|By RuthSponsler on Tuesday, November 09, 1999 - 04:10 pm:|
A. Recently, articles have been published in the New York Times and in the Guardian of London
concerning DDT and malaria control. The articles are available from this site. Please give an initial
opinion regarding the future need for DDT in malaria control. This may be very brief [one sentence or a
small paragraph], as we will go into this more deeply in the discussion.
B. Please give your impression of the current status of malaria in
1. Regions where DDT has been used historically or currently for malaria control and
2. Regions where DDT has not been used [or little used] historically for malaria control.
1) includes numerous locations in portions of Africa, Asia, South America, Europe, and Central/North
America. 2) includes mostly SubSaharan Africa. Compare the present status of malaria in each location
with the malaria situation of the 1950s 1960s and 1970s.
Please cite specific locations, case numbers and references for Part B of the question.
|By Anonymous on Friday, November 19, 1999 - 08:59 am:|
ddt IS HARMFUL TO OTHERS...I DON'T LIKE THIS USE AT ALL
|By RuthSponsler on Wednesday, November 24, 1999 - 02:28 pm:|
The anonymous poster, while certainly being able to get "their" point across with brevity, is most likely quite unaware of the number of lives saved and malaria cases that were prevented during the malaria eradication/control programmes that largely relied on DDT usage.
It is unfortunate that many of the gains made during these years are now lost and some are quite hard to recover, owing to parasite drug resistance and to insecticide resistance in some vectors, i.e. _An. stephensi_ in Iran and India. It is important to note that insecticide resistance is not a problem with all vectors.
|By KelyK on Tuesday, December 14, 1999 - 08:25 pm:|
Concerning DDT & the above two responses....yes, the first respondant was brief & did not back up his or her opinion....#2, I urge you to pick up a video titled "No Grapes". I have not eaten table grapes in YEARS because of the pesticide protest. I also protest the use of DDT for mosquito control. Please pay particular attention to the children of the migrant farm workers in the video who were BORN with cancer or who were BORN with their spinal column protruding from their backs!! Their are other, more organic, and most likely LESS EXPENSIVE options available for insect control.
|By Alex Carll on Tuesday, December 28, 1999 - 04:39 pm:|
I am interested in learning more about the debate surrounding UNEP's proposed ban on DDT. More specifically, what sparked the notable increase in the press's coverage of the ban--was it MFI's letter of protest to UNEP, WWF's study, UNEP press releases outlining INC3, some combination thereof, or other factors? It seems that the general public paid very little attention to the proceedings in the first two sessions of UNEP's treaty process, becomming interested only a week before INC3.
|By Roberts on Tuesday, December 28, 1999 - 06:39 pm:|
I am presenting some general observations, and specific comments to the query from Alex Carll.
Response to Anonymous contributor: The claim that DDT is harmful to human health is easily made. Please cite documentation that supports your belief that DDT is harmful to human health.
In my own work with the literature I find no evidence that human health improved as a result of banning DDT in industrialized countries. Likewise, there is no modern, replicated studies documenting harm to humans from public health use of DDT in developing countries.
Response to Kelyk: The reality of birth defects and children with cancer has nothing to do with DDT. Many studies have been conducted on relationships between DDT and cancer, so far there is no persuasive evidence that DDT is a meaningful cause of human cancers. Additionally, I know of no evidence that DDT is a cause of birth defects. If you know of such evidence, please cite the studies so others can evaluate the strength of the evidence.
Response to Alex Carll: The malaria problem has been increasing for many years. Growth in numbers of malaria cases has been accompanied by increasing concern of tropical public health workers. I am confident that science and health writers in the popular press have monitored these events. When the community of scientists, public health professionals and science writers finally realized that UNEP was moving to eliminate DDT, it brought this growing level of concern into the public arena. Against this background of growing concern, the MFI letter was a very valuable, honest and effective catalyst.
|By Simon Redding on Saturday, April 22, 2000 - 11:02 am:|
May I strongly recommend that all contributors to this debate go out and buy (and read) a copy of Silent Spring (R. Carson).
One of the key things to remember in this debate is that a malaria epidemic may only last a few years (or a generation), whereas the presence and effects of DDT can be noted over many generations.
I've been on the butt end of malaria and know what a terrible disease it is, but a chemical which creates such a toxic legacy will solve no society's problems in the medium to long term.
|By D. Roberts on Saturday, April 22, 2000 - 12:27 pm:|
Response to Redding: I suspect that many have purchased and read Silent Spring. More importantly, I suspect that many have actually studied the strength/validity of the supporting data of the claims/exaggerations in Carson's text.
The presence of DDT in the environment should not be classified as a problem unless a problem can be scientifically defined. If you have evidence that DDT on internal house walls is the direct cause of a meaningful adverse environmental effect, please cite the references.
I interpret your statement that you have been the butt end of malaria to signify that you have had malaria. If so, and as a matter of personal opinion, I do not think this qualifies you (any more than it qualifies me) to speak for all victims of malaria. After all, you are still alive. What about the millions who have marched prematurely to their graves as a result of malaria infections (mostly infants and pregnant women). In particular, I am thinking of the millions who have died in recent years simply because they have been denied the protective power of DDT sprayed house walls.
|By billholt on Thursday, April 27, 2000 - 09:31 pm:|
It would be amusing to see "Silent Spring" referred to as science if it weren't so depressing. But that's not really why I'm here. And although I've read a fair amount which convinces me that the ban of DDT was based on junk science, that's not my reason either.
I'm an engineer who works a great deal with surface water. On a mail list - called the "Water Forum" - I'm currently in a rather heated debate with several "environmentlists" who propose that introducing wetlands (love motels for mosquitoes) would have no detrimental effect in this country (USA). I understand that our annual infection rate is in range the one to two thousand, and recognize that this may not be a big number - depending on one's perspective - but I have real difficulty accepting the notion that more opportunities for a bad thing to happen is a good idea.
Here's the problem. Although it seems intuitively obvious to me that providing breeding opportunities in urbanized area will lead to more disease transmission, I haven't been able to find much data which says specifically that. Apparently, either I'm wrong or it's too obvious to have required a study in the modern context. The data I have presented is largely historical, as I do have some of that information for this urban area - Louisville, Ky..
My question/request - are there any such references? Could you point me toward a few, please? Anyone interested in seeing the debate that been going on can view it via this url: http://www.egroups.com/group/waterforum
You have to sign-up, but it's free.
If anyone sees this and cares to respond, please copy to my email address as I'm not sure when I'll find my way back to this location. The address is: firstname.lastname@example.org
|By Ruth on Friday, May 05, 2000 - 06:34 am:|
Correction/amplification: The approximately 1,000 malaria cases in the U.S. each year are almost all cases imported from other countries by travelers or immigrants. In recent years, very few autochthonous [locally-transmitted] malaria cases have occurred in the United States. There were two in 1999 and in 1998 I think there was a grand total of one.
In the United States, lifestyle changes, such as widespread usage of air conditioning and more time spent indoors have reduced the odds of local transmission of malaria from an imported case. This is not to say that cases could not happen, just that it is less likely than in countries where air conditioning and screening is used less.
To answer the question more specifically - mosquito populations depend on species, habitat and the ecology of the habitat. Wetland situations are very individual and the question cannot be given an accurate 'general' answer unless the precise habitat and mosquito species is specified.
Back to the DDT debate: The involvement of the United States in the DDT debate is almost purely administrative and political [i.e. the United States has plenty of resources and does not need DDT to control its mosquitoes]. The DDT debate concerns the United States as a donor and regulatory country with many more resources than malaria-endemic countries.
|By Ruth on Thursday, May 11, 2000 - 07:01 am:|
I want to bring people's attention to a couple of articles that are posted at this site concerning the outbreak of malaria in South Africa. The bottom line is that _An. funestus_ was found to have returned to the area after cessation of DDT usage in 1996. Unfortunately, it is not possible to control _An. funestus_ with pyrethroids, although South Africa's other vector species, _An. arabiensis_, is amenable to control with pyrethroids.
South Africa is experiencing the largest number of malaria cases per year since the 1930s. This is on top of a great deal of very serious health problems in the country, including AIDS and tuberculosis.
The situation with _Anopheles funestus_ is a superb example of the hazards of what would happen with a total DDT ban.
|By Colin Charles on Wednesday, June 14, 2000 - 06:40 pm:|
HelP! Malaria killed about 1.1 million Africans in the last 12 months, 700,000 of them were children. Malaria is easily preventable. We are just about to start our anti-malaria campaign and badly need a big close-up of a flying mosquito. ...
|By Colin Charles on Wednesday, June 14, 2000 - 06:40 pm:|
HelP! Malaria killed about 1.1 million Africans in the last 12 months, 700,000 of them were children. Malaria is easily preventable. We are just about to start our anti-malaria campaign and badly need a big close-up of a flying mosquito for TV. ...
|By AJIT V. ADYANTHAYA on Saturday, June 17, 2000 - 12:58 pm:|
DDT ban has resulted in resurgence of malaria in INDIA where it had been effectively controlled between 1947-1967.Mostly because of collapse of the governmental malaria control infrastructure due to lack of interest and lack of funds.DDT has a unique effect of controlling mosquitoes and avian reservoir for the protozoan.We are at present about to start a research project to validate the above hypothesis under the direction of Dr.B.S.KAKILAYA at the K.S.HEGDE MEMORIAL MEDICAL ACADEMY in Mangalore,INDIA.
|By Ruth on Friday, June 23, 2000 - 03:55 pm:|
Hello All -
I want to say that I agree with the points made about malaria control in the last post from India, but first need to correct a factual error.
Although birds may harbor species of _Plasmodium_, they do NOT harbor human malaria parasites and thus CANNOT serve as a reservoir of human malaria.
The first point regarding collapse of malaria control infrastructure and evaporation of funds is *correct.* Unfortunately, the crux of the DDT-malaria control problem is that governments, NGO's, and the private sector have NOT come together in an effective fashion with sufficient techniques adequate to replace DDT.
The NGO's that are vigorously pushing for a worldwide ban on DDT have not come up with malaria control programs of their own and are not doing field work with malaria control that I know of. I challenge them to develop an effective set of field-tested alternatives for malaria control and believe that would be a more laudable goal for their work.
Although DDT is not effective in all situations with all vectors, the following things need to be done before it is completely dropped from the malaria vector control arsenal:
1) vector control infrastructures will need to be aggressively rebuilt
2) ADEQUATE funding ensured for a fairly extensive period of time.
3) effective alternatives, and combinations of alternatives, to DDT for all situations available and actually IN USE.
To Mr. Charles - The MFI is working on an image library at this time. I apologize but cannot forward an image immediately.
We would also like to start a section of this website focusing on volunteers in Malaria - with communication aspects to assist the volunteers and NGO's in communicating with each other to get tasks accomplished. Could you kindly send some details of your work to email@example.com?
|By aadyanthay on Sunday, June 25, 2000 - 07:23 am:|
It is the exactly the " written in stone" attitude of people like jk55@hotmail that hinders progress in control of malaria.My implication was not that the avian parasite was the direct cause of human malaria but that it might have some influence by mutation or hitherto unknown reasons for the perpetuation of the disease; and that these factors must be researched.Incidently Sir Ronald Ross's extensive reseach with the discovery that the anopheles mosquito was the vector was the result of birds in Secunderabad in INDIA.AJIT V.ADYANTHAYA
|By aadyanthay on Sunday, June 25, 2000 - 07:29 am:|
ERROR IN MY PREVIOUS MESSAGE :IT SHOULD READ "result of study in birds" Ajit V.Adyanthaya
|By Ruth on Tuesday, June 27, 2000 - 06:03 am:|
To Mr. Adyanthaya -
Instead of noting that we *agree* on the major point of decrease in vector control efforts causing resurgence in malaria [that is most relevant to the topic of this board], and working *with* this agreement, you chose to pick an argument on your secondary point, and also to use the highly enlightened and scientifically progressive technique that is preferred by the most intelligent and courteous citizens, 'name-calling.' [sarcasm intended]
If you choose to argue, rather than to discuss how the problem of decrease in vector control efforts
can be solved, I strongly suggest that you find some good references with which to back your argument of possible involvement of birds in human malaria by using MedLine [PubMed] and other sources, including Dr. Ross's avian malaria work.
Personally, I prefer to work *with* people, rather than *against* them. I guess many others do not prefer to do that, however. This results in less constructive work being done, and the consequences rest upon the parties that pick the arguments.
A better topic for discussion on the topic of this board would be, "Can you share some concrete information on what vector control efforts have been performed in your district during the 1990's? What has been the epidemiology of malaria in your district? What factors impact those efforts?"
|By Dr. B. Srinivas Kakkilaya on Thursday, June 29, 2000 - 05:27 am:|
Hello everybody! Malaria has come back with a vengeance, there is no doubt about that. But is it only due to the ban on DDT? Can alone the re-use of DDT control malaria once again?
In India, there were 75 million cases of malaria in 1947 with more than 8 lakh deaths annually. With concerted antimalaria measures, that included spraying of DDT, the annual incidence came down to 50,000 by 1961. By 1965, the cases started rising again (nearly a lakh) and now it has spread to many newer areas with an annual incidence of about 2-3 million. Is this due to ban on DDT?
Use of DDT was never suspended in the National Malaria Eradication Programme in India. It is being used in the rural areas even today! Yet the disease has come back in most areas, rural as well as urban. So obviously it is not DDT but something else.
Even otherwise, does malaria control only mean use of DDT? DDT is a non-degradable, adult mosquitocide. Controlling the flying adult mosquitoes is probably the most difficult and most expensive way of containing malaria. The easiest methods are reducing the parasite load in the community by early diagnosis and prompt treatment (EDPT) and reducing the breeding sites of anopheline mosquitoes (Source Reduction). Both these do not require the use of even one drop of any insecticide! Beyond this, larvicidal measures can be undertaken with the use of biolarvicides like the guppy fish. Again no need for chemicals! Why run behind adult mosquitoes with DDT when you can kill millions of eggs and larvae without a drop of any insecticide?
We have developed a comprehensive malaria control strategy here at Mangalore that has involved various sections of the society, including even aquarists and fisheries scientists. Since 1995 this integrated strategy has been put into work. Fogging with deltamethrin was done in high risk apartments in 1996 and chemical larvicides were used in early part of the programme in 1995. After that not much of insecticides have been used and certainly never DDT. Yet the annual incidence has dropped from about 12,000 cases in 1995-96 to about 4000 in 1999.
May be therefore DDT is not the only answer to control malaria. If there is a will, there are many ways.
K.S. Hegde Medical Academy
Mangalore - 574160
|By AJIT V. ADYANTHAYA on Thursday, June 29, 2000 - 08:00 pm:|
To,RUTH SPONSLER,what you consider a secondary point might well be more important than you think.you made some very good points on vector control but one should realise that the malarial parasite life cycle is a complex one and when secondary reservoirs exist eradication could be wellnigh impossible and malaria control may well be the only option.Dr.B.S.KAKKILAYA an expert on the field on malaria control has agreed to post our experience.As to the fine art of name calling you are no slouch!with a dash of sarcasm you have done a fine job.DDT with its collateral environmental damage is not only ineffective but also a public health hazard.AJIT V.ADYANTHAYA
|By Ruth on Friday, June 30, 2000 - 06:11 pm:|
Hello All -
I absolutely agree that DDT is most definitely not effective against all vectors. In fact, in India, _Anopheles stephensi_ is one of the major problems and it is often a container breeder that is amenable to source reduction, screening of water tanks, and placement of larvivorous fish in the tanks. This vector has a unique habitat that makes it quite amenable to source reduction, and in fact, that should be done before resorting to any insecticide. Also, this vector is resistant to DDT in quite a few places, so I rather doubt if DDT is applicable in too many places vs. _An. stephensi_.
I certainly do not want to be misunderstood here.
I am against the ban on DDT because it is an effective tool in *certain situations,* NOT because it is universally applicable. It is not.
People who are trying to control malaria need all the possible tools available. But if you need a screwdriver for the job, don't use a wrench. However, in the situations where a wrench is needed there is a problem if it is not available in the tool box. The appropriate tool needs to be used for the job, and the appropriate tool is unique in every situation.
Vectors are very unique in their biology, and each situation has to be taken on its own.
Are you doing inspections of housing areas for _An. stephensi_ breeding and for source reduction work?
I see some contradictions in Mr. Adyanthaya's posts that I do not understand.
|By AJIT V. ADYANTHAYA on Saturday, July 01, 2000 - 07:55 am:|
Let me explain some of the contradictions.The point of the initial posting was that research was needed to find out whether DDT decreased the incidence of malaria by some effects other than its mosquitocidal effect; the latter being a known fact.For example its effects on the bird population or the malarial parasite itself.However as DR.Kakkilaya pointed out despite the use of DDT in India malaria has increased.However what was the quantity of DDT usagein the50s and60s ascompared to the 90swere they enough to affect the local bird population?so my statement against the use of DDT in my last posting was not a contradiction;I never was a proponent for the use of DDT.However if somebody can make a case for its use where the benefits outweigh the collateral effects I will change my mind.Now that we are engaged in a level headed discussion I must aknowledge Ms SPONSLER's extensive knowledge of the anopheles species; however as Dr.Kakkilaya pointed out as in a war it is more effective to destroy the factories producing the planes than trying to shoot them down from the air.AJIT V. ADYANTHAYA
|By Donald R. Roberts on Wednesday, July 12, 2000 - 03:00 pm:|
Prepared by D. Roberts
I have read with interest the recent posting on this bulletin board by Dr. Kakkilaya, Mr. Adyanthaya and Ruth Sponsler. I think each discussant has stated, in one form or other, that the use of DDT is only one possible approach to control of human malaria and that DDT is not equally efficacious in all settings. On this point I agree. I also agree with the three points listed by Ruth in her posting of 23 June 2000. However, there are other statements that warrant further discussion and I have worked with Ruth to prepare comments that represent our joint effort.
|By Donald R. Roberts on Wednesday, July 12, 2000 - 03:08 pm:|
Prepared jointly by D. Roberts and R. Sponsler:
In the 17 June posting by Mr. Adyanthaya, he stated that "DDT has a unique effect of controlling mosquitoes and avian reservoir for the protozoan."
This statement embodies two implications. First, it implies that human malaria has a bird reservoir. Second, it implies that DDT sprayed for malaria control (inside houses) kills birds.
It seems that the issue of birds as reservoir of human malaria has been discussed in subsequent postings and hopefully resolved with the understanding that birds are not reservoirs of human malaria (specifically, not reservoirs of Plasmodium vivax, P. falciparum, P. ovale or P. malariae infections).
In reference to DDT’s impact on birds, one of us (Roberts) has conducted vector research in and around DDT sprayed houses for almost 30 years and never observed any evidence that DDT sprayed inside houses had any impact on avians (and this includes domestic chickens that were often present in and around sprayed houses). Additionally, he conducted mosquito collections inside many DDT-sprayed houses and never was told by residents of sprayed houses that DDT harmed them, their domestic animals or wild birds.
Now, we understand that many studies have examined the impact of DDT on birds, some showing adverse effects, with others showing no detectable impact. These studies almost always used very high doses of DDT and were generally conducted in the laboratory. The results were often not consistent or confirmatory and often related to dosage levels far above the levels of DDT that would be encountered in natural environments. As a consequence, there is no clear, unambiguous answer to the question of what is the result from environmental exposures of birds to DDT. Regardless, and more to the point of this discussion, to our knowledge there is no study that shows an adverse impact of DDT on birds as a result of DDT on house walls.
Obviously, as with most scientists, we understand that broad-scale use of DDT in agriculture has potential for ecological harm, but that type of harm is not germane to the topic of DDT for malaria control. Perhaps Mr. Adyanthaya can enlighten us by citing references to studies that quantify an adverse impact on birds of DDT sprayed on house walls.
Dr. Kakkilaya in a June 29 posting poses the question of whether the resurgence of malaria in India is due to "ban on DDT"?
As a point of clarification, it is our understanding that there is no ban on use of DDT in India (at least not for malaria control). We believe Dr. Kakkilaya is referring to reduced use of DDT for malaria control, not a ban on the public health use of DDT. Please correct us if we are wrong.
We have conducted extensive analyses of national malaria control data from many countries of the Americas. There is an almost uniform association of increasing malaria with decreasing numbers of houses sprayed with DDT (Roberts et al. 1997). The analyses also show that with data for a particular country there is a repeated and predictable association between malaria cases and numbers of houses sprayed with DDT. In other words, the correlations are consistent across and within country data. Even when case detection and treatment effort remains constantly strong, numbers of malaria cases will still fluctuate with changes in numbers of houses sprayed with DDT. The differences in associations suggest that case detection is critical as a curative measure; but case detection and treatment is not strongly preventive (see Roper et al. 2000, Baird 2000).
Moreover, malaria incidence data is not always accurate (Abeysekera et al. 1997) and decentralization of vector control has hurt surveillance [case detection] and treatment. Results have been disastrous in some locations such as Madagascar (Mouchet et al. 1997), probably because of cessation of control efforts along with lapse in surveillance. Health services that had let surveillance and control efforts ‘fall through the cracks’ when international agencies and donor countries urged integration of vertical vector control programs into primary health care (World Health Organization 1993) are now forced to consider focused vector surveillance and control efforts once again because of the disastrous results of decentralization (Albonico et al. 1999, Mouchet 1998).
The question remains as to whether these associations (described above) are applicable to the malaria situation in India, and this question we cannot answer. However, we do know that the government of India is purchasing enough DDT to spray only about 25 % of houses of families that are at risk of malaria and visceral leishmaniasis [kala azar], and this has recently caused deaths in Bihar (Times of India 2000). DDT is very effective at preventing transmission of visceral leishmaniasis (Desowitz 1991, p. 65), and the resurgence of kala azar is linked to cessation of DDT spraying . Malaria rates will certainly increase if 75% of people in malarious areas are unprotected; likewise, if houses are not sprayed then kala azar will continue to kill.
Dr. Kakkilaya also posed the question "does malaria control only mean use of DDT?"
In our opinion endemic countries need all the malaria control measures that are available. So malaria control should encompass all methods that are affordable and that reduce disease transmission. As just one option, DDT on house walls prevents adult mosquitoes from entering houses (a repellency action), it causes mosquitoes to exit without biting (irritant action), and lastly, with prolonged physical contact, it kills mosquitoes (toxic action). A probability model recently published by Roberts et al. (2000) shows that of these three actions, the repellent and irritant actions are more important in breaking man-vector contact inside houses than is the killing action of DDT (Rozendaal et al. 1989, Roberts and Alecrim 1991, Grieco et al. 2000). Whether these phenomena govern the beneficial affects of DDT for controlling malaria in India requires further study. However, for An. culicifacies, a study by Shalaby (1965) strongly suggested that behavioral responses of An. culicifacies to DDT residues were the primary actions of DDT residues. Other studies (Das 1997) support Shalaby’s work.
Dr. Kakkilaya stated that "Controlling the flying adult mosquitoes is probably the most difficult and most expensive way of containing malaria."
We disagree with Dr. Kakkilaya. Residual spraying is the easiest and most cost effective approach to malaria control because it breaks man-vector contact. Regardless, there is still the need for other approaches, e.g., improved house construction, screening of houses, and thoughtful location of houses in relationship to larval habitats, environmental management techniques and biological control methods (Fullerton 1931, Gunawardena et al. 1998, Gamage-Mendis et al. 1991). Residual spraying and other techniques are not exclusive, and in fact, the techniques should often be used together. It seems probable that residual treatments are more effective in screened and tightly constructed houses than in poorly constructed houses.
Dr. Kakkilaya stated that "The easiest methods are reducing the parasite load in the community by early diagnosis and prompt treatment (EDPT) and reducing the breeding sites of anopheline mosquitoes (Source Reduction)."
We have already commented on the issue of early diagnosis and prompt treatment.
For the latter part of Dr. Kakkilaya’s statement, the posting was not clear about which malaria vectors were being discussed. We can only guess that it is either An. culicifacies or An. stephensi. These two species have very different habits. Anopheles stephensi is often found breeding in man-made locations such as water tanks and in some situations might be amenable to source reduction efforts such as screening of the tanks and placement of larvivorous fish in the tanks. Anopheles culicifacies has very different larval habitats, behavior, and insecticide resistance status from An. stephensi. Anopheles culicifacies breeds in clean water in rural areas and is much less amenable to control by source reduction.
The claim that source reduction is the easiest method of malaria control is not true, especially in the case of mosquitoes that do not breed in man-made habitats. Consider the issues of scale, if a vector has a flight range of only 500 meters, then control must be applied to all larval habitats within 500 meters of a household (many of the vectors in the Americas can fly much greater distances in order to obtain a blood meal). A buffer zone of just 500 m diameter around a house covers a surface of 785,398 square meters. We mapped all larval habitats within such a buffer zone for a house in southern Belize. We put this map into a geographical information system and calculated the surface area of habitats that needed to be controlled. The final estimate was over 140,000 square meters. This surface area for larval control compares with just 250 square meters of wall surface that need to be sprayed if you decided to spray the house instead of trying to eliminate mosquito larvae. Obviously there are other rural sites with much less area of larval habitats within such a buffer zone; also there are sites with even larger areas of larval habitats. In this setting source reduction is not an option. Ecologically sensitive wetlands would suffer and environmental activists would not let this happen—period! We have 3 vector species in the vicinity of the house site, described above. One breeds in swamp forests and Typha marshes. Another breeds in rivers and the third breeds in sun-exposed pools with vegetation. Although some habitats could be drained or filled in, most areas of habitat could not be touched. Regardless, look at the tradeoffs, 140,000 square meters for larval control versus 250 square meters of sprayed walls; and remember, many vectors can fly more than just 500 m to get to a house, so the buffer would need to be much larger.
While we are on the subject of source reduction, I want to suggest that this approach to disease control has already been tested on a grand, hemispherical scale and it has not proved to be effective. The test case we refer to is Aedes aegypti control in the Americas. As most are aware, Aedes aegypti commonly breeds in man-made habitats (artificial containers). For many years the Governments of the Americas have adhered to a community participation and source reduction approach to vector borne disease control, and have made efforts at educating local populations about proper disposal and removal of containers and breeding sources (Mazine et al. 1996, Fernandez et al. 1998). Some of the measures to control breeding of Ae. aegypti are inherently very simple, such as cleaning of washbasins, proper disposal of cans, disposable containers, and old tires, yet there is a big problem with getting sustained cooperation of people to "clean up the premises."
Along with emphasis on community participation and source reduction has been the inexorable re-invasion of all of the Americas by Aedes aegypti. This terrible vector has returned to practically every urban area in tropical and subtropical America, in spite of source reduction (Aviles et al. 1997, Aviles et al. 1999, Chiaravalloti Neto 1997, Pinheiro and Corber 1997, Van der Stuyft et al. 1999, Focks et al. 2000). Of course the re-invasion of the Americas by A. aegypti brought dengue fever, dengue hemorrhagic fever and a renewed threat of urban yellow fever. The reason I use the term "re-invasion" is because most countries of the Americas were free of A. aegypti for well over 20 years. The mosquito was eliminated by peri-focal spraying with DDT (Severo 1955, Cebret and Desire 1996, Fouque and Carinci 1996, Torres Munoz 1995, Camargo 1967, Soper 1964). Now, under source reduction, A. aegypti is back and the disease burden is spiraling upward. In summation, reliance on community participation and source reduction has been an unmitigated, hemisphere-wide, colossal disaster!! The true magnitude of this disaster can be appreciated by comparing the phenomenal successes of the peri-focal spray programs of the 1940s, 50s and 60s with progressive growth in disease burden during the 1970s, 80s and 90s.
Still, we admit that source reduction should work under some conditions. For example, when many people can be protected by attacking a relatively limited area of larval habitats. Such programs will probably require heavy input of professional expertise, supervision and resources. Perhaps the success story described by Dr. Kakkilaya is an example of such a program. This brings us to the conclusion that some disease transmission situations can benefit from a highly specific approach to control. However, for broad-scale application the methods must be widely applicable, affordable and efficacious? Deficiencies in public services may cause problems (Barrera et al. 1995). Administrative controls [e.g., regulations that order all disposable containers be removed from premises and water tanks be screened] require a strong commitment from public authorities to vector control, which is difficult with decentralized health services.
In the case of Ae. aegypti control, the results (Monath 1994, Focks et al. 2000) of hemisphere-wide reliance on source reduction in the Americas suggest that source reduction is not widely applicable, affordable or efficacious. There is a need to implement control measures against Ae. aegypti at the national and continental level and history suggests that it is difficult to maintain low dengue transmission rates without doing so, even in areas subject to intensive surveillance and prevention (Passos et al. 1998). Source reduction is even less applicable, affordable and efficacious when we restrict our deliberations to the specific issue of malaria control because most malaria vectors, unlike Ae. aegypti, do not breed in man-made containers. An important exception is An. stephensi, the urban vector of malaria in India.
Dr. Kakkilaya stated that "May be therefore DDT is not the only answer to control malaria. If there is a will, there are many ways."
We agree: DDT is only a tool that can be used to control malaria transmission against some vectors, but perhaps not all. There are many differences in behaviors and physiological response of malaria vectors to DDT (Ismail et al. 1975). However, DDT is very effective against certain vectors, such as An. funestus in areas of seasonal transmission (Mouchet et al. 1997, Hargreaves et al. 2000). Anopheles funestus is a highly efficient vector of importance second only to the An. gambiae complex in Africa. Anopheles funestus was virtually eliminated from large portions of South Africa by spraying insides of houses with DDT during the 1950s through 1996. When treatment was changed to deltamethrin, malaria incidence in KwaZulu Natal increased over six fold (Hargreaves et al. 2000). A similar massive resurgence in malaria occurred after cessation of DDT treatment in Madagascar (Mouchet et al. 1997, Laventure et al. 1996, Mouchet 1998). Thus we conclude that DDT continues to be a vitally important tool that is still needed for malaria control.
As a final point, this discussion is not dedicated to the subject of DDT because DDT is the only tool in our malaria control arsenal. We dedicate time to this subject because there are groups and organizations who are working for the complete elimination of DDT. In other words, they want to eliminate it as a malaria control option. Many scientists do not think this is justified, fair, ethical or moral.
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|By Dr. Rajeev on Wednesday, July 19, 2000 - 09:39 pm:|
This ongoing discussion reeks of strong smell of a typical shouting match. Ruth started off with DDT as main topic, has now gone on back foot. Ruth & Robert seem to be isolated in their stance for DDT. What they don't know is that DDT is demonised in many parts of the world including urban India, not since any one was found to be suffering the bad effects. Many of us (elderly youth) have grown up with a strong sense of anti DDT in our blood. It is more emotional than scientific. We never had to really suffer the bad effects of malaria any time in our life than in recent years. We have noted the same streak of panic among the initial responders of this discussion who had nothing to say except about 'silent springs & No grapes.
Now to clarifications. We are battling An. stephensi in Mangalore which is not exactly known for its resistance in India. In fact it is the rural vector, An. culicifacies which is notorious for its triple resistance which incidentally was reported initially from our state Karnataka. But the problem is that indoor residual spraying in Mangalore is an impossible task. In typical flight range of 500 meters there will be hundreds of flats which would pose an impossible, uneconomic option leave alone the question of DDT as the weapon.
Residual treatment is a concept due mainly to DDT & the residual action of the chemical itself is the main disadvantage as well! As argued, DDT is not against flying mosquitoes, of course surely not against flying birds also. The superstitions regarding DDT has reached epic proportions. DDT as pointed out is ONE of the anti-insect weapons. I would like to promote DDT against sand flies for control of visceral leishmaniasis at the risk of running high emotions in environmentalists. DDT here would have to be used outside houses. Like the study by Roberts, one could also
prove that cases of Kala azar in India has been on the rise ever since DDT was being phased off in National Malaria Eradication programme.
Newer chemicals like pyrethroids were found effective in many places against the malaria vectors in India including Mangalore. However since one can't support wastage of these chemicals indiscriminately outside houses, one would rather go back to good old DDT than these. MFI may not be alone in supporting DDT. But question is how to remove the scar created in the moods of people against it? Would anybody pardon us if something were to be concretely proved later on. There were & still are skeptics on the use of small pox vaccine. Also penicillin in our part of the world is best known for anaphylaxis than its life saving properties.
Assistant Professor of Community Medicine,
Kasturba Medical College
|By Anonymous on Tuesday, August 22, 2000 - 10:55 am:|
|By James W. Thornburg on Wednesday, August 23, 2000 - 12:19 am:|
I often suffer from malaria...I have lived in Nigeria from the time that I was 3 years old until now... i am currently 18. Because I know first hand the devastating effects that malaria can have, I say that controlling this disease is imperative. I and my family are lucky: we have enough money to afford the treatments necessary to counteract malaria. I have held babies in my arms as they died with the disease...it is awful.
I also realize that the DDT is harmful to the people yet to be born, and to the environment. Isn't there any other way that this deadly disease can be controlled? If the answer is no, I can see no alternative but to use it...as much pain as it will cause later, think of how many lives will be saved....even if some are ruined. I know that sounds heartless...but millions of children die from malaria...and you just have to hold an infant...its body burning with fever, shivering violently to overcome chills...and your heart will melt, and you will understand what awesome proportions controlling malaria can mean.
|By GraSTains on Sunday, August 27, 2000 - 05:28 pm:|
I have developed a fertilizer with "insectifuge" capabilities. I have tested it throughout the Boise, Idaho area with great results. This product not only stimulates the growth of plants but I have testimonials from my customers (and myself) that it kills small insects like mosquitoes, flies, aphids,and small leaf-hoppers.
I want to field test my product on other insects and in other areas of the world. Can anybody help me to obtain this goal?
|By AJIT V.ADYANTHAYA on Sunday, September 03, 2000 - 09:18 am:|
Hi everybody,I thank Dr.Roberts for his excellent review on vector control; but I would feel much better about it if he could give the reference on his studies on household animals and birds in areas sprayed with DDT (WALLS).I do not understand why Dr.Kakkilaya's excellent posting on non-DDT control of malaria was removed after it was posted.It was Voltaire who said" I disapprove of what you say but I will defend to death your right to say it".The onus is on the proponent to provide data that it is not harmful to household animals and birds.I thank Dr.Rajeev for his balanced discussion which says itall in that region.However look at the wide array of antibiotics fear of penicillin has produced!AJIT V.ADYANTHAYA
|By Anonymous on Tuesday, September 26, 2000 - 07:45 pm:|
please help! my husband contracted malaria 5 months ago while traveling in s. america. my problem is that now he is having problems relating to his mental health. he is hallucinating and having traumatizing dreams and seems to be off in another world lately. this is affecting his every day life, and quite literally driving him crazy. i am wondering if this could be a result of malaria, or his high fevers (which reached 106 F), or the medication he was given (which included quinine and doxycycline).
i would greatly appreciate any direction as to where to find information about the long term affects of malaria and the medications. or any answers to my questions. please email me directly or post to this board.
|By Ruth on Friday, September 29, 2000 - 11:54 am:|
This board had a significant server problem that lasted several weeks. It has been fixed.
The Malaria Foundation International apologizes for the inconvenience that this has caused.
Please re-post the message(s) that were lost, as neither of the moderators has a copy. [Personally speaking, I was out of town when the message was lost, which is why I don't have a copy].
I need to reassure all that the loss of the message(s) had nothing to do with the content of the message(s).
|By Ruth on Friday, September 29, 2000 - 12:04 pm:|
For the person who contracted malaria: I recommend that a specialist in tropical medicine be contacted.
There is a list of travel medicine providers at
and a number of these, especially the major clinics related with universities [e.g. Johns Hopkins] are specialists in tropical medicine.
|By Anonymous on Tuesday, October 31, 2000 - 07:51 am:|
According to Rachel Carsons book Silent Spring, ddt has been the detriment of many birds of prey etc. However, maybe more localised spraying should be employed rather than widespread spraying.
|By Eduardo Ferreyra on Monday, April 09, 2001 - 04:53 pm:|
There is no possible stretching, twisting or manipulation of facts that could justify the criminal ban on DDT. Every single claim voiced by its opponents have been demonstrated as false, biased, distorted, and lacking any peer-reviewed, replicated study. Any further insistence on keeping such a criminal ban denotes a religious belief on superstition, utter ignorance and a credulous nature -or a vested interest in keeping the neo-colonial intentions of curbing world population by forcing millions of peolpe to die victims of diseases that were almost conquered.
I have been working and travelling in the Amazon jungle since 1970, following my father«s example: he explored the Bolivian Amazon from 1918 to 1921, and contracted malaria as everybody did in those regions by then. Although he returned to a non malarial region, in Cordoba, Argentina, he suffered two or three malaria attacks every year until he died in 1963, at age 73.
I visited almost any place in the Amazon, from Iquitos, Perú, to Belém, Brazil; from the Casiquiare River to the Guaporé, from the Tiriós Mission on the Brazilian border with Surinam to the Matto Grosso; from the Wichimi river in the Ecuadorian jungle to the Río Blanco in the Bolivian Amazon; from 1970 to 1997, when I said "that«s enough".
When working along with the medical students of Projeto Rondon, in Brazil, 1971, we saw and treated any kind of tropical diseases. Not strangely, malaria was the great absent. Those were the last years of the great Brazilian program of DDT spraying, carried away by the National Malaria Service. We carried everything needed to fight malaria itself: Daraprim, Aralén, Camoquin, Cloroquin, etc. We always returned home with the supply intact. I never met anyone with the fevers so common in my father.
Now, after Brazil and Argentina stopped using DDT, Malaria, Dengue, Leishmania, etc, are back, along with body and head lice, fleas, and ticks responsible for deadly diseases as haemorraghic fevers (so common now in Argentina«s Pampas), leptospirosis, Lyme disease, etc.
The preposterous claim that DDT provokes cancer didn«t stop me from following the results of studies by Edward R. Laws et al (1), and Charles Silinskas and Alan E. Okey (2) that proved that DDT is a strong anti-carcinogen in rats and humans: since 1995, after receiving radio therapy for a prostate cancer, I started taking a daily dose of 15 mg of DDT. My prostate antigen analysis level is about 0.1 --for an age of 63 this is remarkably low. Had DDT been the deadly pison claimed by Raquel Carson and her gullible followers, I would have been buried in my grave long ago.
President of FAEC
Argentine Foundation for Scientific Ecology
(1) E, R. Laws, , A. Curley and F.J. Biros, Archives of Environmental Health, Vol. 15, pp. 766-775, (1966) and Vol. 23, pp. 181-184, (1971)
(2) Charles Silinskas and Alan E. Okey, 1975, "Inhibition of Leukemia by DDT", Journal of the American Cancer Institute, Vol. 55 (Sept.), pp. 653-657.
|By ohdamn on Tuesday, July 10, 2001 - 10:08 am:|
im going to die
the doc sed 2 days ago i have 3 days to live
im only 17!!!!