Malaria Control: Latin America- The control of malaria in Brazil.
- Eradication of Anopheles gambiae from Brazil: Lessons for malaria control in Africa?
- Role of residual spraying for malaria control in Belize.
- Malaria control reinvented: Health sector reform and strategy development in Colombia.
- Zapping mosquitoes with biopesticides
- Agricultural Colonization and Malaria on the Amazon Frontier.
- Overview of malaria control in the Americas.
- Selective and conventional house spraying of DDT and bendiocarb against Anopheles pseudopunctipennis in southern Mexico.
- A comparison study of house entering and exiting behavior of Anopheles vestitipennis (Diptera: Culicidae) using experimental huts sprayed with DDT or deltamethrin in the southern district of Toledo, Belize, C. A.
- A field trial with Lambda-cyhalothrin (ICON) for the intradomiciliary control of malaria transmitted by Anopheles darlingi root in Rhondonia, Brazil.
- The phasing out of DDT in Mexico.
1) Gusamo, R. The control of malaria in Brazil. In The Contextual Determinants of Malaria. ed. Casman, E.A. and H. Dowlatabadi. Washington D.C.: Resources for the Future, 2002. pp 59-65.
PANNA summary: This chapter details the factors leading to the current resurgence of malaria in Brazil. In recent years, however, the situation has begun to improve. With WHO’s switch to the Global Malaria Control Strategy in 1992 (Brazil was the first nation in the Americas to switch over), priorities for control changed to more local and individually focused strategies, including early diagnosis and immediate treatment, small-scale preventative vector control measures, early detection and control of epidemics, and analysis of ecological, social, and economic determinants of the disease in order to develop new integrated control strategies. The result was a massive amount of energy poured into the implementation of the new strategy in effected communities. The results were very good, with over 8 million disability-adjusted life years saved due to preventative measures and improved diagnosis and treatment.(no abstract available)
2) Killeen, G.F. and U. Fillinger, I. Kiche, L.C. Gouagna, and B.G.J. Knols. Eradication of Anopheles gambiae from Brazil: Lessons for malaria control in Africa? The Lancet, Infectious Diseases, vol 2, October 2002, p. 618-627.
PANNA summary: Ever since the development of DDT as a tool for vector control, the focus of control efforts has been on controlling populations of adult mosquitoes. The authors argue that given the limitations of current methods—indoor spraying, bed nets, etc.—greater attention should be paid to successful control strategies from the past, especially larval control methods that successfully eradicated A. gambiae from northeast Brazil and the Nile River valley of Egypt in the 1930s and 40s. Though there were other types of spraying involved in the campaigns, the bulk of efforts were on spraying and dusting Anopheles breeding sites with Paris Green. Though the toxicity of Green has since been established, the authors argue that the success of this focus on control at the larval stage of development should serve as a lesson to current control efforts in Africa, and an impetus for researchers to continue investigating this approach where they left off over fifty years ago.
Abstract: Current malaria-control strategies emphasise domestic protection against adult mosquitoes with insecticides, and improved access to medical services. Malaria prevention by killing adult mosquitoes is generally favoured because moderately reducing their longevity can radically suppress community-level transmission. By comparison, controlling larvae has a less dramatic effect at any given level of coverage and is often more difficult to implement. Nevertheless, the historically most effective campaign against African vectors is the eradication of accidentally introduced Anopheles gambiae from 54000 km(2) of largely ideal habitat in northeast Brazil in the 1930s and early 1940s. This outstanding success was achieved through an integrated programme but relied overwhelmingly upon larval control. This experience was soon repeated in Egypt and another larval control programme successfully suppressed malaria for over 20 years around a Zambian copper mine. These affordable approaches were neglected after the advent of dichlorodiphenyl trichloroethane (DDT) and global malaria-control policy shifted toward domestic adulticide methods. Larval-control methods should now be re-prioritised for research, development, and implementation as an additional way to roll back malaria. (Department of Public Health and Epidemiology, Swiss Topical Institute, Basel, Switzerland. gerry.killeen@unibas.ch)
3) Roberts, D.R., E. Vanzie, M.J. Bangs, J.P. Grieco, H. Lenares, P. Hshieh, E. Rejmankova, S. Manguin, R.G. Andre, and J. Polanco. Role of residual spraying for malaria control in Belize. Journal of Vector Ecology. June, 2002. 27(1): 63-69.
PANNA summary: This study of the impact of reduced residual spraying in Belize found that it is associated with increases in cases of malaria. The authors suggest that spraying technique be improved and targeted to minimize costs and negative effects, but that its practice continue at a level above 134.6 houses per thousand people in Belize. This number was determined to be the threshold for Belize, above which malaria infection rates will not grow.
Abstract: We studied the impact of reduced residual spraying in Belize by developing a logistic regression model on relationships between numbers of houses sprayed (mostly with DDT) and numbers of malaria cases. We defined the “minimum effective house spray rate” (MEHSR) as the level of spraying that will prevent increases in malaria rates for a defined population. Under the total coverage approach (all houses sprayed), the MEHSR for Belize was 134.6. The model also showed that the odds for decreasing malaria is 1.086 for each increase of 10 houses sprayed per 1000 population. In further testing, highly significant and differential changes in malaria rates were documented for paired groups of years with house spray rates that were either above or below the MEHSR. Numbers of malaria cases since 1995 are used to show how stratification methods are used in Belize to spray fewer houses (at levels below the MEHSR of 134.6).
4) Kroeger, A., J. Ordonez-Gonzalez, and A.I. Avina. Malaria control reinvented: health sector reform and strategy development in Colombia. Tropical Medicine and International Health. May 2002, vol. 7 no. 5, pp. 450-458.
PANNA summary: In the 1990's, Colombia undertook one of the most complex health sector reform programs in Latin America, involving the decentralization of the vertical vector-borne disease control program. There were definite negative impacts from the loss of supervisory capacities that lead to a decrease in malaria control efforts over all, and also from economic limitations that weren't initially expected by reformers. Malaria rates increased over that period. However, the transformed system is stronger in certain ways and has not yet been exploited to its fullest potential, so there is some promise for success in the future.
Abstract: The consequences of health sector reforms on control of malaria were analysed using Colombia as an example. One of the most complex health sector reform programmes in Latin America took place in the 1990s; it included transferring the vertical vector-borne disease control (VBDC) programme into health systems at state and district levels. A series of studies was undertaken in 1998-2000 at the national level (Ministry of Health Study), at the state level (Departamento Study) and at the health district level (District Study) using formal and informal interviews among control staff and document analysis as data collection tools. A government-financed national training programme for VBDC staff - which included direct observation of control operations - was also used to analyse health workers' performance in the postreform period (longitudinal study). The results showed that some shortcomings of the old vertical system, such as the negative aspects of trade union activity, have not been overcome while some positive aspects of the old system, such as capacity building, operational planning and supervision have been lost. This has contributed to a decrease in control activity which, in turn, has been associated with more malaria cases. Malaria control had to be reinvented at a much larger scale than anticipated by the reformers caused by a whole series of problems: complex financing of public health interventions in the new system, massive staff reductions, the difficulty of gaining access to district and state budgets, redefining entire organizations and - in addition to the reforms - introducing alternative strategies based on insecticide-treated materials and the growth of areas of general insecurity in many parts of Colombia itself. However, positive signs in the transformed system include: the strengthening of central control staff (albeit insufficient in numbers) when transferred from the Ministry of Health to the National Institute of Health, the opportunities offered by the Basic Health Plan (PAB) for new planning initiatives and intersectoral co-operation and the integration of malaria diagnosis and treatment into the general health services (associated with a decrease of malaria mortality). The potentials of the new system have not yet been fully exploited: capacity building, communication and management skills need to be improved and it require guidance from the national level. (Liverpool School of Tropical Medicine, Liverpool, UK. a.kroeger@liverpool.ac.uk)
5) Zapping mosquitoes with biopesticides. Pesticides News 54. December 2001. http://www.pan-uk.org/pestnews/contents/pnindex.htm
PANNA summary: Biopesticides are not chemicals but organisms, in the case of this study they are the spores of a bacterium that effects mosquito larvae in their aquatic habitat, killing them within a few days of application. This study found that this particular biopesticide used in the malarial hotspots outside Nicaragua’s capital city was highly effective, reducing malaria cases dramatically when applied several times a year. The approach was cost effective, both because the biopesticide is cheaper than fenthion powder that the government had been using and because it needed to be applied much less often. Biopesticides represent an effective alternative to chemical insecticides that is safer for people and the environment, and potentially much less expensive.
Abstract: Mosquito control can be an expensive and hazardous process relying on highly toxic and persistent insecticides. Recent experiences in Central America show that biological control is effective, safer and cheaper than chemical control.
6) Singer, Burton and Caldas de Castro, Marcia. Agricultural Colonization and Malaria on the Amazon Frontier. Annals of the New York Academy of Science. December 2001, 954:184-222.
PANNA summary: This study shows that the high risk of malaria infection on the Amazonian frontier results from policies that have encouraged colonization in the region by millions of poor settlers from the northeast and south of Brazil. This mass migration and frontier expansion allow for malaria persistence through the following factors: poor drainage along rural roads that provides permanent breeding sites for mosquitoes, poor housing conditions, deforestation and expansion of cattle pasture, influx of temporary laborers with no natural immunity to the disease, deficiencies in the local health system, and low knowledge of the disease and how it is spread among migrants. Future migrations into these kinds of frontier lands anywhere in the world must be accompanied by cooperative agricultural extension and public health components if they are to avoid dire health and economic consequences.
Abstract: The purpose of this paper is to characterize the interrelationships between macropolitical, social and economic policies, human migration, agricultural development, and malaria transmission on the Amazon frontier. We focus our analysis on a recent colonization project, POLONOROESTE, in the state of Rondônia. Employing data from field surveys in 1985-1987 and 1995, we use spatial statistical methodologies linked to a geographical information system (GIS) to describe the patterns of human settlement in the area, the ecological transformations induced by forest clearance practices, and the manner in which these factors determine gradations of malaria risk. Our findings show that land use patterns, linked to social organization of the community and the structure of the physical environment, played a key role in promoting malaria transmission. In addition, the location of each occupied area is itself an important determinant of the pattern of malaria risk. Based on lessons learned from our spatial and temporal characterization of malaria risk, we propose policies for malaria mitigation in the Brazilian Amazon. (Office of Population Research, Princeton University, Princeton, New Jersey, USA)
7) Gusamo, R. d’A. Overview of malaria control in the Americas. Parassitologia 41: 355-60, 1999.
PANNA summary: In the malaria-endemic nations of the Americas, there has been a false perception that malaria can only be controlled by insecticide spraying, which can only be implemented by centralized institutions. This perception, along with the push for decentralization of health services in the region, has made implementation of WHO's Global Malaria Control Strategy was more difficult. There has been a recent switch in policy away from eradicating malaria and toward eliminating death and illness from the disease. Thus far it has been successful, with a 60% reduction in mortality due to malaria. A new strategy developed in Mexico is now being implemented which simultaneously applies anti-parasitic measures to human and vectorial reservoirs in regions of newly formed settlements on the outskirts of urban areas. This approach is within the budgets of most effected nations.
Abstract: The malaria endemic countries of the Americas have adopted in 1992 the WHO Global Malaria Control Strategy whose difficulties of implementation have been compounded to a major reform in the health sector, as the countries adjust to conform to financial scarcity and new economic policies. Most countries of the Region have reoriented its control program from eradication of malaria to the elimination of malaria mortality and morbidity. The Region has advanced towards these objectives having already reduced its mortality by 60% and is now in the final stages of applying new tools to control transmission and rapidly advance to reduce the incidence of malaria in the Americas. (Pan American Health Organization/World Health Organization, Washington, DC 20037, USA. gusmaore@paho.org)
8) Casas, M., J.L. Torres, D.N. Brown, M.H. Rodriguez, and J.L. Arrendondo-Jimenez. Selective and conventional house spraying of DDT and bendiocarb against Anopheles pseudopunctipennis in southern Mexico. Journal of the American Mosquito Control Association, 14(4):410-420, 1998.
PANNA summary: This study looked at mosquito behaviors in houses with two variables: 1) use of DDT or bendiocarb (another pesticide), and 2) was the whole wall covered with insecticide (conventional method), or only a band over the mosquitoes' preferred resting area (selective method). The study found that DDT was a more effective mosquito repellant than bendiocarb, and that the actual number of bites was substantially less in DDT-treated houses. It also found that though mosquitoes tended to rest for longer on the walls of houses that had been selectively sprayed, the actual number of bites was about the same as a house that had been conventionally sprayed. The authors recommend using selective spraying to improve cost effectiveness.
Abstract: Indoor feeding behaviors and mortalities of Anopheles pseudopunctipennis females were evaluated following contact with selective (bands covering mosquitoes' preferred resting areas) and full applications of DDT and bendiocarb on indoor sprayable surfaces. The DDT residues provoked strong avoidance behavior. To a lesser degree, mosquitoes were also repelled by bendiocarb-sprayed surfaces. Because of strong irritancy/repellency, unfed mosquitoes were driven outdoors in proportionally higher numbers. The resting time on selectively or fully DDT-sprayed huts was greatly reduced in comparison to bendiocarb-sprayed huts. Although unfed mosquitoes tended to rest on non-DDT-sprayed surfaces in the selectively treated hut, the man-biting rate was similar with both types of treatments. Unfed mosquitoes were repelled less from selectively bendiocarb-treated surfaces. Similar reductions in postfed resting times were observed on all surfaces suggesting that once fed, mosquitoes rested on sprayed surfaces for shorter intervals of time. Engorged mosquitoes had normal resting behavior (pre- and postspray) within the range of preferred resting heights in both DDT- and bendiocarb-sprayed huts, but the proportion of mosquitoes fed in the DDT-treated huts was lower. Selective spraying of walls was as effective as spraying the complete walls with both insecticides, but DDT was more effective in reducing mosquito-human contact. These studies show that by more effectively targeting vector behavior, a cost-effective alternative to traditional control techniques can be achieved. (Centro de Investigacion de Paludismo, Instituto Nacional de Salud Publica, Chiapas, Mexico)
9) Grieco, J.P., N.L. Achee, R.G. Andre, and D.R. Roberts. A comparison study of house entering and exiting behavior of Anopheles vestitipennis (Diptera: Culicidae) using experimental huts sprayed with DDT or deltamethrin in the southern district of Toledo, Belize, C. A. Journal of Vector Ecology 25(1):52-73.
PANNA summary: This study looked at how and when mosquitoes entered and exited houses in the Toledo district of Belize in unsprayed houses, houses sprayed with deltamethrin, and houses sprayed with DDT. Deltamethrin was repellant, leading to 66% fewer mosquitoes entering the house, and it shifted the mosquitoes’ peak house leaving time to five hours earlier than before the house was sprayed. DDT’s repellant effect was even more pronounced, with 97% fewer mosquitoes entering the hut at all, and thus the authors believe it is a more effective tool against malaria in this region.
Abstract: An investigation of the house entering and exiting behavior of Anopheles vestitipennis Dyar and Knab was undertaken in the Toledo District of Belize, Central America, between March and December of 1998. Three untreated experimental huts were either fitted with exit or entrance interception traps or used as a control for human landing collections. Human landing collections showed that An. vestitipennis exhibited a high level of biting activity shortly after sunset and continued biting at high levels throughout the night. Under unsprayed conditions, the use of exit and entrance interception traps demonstrated that doors, windows, and eaves were the primary mode of entry; whereas, cracks in the walls served a secondary role. The peak entrance time for An. vestitipennis occurred between 6:45 P.M. and 9:45 P.M. and a peak exit time occurred between 11:45 P.M. and 4:45 A.M. Additional trials were conducted after spraying one of the huts with DDT and another with deltamethrin. The excito-repellent properties of deltamethrin did not affect entrance times but did result in a peak exiting behavior that was five hours earlier than under pre-spray conditions. Deltamethrin also exhibited a repellency effect, showing 66% fewer An. vestitipennis entering the hut two weeks post-spray. DDT had an even more powerful repellency effect resulting in a 97% post-spray reduction of An. vestitipennis females entering the hut up to two weeks post-spray. The control hut showed only a 37% reduction in An. vestitipennis as compared to pre-spray conditions. (Department of Preventive Medicine/Biometrics, Uniformed Services University of the Health Sciences, Bethesda, MD 20814, USA)
10) Charlwood, J.D., W.D. Alecrim, N. Fe, J. Mangabeira, and V.J. Martins. A field trial with Lambda-cyhalothrin (ICON) for the intradomiciliary control of malaria transmitted by Anopheles darlingi root in Rhondonia, Brazil. Acta Tropica, 60(1995): 3-13, 1995.
PANNA summary: This field trial compared the effectiveness of residual indoor spraying of ICON and DDT in Rhondonia in 1987 and 1988 and found that ICON was more effective than DDT, with drops of as much as 76% in malaria cases in treated areas. ICON lasts longer than DDT, is cheaper, and appears more lethal to insects, killing and driving away insects during the study that DDT would have only irritated. Based on these results, the authors recommend ICON as a replacement for DDT in malaria control campaigns.
Abstract: A two stage field trial comparing the effects of Lambdacyhalothrin (ICON) and DDT when used as residual sprays on the inside surfaces of houses, was conducted in the Machadinho and Jaru areas of Rhondonia, Brazil, in 1987 and 1988. In 1987 houses along two 16 km contiguous stretches of a main and a side road were sprayed and the effects on malaria vectors monitored for the succeeding year. In the second stage approximately 55,000 houses in both districts were sprayed with ICON and the effect on malaria incidence measured by passive case detection. Of the eleven species of Anopheles caught in indoor and peridomiciliary collections A. darlingi was the commonest and is recognised as the most important vector in Brazil. ICON at either of two concentrations in bioassays killed more mosquitoes than DDT at each test from seven to twelve months after spraying. A rise in the number of A. darlingi collected eight months after spraying with DDT was not so marked in the ICON areas. Side effects of the insecticide were limited. The number of reported Plasmodium falciparum cases in the second phase declined 76% in Machadinho after spraying with ICON to 2851 cases. In Jaru there was a 28% reduction. The observed efficacy of the insecticide, its ready acceptance by the local populace, and its cost effectiveness make it a more useful insecticide for anti-malaria campaigns than DDT. (Liverpool School of Tropical Medicine, UK)
11) Gonzalez, Fernando Bejarano. The phasing out of DDT in Mexico. http://www.icps.it/english/bollettino/psn01/010205.htm
PANNA summary: Mexico has succeeded in both phasing out DDT and bringing down malaria rates in the country through a program of integrated vector management. Mexico applied over 4,000 tons of DDT a year in 1959, and implemented a complete ban in the year 2000. The integrated vector management strategy called "focalized treatment" was first used in the state of Oxaca, where farmers and environmental organizations were opposed to the spraying of DDT. The approach includes: identifying and classifying at-risk communities, reducing the parasite loads in those communities through 3-month intensive treatments with chlorine and primachine, complementary application of pyrethroids indoors and outdoors, and assessment of disease controls.
(no abstract available)