to the widespread return of bedbugs in recent years. DDT wiped out bedbugs. Without DDT they have returned. The hotel bed you sleep in tonight may well have been slept in by a HIV positive individual the night before. Are you sure the bed is free of bedbugs? With improved treatment there are many more HIV positive individuals surviving for longer. This could be the heritage of the ban on DDT for the developed world.

  15. Dave Springer says:
    October 4, 2011 at 5:04 am
    The mosquito has a limited lifespan and by the time the temperature declines to about 20C the malaria parasite needs a longer period of time in the mid-gut of mosquito than the mosquito will live.

    Luckily for malaria that humans cannot survive below 28 C for any length of time without technology. The IR radiation from an unprotected human exceeds 150 W as temperatures fall below 28C, and 150 W is about the limit of heat the human body can generate over time.

    Luckily for humans, for most of the past 600 million years the average temperature of the earth has been 22C, which co-incidentally was the exact same temperature we find most comfortable to set our thermostats in our houses.

    Unfortunately with the invention of the ice ages, temperatures are now averaging around 14.5C, forcing many of us to have to burn fossil fuels to heat our houses. Hopefully in a couple of years global warming will heat the earth back up to its more typical long term average of 22C, thereby significantly reducing our home heating bills and our reliance on fossil fuels.

  16. In the cold north malaria was very largely transmitted indoors and in winter. Malaria was most common in the spring,
    The last major outbreak in northern Europe occurred in Finland in 1939/40 during the “Winter War”. This was an extremely cold winter, but lots of people were displaced by the war and had to live crowded into substandard housing which facilitated transmission.
    Even in the tropics indoor transmission is dominant, which is the reason mosquito-nets actually work.

  17. This paper shows that the relationship between temperature and malaria is not nearly as simple as assumed. The low temperature must be at the right time, and for the right length. Simple overnight cooling below 20C is not going to do it. Malaria can survive much lower temperatures. The 0.7C per century warming we have experienced for the past 300 years is not significant in comparison.

    For example, when we lived in PNG and Thailand, malaria was a disease found mostly in the highlands, where temperatures were routinely colder than on the coast. On the coast the main problem was dengue and malaria was quite rare.

    http://www.jstor.org/pss/3275577

  18. tty says:
    October 4, 2011 at 7:37 am
    Even in the tropics indoor transmission is dominant, which is the reason mosquito-nets actually work.

    That would explain why malaria was more prevalent in the highlands in PNG and Thailand, where it is colder, especially at night. People were more likely to be indoors at night to stay warm.

  19. Jessie says:
    October 4, 2011 at 5:19 am
    My experience from central Australia in the 1980s was when people left the main regional/community hubs to live on tiny outstations all of the above and sewerage systems were later installed under ‘development agendas’.

    In the south pacific one of the first development projects initiated by the missionaries was to site an outhouse over the lagoon to improve public hygiene. Rather than walk into the jungle to use the facilities, everyone was required to use the outhouse. The lagoon soon because the source of disease for the local population.

  20. So, malaria isn’t linked to temps……… again…….still…… as I recall, this was one of the first CAGW nuttburger fallacies put to bed, years ago. In fact, the link was falsified so long ago, I’d have to fire up my computer from 2 generations ago to find the references.

  21. The DDT ban-mass murder story is really getting old. There never was a world wide “ban” on DDT. It was banned for agricultural use, but not for infectious disease control. There also are DDT-resistant mosquito strains – if DDT had remained in more widespread use, no doubt these resistances would have spread further and rendered DDT less effective than it is now.
    The failure of effective malaria control in much of Africa during much of the recent decades is due to incompetent, corrupt governments, not to the misguided activism of some greenies.

  22. I just finished a “history survey” book by Charles (not Michael) Mann called 1493. It had a chapter devoted to Malaria and how the “tropical” disease was most likely brought to the Americas from the “Malaria Belt” in southeastern England.

    Yes, England. That tropical paradise. . . . . .

  23. Correct me if I am wrong, & I am ceirtain you will, but according to one of the world’s leading experts on Malaria, & other vector borne diseases, one Dr Paul Reiter from the Pastuer Institute in Paris, malaria is not temperature related per se, but rather dependent on socio-economic conditions, i.e. the poorer you are the more likely you would suffer from the effects of malaria! He also noted in his testemony to the House Of Lords’ Science Committee some years ago now, that the Parliament buildings were founded on a former malarial swamp, as indeed are those buildings in Washington DC!!! The British Royal Society for the Protection of Birds has recently celebrated the creation of costal swamp-like wetlands, ideal breeding grounds for malaria bearing mosquitos, brilliant, what geniuses they are!!! Holland only became malaria free in 1970 (WHO). Archangel in the Arctic Circle had one of the worst ever outbreaks in the 20s or 30s, where thousands died! Malaria or the “Ague” is mentioned many times in the plays of Shakespeare written in the 17th century!

  24. Read these and weep. When DDT was withdrawn from regular use, they were saying that Malaria was on the verge of being eradicated. Now there are around 1,000,000 dead from the disease each year. (More or less. Depends on who is doing the counting and their personal agenda.)

    http://www.cdc.gov/malaria/malaria_worldwide/impact.html

    http://archive.idrc.ca/books/reports/1996/01-07e.html

    http://www.cdc.gov/malaria/about/history/

    http://www.searo.who.int/en/Section10/Section21/Section334_4008.htm

    Malaria
    Malaria most likely is the greatest killer of humans in history. Even today, the World Health Organization estimates that it kills 2.7 million people a year; WHO says that it kills 2,800 children a day. The tragedy is that malaria is entirely preventable. After World War II, it disappeared almost entirely thanks to the use of DDT. However, with the banning of that pesticide, malaria has made a comeback. .

    http://www.aei.org/outlook/27063

    There is so much information out there that there is no excuse for not knowing.

    Regards,
    Steamboat Jack (Jon Jewett’s evil twin)

  25. Alan the Brit has beaten me to it in reminding everyone abour Paul Reiter, who years ago trashed the link between more warming and more malaria. He caused quite a stir by demanding to have his name taken off one of the IPCC reports because it edited out or somehow diminished his (unarguably) expert view. Because the AGW-ers are playing a political game, they think the ‘little people’ will be too stupid to remember stuff from 15 years or so ago, so they blithely wheel out again the old scare story, more warming = more malaria, knowing full well its been discredited. Completely. And they are scientists?

  26. DDT.was.never.banned.for.use.on.Malaria. Got it ? NEVER. 3,000 – 10,000 TONS are used NOW EVERY YEAR and have been for decades. The Bates know-nothings are quite annoying.

  27. The work sited significant warming over the last 10 years. I tried to find the numbers but they elude me. Anyone know what significant is?

  28. Steamboat Jack says: Read these and weep …

    I weep because I have to read drivel like this again and again. DDT is not a magic bullet, it remains available, it is easily synthesized, and it is not irreplaceable. The real cause of failures in the fight against malaria, as well as tuberculosis, as well as HIV, is poverty. Got it? TB is, or was, practically extinct in developed nations. Among developed nations, the U.S. give rise to and spread more resistant TB strains than others, which simply due to their dysfunctional system of health insurance. Now there is something for the market-solves-all-problems crowd to think about.

  29. I think Mike has brought up some very strong social economic points. Lots of good discussions from many others. We will continue to be bombarded with this pseudo science stupidity and much more too. All to many fool themselves substituting ideology and dogma for deductive reasoning and a broad base of factual knowledge.

  30. If this is a science blog, and the commentators want to make valid points, then they should at least try to get their science on a firm basis before spouting off. Human malaria requires a human reservoir of the disease (it is not a zoonotic), an appropriate vector (only mosquitoes in the genus Anopheles, and then really only those species that like to hang around where people do and bite them), and a long enough period of time above a critical temperature for (a) an Anopheles mosquito who has bitten someone with malaria to mature the infective stages of the malarial protozoan and (b) to find and bite another person. The shorter the period of time above the critical temperature, the less likely it is that malaria will be transmitted, even if you have a people with malaria feeding the right mosquitoes. Therefore, an increase in global temperatures could support the increase of malaria transmission at higher latitudes and at higher elevations.

    Since all of these conditions could be met in many parts of the world that once had malaria but are now malaria-free (e.g. most of Europe and North America, much of Asia and Australia), and since the purported increase in temperatures has not lead to a recolonization of these areas (in spite of the migration of many people carrying the disease into the malaria-free zone) indicates that other, more critical, factors are in play. The most important of these is undoubtedly a functional public health system and an absence of war.

    It isn’t a diminished ability to use DDT which has lead to the deaths of so many Africans from malaria over the last fifty years, but the decay of their public health infrastructure due to social upheaval. If our public health system fell apart, then we would have malaria again in a decade or two – even if the global temperature fell a few degrees and we had warehouses full of DDT.

  31. Dave October 4, 2011 at 4:19 pm said “requires a human reservoir of the disease (it is not a zoonotic)”

    Correct for 4 out of 5 Plasmodium species which cause Malaria. A fifth species, Plasmodium knowlesi, is a zoonosis that causes malaria in macaques but can also infect humans.

    “If our public health system fell apart, then we would have malaria again in a decade or two”

    Quite likely in a lot less time, depending completely on the numbers of human carriers in any particular area. The Anopheles spp. vectors are already present and disease endemism would take less than several year provided infective Plasmodium spp. was present and accessible by vectors in sufficient numbers in the local population.

  32. Anthony you said “….Nice idea, but call us cynical as we seriously doubt that we’ll be seeing this “iconic” figure in the IPCC’s next Assessment Report (AR5)!”

    I think we will see that chart but they will chop it off at 1995 and only show the increase.

  33. “If our public health system fell apart, then we would have malaria again in a decade or two”

    And exactly what public health measures is it that is keeping malaria at bay now? As is well known there is no vaccine. It is certainly not vector control – here in Sweden we have the misfortune to live in one of the worst parts of the World for mosquitos (a fair proportion of them Anopheles) and yet malaria went extinct almost a century ago.
    If it was public health measures that exterminated malaria, contemporaries were apparently unaware of them, they noted that malaria was gradually disappearing, but they had no clear idea why. And to speak plainly the Swedish public health system wasn’t that hot in 1850, or 1900 for that matter.

    It seems that the important thing is actually housing. When people live in reasonable houses, separated from their livestock and where lighting and general cleanliness makes it practical to get rid of insect pests indoor, malaria disappears. The livestock is important, for while human malaria does not infect other species, Anopheles mosquitos are highly dependent on livestock, at least the species occurring in northern Europe are.

  34. Malaria should not be allowed to exist in either a warmer or a colder world-period! It is disgraceful that the disease and the suffering it causes gets caught up in the politics of both the right and the left. Unfortunately for malaria victims- malaria eradication may be the first victim to suffer casualties inflicted by two environmental ideology wars some forty years apart (DDT and AGW)

    The CDC was formed for the initial purpose of combating malaria. Malaria was extinguished in the US by 1951 -semi tropical states and the colder northern states included. The threat of malaria is not climate -it is will, resources and public health infrastructure.

    And to Mike- DDT has a “de-facto ban” with foreign aid tied to a country’s promise not to use DDT. The biggest advantage of DDT may not be as a pesticide but the aversion response mosquitos have to its presence. Spraying DDT on the walls of rural abodes has a tendency to keep mosquitos from entering and its persistence is also a plus in those remote locations where public health workers cannot easily access at frequent intervals. I’m not saying DDT is any longer a silver bullet but in places it can be an important tool. Those of us who don’t face the malaria threat shout just butt out.

  35. tty – malaria is repeatedly introduced into Western countries and sometimes there have been localized outbreaks – in he US, Australia, etc. It is the public health systems – broadly defined to include mosquito abatement – that keeps it from establishing. I said nothing about exterminating malaria – you would have to exterminate the people who have malaria to do that.

    But you are right in a sense – screening and public health services that convince people to use various forms of screening are important. In Finland, houses were actually a critical factor in maintaining malaria by allowing Anopheles sufficient day degrees to mature their plasmodia. I haven’t seen a similar study for Sweden, but I would bet (a small amount) that it was true there too.

    BioBob – is Plasmodium knowlesi actually a significant cause of malaria in people? There are probably lots of other plasmodia out there that may someday cause problems, but right now we have the big two and the other two to worry about.

  36. Dave,

    P. knowlesi is found in SE Asia especially Borneo. In many of the affected areas it has been reported to comprise 70% of the reported malaria cases. Macaques of at least 2 species are the normal end-target of the P. knowlesi, but humans are commonly infected as well. Diagnosis often is confounded with Plasmodium malariae.

    Pat Moffitt October 5, 2011 at 11:23 am says:
    “DDT has a “de-facto ban” with foreign aid tied to a country’s promise not to use DDT.”

    Widely posted, actually completely false, in fact. More simply this is propaganda bullcrap.
    Any and all countries signatories to the Stockholm convention of 2001 / 2004 can apply for an will always receive permission to employ DDT for vector control and in fact any who have malaria problems have received permission for its use and have used megatons of DDT — some/much of which ends up used on crops via diversion due to corruption. DDT is so cheap that any country can afford to buy tons out of petty cash. Actually using it effectively is a different matter entirely

    Malaria persists not because DDT is not used but in spite of its continual use Use your imagination about WHY that happens considering the realities of corruption, stupidity, failures/lack of public health infrastructure, etc. You try to eliminate a insect that can reproduce by the hundreds in a wet footprint or old soup can in 10 days, fly unimpeded into a shack/mud hut in a village hundreds of miles from the closest clinic offering effective treatment of Plasmodium.. And good luck !

  37. I’m old enough (67) to remember when DDT was touted as the magic bullet for pest control. I recall the canal across the street being sprayed and the breeze blowing the noxious stuff towards the residences. Got rid of the mosquitoes… FOR TWO WHOLE WEEKS! Then they were BACK IN FULL FORCE.

    I don’t understand why so many people can grasp that AGW is a fabrication of the global elitists, but don’t seem able to comprehend that corporate Agribusiness invented the so-called Green Revolution that gave us the pesticides and herbicides that have caused so many illnesses and allergies. Do you honestly think that Monsanto has the best interests of humanity in mind and that if it weren’t for those dad-blamed hippie envarnmentists we’d be living in a bug-free paradise!? (Never mind that bugs, even annoying and disease carrying ones, are vital to ecosystems everywhere…)

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