French version available in IDRC Digital Library: Lutter contre le paludisme sans DDT : le contrôle de la maladie passe par une meilleure gestion de l'environnementSpanish version available in IDRC Digital Library: Combatiendo a la malaria sin DDT : mejor manejo ambiental, clave para el control de la enfermedadUnder the terms of the North American Free Trade Agreement, Mexico was
committed to eliminating DDT use by 2002. The country’s malaria-control efforts,
however, depended on this chemical. Researchers set about to develop alternate
strategies by addressing factors that affect malaria’s spread: humans, mosquitoes,
and the local environment in which the parasites persist. As a result of this
integrated approach, Mexico was able to abandon DDT ahead of schedule

Amirov R.

Antipin I.

Elistratova Y.

Konovalov A.

Mustafina A.

Pilishkina L.

Zairov R.

Colloid Journal

The extraction of gadolinium(III) and lanthanum(III) ions at the cloud point is studied in Triton X100 micellar solutions in a wide range of pH. In the absence of chelating agents, lanthanum(III) and gadolinium(III) ions are unselectively extracted at pH > 6. It is shown that the use of p-sulfonatothiacalyx[6(8)]arenes as chelating agents noticeably enhances the degree of extraction at pH 2-6. The composition and stability of lanthanum-p-sulfonatothiacalyx[n]arene complexes (n = 4, 6, 8) are estimated in a wide range of pH by pH-potentiometry. The degree of Gd3+ and La3+ ions extraction, which is performed at the cloud points employing calyxarene macrocycles of different sizes, is depended on the acidity of a medium. © 2009 Pleiades Publishing, Ltd

National Open Repository Aggregator (NORA)

Extraction of lanthanum and gadolinium(III) at the cloud point using p-sulfonatocalyx[n]arenes as chelating agents

Pepall, Jennifer

International Development Research Centre: IDRC Digital Library

The black-and-white film footage from the 1950s shows theassault. A small army of men outfitted in protective clothing and masks advances on a village, spray canisters slung over their shoulders. The enemy — mosquitoes that carry malaria. The weapon of choice — DDT.Fast-forward a few decades to Oaxaca State, Mexico. Severalwomen, ankle-deep in water, throw green mats of algae ontothe riverbank. With each toss of the pitchfork, thousands of mosquito larvae lose their habitat.The women are part of a successful Mexican initiative that isfighting malaria on many fronts. Through community involve-ment in control strategies, improved surveillance and treatment,and the use of new household spraying techniques, Mexico has dramatically reduced malaria transmission. In 2001 therewere just 4,996 cases of malaria — down from 15,121 in 1998.Significantly, this decrease came about without a drop of DDT. Researchers supported by Canada’s International DevelopmentResearch Centre (IDRC) have been central to this success. Dr Mario Henry Rodriguez, Mr Juan Eugenio Hernández, andtheir research team have been working on malaria control inOaxaca State, a part of Mexico where the disease is particularlypersistent. With support from several donors and institutions,they are using an ecosystem approach to understand the com-plexity of the disease and the environment in which it flourishes(see box: Ecosystem Approaches to Human Health).  The projectthey lead has helped Mexico eliminate the use of DDT in justthree years. In doing so, it has become a model for othermalaria-control programs in the region.Malaria in MexicoMalaria has long been a public health problem in Mexico, whereconditions in 60% of the country are favourable to malaria trans-mission. In the 1940s and 1950s, malaria claimed an average of24,000 lives each year and afflicted some 2.4 million people. The government introduced a malaria-eradication program thatwww.idrc.ca/ecohealthFighting Malaria Without DDTBetter management of the environment a key to disease control Under the terms of the North American Free Trade Agreement, Mexico wascommitted to eliminating DDT use by 2002. The country’s malaria-control efforts,however, depended on this chemical. Researchers set about to develop alternatestrategies by addressing factors that affect malaria’s spread: humans, mosquitoes,and the local environment in which the parasites persist. As a result of thisintegrated approach, Mexico was able to abandon DDT ahead of schedule.9C a s e  s t u d yHealthAN ECOSYSTEM APPROACHIDRC: Peter BennettTreatment is delayed when malaria is diagnosed throughlaboratory analysis of blood samples, which can take up to 28 days. relied on extensive household spraying with DDT and anti-malarial therapy. Cases declined, but it proved impossible tocompletely rid the country of the disease. The problem was most stubborn in coastal areas, where control measures only succeeded in interrupting malaria transmission. This was demon-strated in dramatic fashion in 1997, when Hurricane Paulinacrashed into Mexico, leaving fertile breeding grounds for mosquitoes in its wake.  Of the 16,000 cases of malaria that followed, 12,000 were in the coastal state of Oaxaca. The outbreak triggered a search by Mexico’s National Institute ofPublic Health (NIPH) for new approaches to malaria control thatconcentrated on “pockets” of persistence. There was a secondchallenge — within the framework of the North American FreeTrade Agreement, Mexico was committed to reducing DDT useby 80% in 2000 and eliminating it completely by 2002 (see box:Banning DDT). Any new strategies to fight malaria would haveto do without a chemical mainstay of past control programs.Institutional collaborationThis ambitious goal called for the involvement of several institu-tions, including the NIPH, the National Centre for EnvironmentalHealth, the Malaria Control Program (MCP), and the Centre for Integral Training of Community Promoters. Dr Rodriguez,Director of NIPH’s Centre for Research on Infectious Diseases, andMr Hernández, the Institute’s Director of Informatics, undertookan extensive and varied research program. IDRC, Mexico’sMinistry of Health, the North American Commission forEnvironmental Cooperation, and the Mexican National Councilfor Research and Technology supported various components of the research. The researchers adopted an ecosystem approach to better under-stand the complex set of factors that influenced the incidenceand spread of malaria in Oaxaca. “We’ve looked at malaria frommany angles, including the molecular biology of the vector andthe parasite, community perceptions of malaria, statistical analy-ses, and a geographic information-based surveillance system,”says Mr Hernández. The team included specialists from several disciplines: epidemiol-ogy, informatics, entomology, and the social sciences. Before theproject, the researchers had been working on separate areas ofinquiry. The “ecohealth” approach, however, brought a measureof both collaboration and coherence to the research. “Ecohealthis a dynamic process that integrates the views of various disci-plines as well as those of the stakeholders,” says Dr Rodriguez.“It’s a way of systematizing the research.” Importance of GIS To help assemble the pieces of the malaria puzzle, the projectused a geographic information system (GIS) — a computerizedmapping tool that processes and synthesizes data from manysources. The GIS application covered more than 2,000 villagesand included data on elevation, climate, average rainfall, insecticide spraying, distance to rivers and roads, and short-rangehuman movements. By analyzing the GIS maps, researchers identified areas of highmalaria risk. They found, for example, that the closer a villagesits to a main road, the more likely its inhabitants will contractthe disease. Research on the ecology of mosquitoes pointed tothe reasons why. “Mosquitoes don’t move around much,” says Dr Rodriguez. “If you have a place to lay your eggs and get yourfood, why do you have to visit somebody else?”In other words, although mosquitoes transmit malaria, infectedpeople are responsible for spreading it. When there is easyaccess to a major road, malaria travels along it. “We are viewinghumans as the real vector, with mosquitoes as the dispersingagent in the very local environment. But human beings aretransporting the disease further away,” stresses Mr Hernández. How malaria spreadsWith the help of community members, researchers looked moreclosely at how people were contracting and spreading malaria.They gathered basic demographic information and examinedsuch factors as the condition of bednets, type of housing, andIDRC: Peter BennettBednets help keep malaria at bayIDRC: Peter BennettVolunteer health promoters help identify the risk factors that makehouseholds and individuals susceptible to malaria.the presence of animals and vegetation near homes. Theresearch also looked at gender differences associated withmalaria transmission. Women typically fetch water early in themorning — a time when malaria-bearing mosquitoes are biting.Similarly, men are at risk if they spend the night on coffee plantations where they have no protection against the insects. Data showed that about half of all the malaria cases wererelapses. “If you think that after you treat a community, it is freeof the parasite, it is not true,” says Dr Rodriguez. “It is dormantin the liver of the patients. When the mosquitoes come back, theparasites wake up and malaria returns.” GIS maps reinforced thisinformation by showing how malaria was a “repeat offender” in certain households. In San Rafael Toltepec, for example, 78%of the malaria cases were in 28% of the houses. Focal controlFor this reason, public health authorities introduced focal or targeted control of malaria. People who have had malaria theyear or two before are given preventative medication during the malaria “high season.” Their houses are also sprayed with apyrethroid-based insecticide that, unlike DDT, does not persist inthe environment. “In this way, we think we can block the cycleof transmission and relapse,” says Dr. Rodriguez. “It’s importantthat we don’t give prophylaxis to everyone, mainly because ofthe cost but also because the malaria parasite will becomeincreasingly drug resistant.” Dr Rodriguez and other malaria control officials are also promot-ing a new approach to insecticide spraying. Using a newly devel-oped mechanical pump, two people can spray about 40 housesper day, compared with 8 houses using a manual pump. “Thismeans people are being protected faster, and at the same cost as the previous technology,” Dr Rodriguez says.Community actionCommunity involvement is critical; villagers are literally gettingtheir feet wet in the fight against malaria. Work parties, madeup primarily of women, wade into water near their villages everytwo weeks to remove algae. By getting rid of the plants, the villagers deprive the mosquito larvae of their habitat and popu-lations of the insect subsequently decline. The community also collaborates in testing new methods of surveillance. The conventional approach to diagnosing malaria isthrough laboratory tests. Blood smears from people with malariasymptoms are then sent to a hospital for analysis — a processthat can take up to 28 days. If the test proves positive, thepatient is treated. But the delay between testing and treatmentmeans that malaria continues to be transmitted.The project is evaluating a new test that provides more than arapid diagnosis of malaria. “We consider it an intervention too,”says Dr Rodriguez. “The most important thing is to catch andstop the outbreak. For that, we need a surveillance mechanismthat is effective and timely.” The test involves placing a drop ofblood on a dipstick, which is put in a reagent mixture for 15 to30 minutes. If the test is positive, complete treatment can beginimmediately and the transmission cycle is broken.Volunteer health workers are assessing the rapid diagnostic testin more than 60 communities. If it proves to be accurate, “weare empowering the community to treat themselves,” says Mr Hernández. Communities are also learning how to reducetheir exposure to the disease from an educational video. Fromsleeping under bednets to chopping shrubbery and removingalgae, people can take malaria control into their own hands. Interventions a success Statistics show that the interventions are working. In 2002, therewere only 237 cases of malaria in Oaxaca State. Researchers arenow studying community perceptions of malaria and malariacontrol to understand the reasons behind this success.IDRC: Peter BennettDespite control efforts, malaria has been a persistent problem in thefoothills and plains of the coastal state of Oaxaca, Mexico.Banning DDT: a tale of two prizesIn 1948, Paul Hermann Müller won the Nobel Prize for his discovery that DDT was a highly effective insecticide. When itwas widely used to fight insect-borne diseases, the WorldHealth Organization estimated that it saved 25 million lives.Today, the chemical has gone from saviour to scourge becauseof its harmful effects on the environment and to humanhealth.Canada and the USA banned DDT in the 1970s, but it was stillused to control malaria in Mexico. In 1997, Canada, Mexico,and the USA established a North American Regional ActionPlan on DDT as a way to cooperate and share experiences inphasing out the substance. The resulting malaria-control program was so successful that Mexico stopped using DDT twoyears ahead of schedule.The Mexican model is an integrated strategy based on com-munity participation, prevention, and improved diagnosis andtreatment. For their contributions to developing thisapproach, Mr Hernández and Dr Rodriguez were awarded theJorge Rosenkranz Award in October 2002. The prize aims tostimulate scientific research and reward academic excellence.“We are taking a step back,” says Dr Rodriguez. “Disease trans-mission and control might be understood differently by theresearchers and the communities.” For example, people who hadcontracted malaria five years ago might say that they have nothad the disease. “For them, it is only this year that counts,” saysDr Rodriguez. Moreover, many people consult a traditionalhealer or saurin when they have malaria. For these patients, acurse — not a parasite — is causing their suffering. Even the removal of the algae has challenged researchers’assumptions. According to Dr Rodriguez, the women are clearingthe algae because the task is identified as a community endeav-our, not because of its connection to malaria.For these reasons, Dr Rodriguez underlines the importance ofcontinued research. “Our experience is leading us to new under-standing that we need to do more social research if we want toexpand these interventions to other parts of the country and tomaintain them in Oaxaca,” he says. “My impression is that wehave something that might work. The challenge is to find thelessons that can be applied in a general way to really make a dif-ference.”This Case Study was written by Jennifer Pepall, a writer in IDRC’sCommunications Division.www.idrc.ca/ecohealthEcosystem Approaches to Human HealthHuman health and well-being are intimately tied to the health of the ecosystemsthat sustain life. Yet the potential for improving health by better managing thelocal environment is an avenue rarely explored in mainstream health program-ing. Through its Ecosystem Approaches to Human Health (Ecohealth) ProgramInitiative, IDRC aims to identify the web of economic, social, and environmentalfactors that influence human health. Communities can then use this knowledgeto better manage ecosystems and improve the health of both people and theecosystem.April 2003 CASE-ECO-9EFor more information:Dr Mario Henry Rodriguez Mr Juan Eugenio HernándezDirector, Centro de Investigación de Director de InformáticaEnfermedades Infecciosas Email: juan_eugenio@insp.mxEmail: mhenry@correo.insp.mxInstituto Nacional de Salud PúblicaAv. Universidad 655, Col. Sta. Maria AhuacatitlanCP 62508Cuernavaca, Morelos MexicoTel: (+52-73) 29-30-55Fax: (+52-73) 17-57-45IDRC: Peter BennettA mechanical pump for spraying pyrethroid-based insecticideshas helped eliminate DDT in Mexico. Ecosystem Approaches to Human Health Program InitiativeInternational Development Research CentrePO Box 8500, Ottawa, ONCanada  K1G 3H9Tel.: +1 (613) 236-6163Fax: +1 (613) 567-7748Email: ecohealth@idrc.caWeb: www.idrc.ca/ecohealthThe International DevelopmentResearch Centre (IDRC) is a publiccorporation created by the Parliamentof Canada in 1970 to help researchersand communities in the developingworld find solutions to their social,economic, and environmental problems.Support is directed toward developingan indigenous research capacity tosustain policies and technologiesdeveloping countries need to buildhealthier, more equitable, and moreprosperous societies. 