Saving Lives, Buying Time Economics of Malaria Drugs in an Age of Resistance (2004) / Chapter Skim
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8 Malaria Control
8 Malaria Control
Pages 197-251
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The chapter concludes with a discussion of malaria control strategies, including national and regional policies and programs operating today. HISTORICAL OVERVIEW Historically, malaria's reach extended far beyond the tropics.
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Sub-Saharan Africa was always a special case. With the exception of a few pilot programs, no sustained malaria control efforts were ever mounted there (Greenwood and Mutabingwa, 2002)
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Case management -- which encompasses prompt access to health care, an accurate diagnosis, and effective treatment -- is the other cornerstone of malaria control. The current failure to control malaria with drugs often starts with a failure to deliver appropriate case management to many malaria sufferers, particularly at the periphery of health systems.
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INSECTICIDES AND INSECTICIDE RESISTANCE Insecticides in Public Health Immediately after World War II, DDT and other chlorinated hydrocarbon insecticides formed the mainstay of malaria control. DDT was initially developed as a public health insecticide prior to its widespread agricultural use and recognition as an environmental pollutant (Curtis and Lines, 2000)
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. DDT's long-term repellant, and contact irritant effects probably contribute as much or more than its direct insecticidal action in controlling malaria transmission (Roberts et al., 2000)
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. INSECTICIDE-TREATED BEDNETS AND INDOOR RESIDUAL SPRAYING History of ITNs More than two thousand years before Ronald Ross and Giovanni Battista Grassi showed that mosquitoes transmit malaria, human beings used nets to fend off night-biting insects.
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. Interest in insecticide-impregnated nets as a malaria control tool resurfaced in the late 1970s and early 1980s.
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The most recent group-randomized controlled trial of permethrintreated bednets conducted in western Kenya (Hawley et al., 2003a) was designed to assess ITN efficacy at an upper range of year-round transmission.
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. In an area of high perennial transmission in western Kenya, ITNs delayed the time to first infection in infants from 4.5 to 10.7 months (ter Kuile et al., 2003a)
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Pyrethrum was first used for indoor residual spraying (IRS) in southern Africa and India and later replaced by DDT after World War II.
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; a trial in Kisumu, Kenya, where IRS with fenitrothion reduced malaria transmission by 96 percent compared to baseline over 2 years (Payne et al., 1976) ; and the Garki project in northern Nigeria where IRS with propoxur also substantially decreased transmission and improved infant and child mortality (Molineaux, 1985)
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Al though the study did not focus on malaria-related morbidity and mortality to the same degree as would be likely today, its parasitemia data suggest that mortality and morbidity from malaria would have fallen dramatically in study villages during the 2-year period of integrated malaria control. Brian Greenwood, London School of Hygiene and Tropical Medicine
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. OTHER VECTOR CONTROL MEASURES Household and Community Measures In areas of high malaria transmission, prevalence of infection may vary significantly over relatively short distances.
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that affect the microepidemiology of malaria are house siting, screening and construction, proximity of animals to human dwellings, and use of mosquito deterrents such as repellants, aerosols, and fumigants. House Siting and Construction Despite the fact that anopheline mosquitoes can fly substantial distances, the proximity of houses or villages to a breeding site strongly influences malaria risk, especially where breeding sites are restricted.
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, shading of stream banks, and clearing of vegetation are naturalistic manipulations that proved beneficial in controlling certain vectors, primarily in India and southeast Asia. Although eclipsed by residual insecticides for several decades, many of these environmental methods of vector control are now back in vogue with strong WHO endorsement.
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This section reviews the role of treatment as a control measure capable of reducing malaria transmission, as well as past and present chemoprevention strategies in residents of malaria-endemic areas. (See Chapter 9 for more detailed information regarding antimalarial drugs, drug resistance, and treatment protocols.)
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MDA as a method of reducing malaria transmission gained momentum after the 8-aminoquinolones (of which primaquine is the leading prototype) were discovered.
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2003. Economic Evaluation of Recent Malaria Control Interventions in KwaZulu, South Africa: SEACAT Evaluation.
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across the three rural district hospitals that serve the Ingwavuma community. Despite KwaZulu Natal also carrying South Africa's high est burden of the HIV/AIDS epidemic, the total number of "all cause" hospital ad missions also was reduced following improved malaria control.
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Thus, medicated salt has no place in malaria control today. One MDA program that incorporated other control interventions was recently reported from the island of Aneityum, Vanuatu.
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Although rarely implemented on any scale until recently, WHO recommended that all pregnant women in areas of moderate or high malaria transmission receive weekly chemoprophylaxis with chloroquine during their second and third trimesters. Because of drug resistance, this policy no longer offers much benefit.
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Although medicated salt and the unrestricted use of chloroquine and pyrimethamine in the 1960s contributed to the initial emergence and spread of drug resistance (Payne, 1988) , there is little evidence to suggest that targeted chemoprophylaxis produces the same effect to any meaningful degree.
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Rapid diagnosis, both on an individual and a population level, also is an important tool in overall malaria control. This section reviews currently available methods of diagnosis, with emphasis on newer rapid tests that require relatively little technical expertise to perform.
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Ease, speed, and low cost are the advantages of presumptive diagnosis; disadvantages include overdiagnosis -- which contributes in turn to wasted drugs, adverse drug effects, and accelerating drug resistance -- as well as underdiagnosis of malaria. Since other common diseases -- acute lower respiratory tract infection in children, in particular-may mimic the signs and symptoms of malaria, clinical diagnosis also can result in missed diagnoses of other treatable conditions (Redd et al., 1992; Rey et al., 1996)
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is a modification of light microscopy which exploits the affinity of parasite nucleic acid for acridine orange, a fluorescent dye. This test was adapted for malaria diagnosis using patented microhematocrit tubes pre-coated with acridine orange and fitted with a plastic float that spreads the buffy coat (the white blood cell and parasite fraction of blood)
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In summary, when to introduce RDTs into areas of sub-Saharan Africa hyperendemic for falciparum malaria remains an open question. One perspective on the use of RDTs comes from Asia, where providing the means to diagnose and treat malaria on the village level has coincided with a dramatic fall in morbidity and mortality.
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. MALARIA VACCINES No malaria vaccine has yet entered routine use, and a safe and effective vaccine is at least another 10 years away (Greenwood and Alonso, 2002)
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, Mozambique) Malaria Vaccine Development Unit, Pvs25, AMA-1 Transmission National Institutes of Health, USA (protein)
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A comprehensive discussion of all malaria vaccines is beyond the scope of this report; however, certain basic concepts and prototype vaccines are covered below. For further details of specific vaccine antigens and strategies, readers are directed to several excellent published reviews (Moore et al., 2002; Carvalho et al., 2002; Mahanty et al., 2003; Moorthy et al., 2004)
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. Sexual-stage vaccines, rather than protecting vaccinated individuals, are meant to reduce malaria transmission, especially in combination with other control methods.
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Whether or not an imperfect malaria vaccine justifies use in a particular setting will depend upon its efficacy relative to other available control tools, its acceptability, and its cost. Pregnant women in malaria-endemic areas, especially primigravidae, have a special need for enhanced malaria protection because of malaria's damaging effects in pregnancy.
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. Another important factor that will influence whether a partially effective malaria vaccine is introduced into routine use will be its cost effectiveness relative to other malaria control measures, such as ITNs (Graves, 1998; Goodman et al., 1999)
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. INTEGRATED CONTROL PROGRAMS AND SPECIAL SETTINGS Past and Present Models Over recent years, several historical examples have been cited as evidence that malaria control could be achieved in endemic areas by combining environmental and human interventions.
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This success could, in turn, stimulate expanding eradication efforts using vector control and other integrated interventions. Epidemic Malaria Malaria epidemics generally occur in regions where transmission is low or absent most of the time and populations lack protective immunity, although epidemics also can strike higher-transmission areas when there is a breakdown in health or environmental services, increasing drug resistance, or recent immigration of nonimmune individuals (e.g., laborers coming to
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. For example, chloroquine resistance has been identified as a key factor in the resurgence of malaria on the Kericho tea estates in Kenya where climate, environment, human population, health care provision, and malaria control measures remained stable (Shanks et al., 2000)
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. Specifically, the Abuja target aims to identify, and respond to 60 percent of malaria epidemics in Africa within 2 weeks of onset and detection (WHO, 2001)
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It also should be given as promptly as possible, which poses a major logistical challenge. MALARIA CONTROL PROGRAMS AND DRUG POLICIES Malaria control cannot be a campaign; it should be a policy, a long-term programme.
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made at the WHO Ministerial Conference on Malaria in October 1992 issued this landmark avowal: "We commit ourselves and our countries to control malaria and will plan for malaria control as an essential component of national development." In reality, however, the final decades of the twentieth century witnessed a steady decline in malaria control as countries moved from large vertically run organizations focused on IRS and malaria eradication (admittedly, many such programs were flawed) to a new common denominator: "a village health worker with a jar of chloroquine tablets" (Personal communication, B
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Because many countries with growing resistance to first-, second-, and even third-line antimalarial drugs are burdened with debt and poorly financed health budgets, a change in antimalarial drug policy is economically daunting. The process of policy change can also be time consuming and involved.
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236 SAVING LIVES, BUYING TIME TABLE 8-4 Countries/Regions Using ACTs as First-Line Therapy for Uncomplicated Malaria Region/Country First-Line Treatment Africa Region Burundi AS+AQ Comoros AL South Africa (KwaZulu Natal) AL Zambia AL Zanzibar AS+AQ Western Pacific Region Cambodia AS(3d)
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There are increasing calls for information exchanges among neighboring countries about their respective malaria situations, malaria treatment policies, and approaches used to combat drug-resistant malaria. Recognizing that a regional approach offers a better platform for addressing malaria control problems that influence policy, several networks and initiatives have been established, most notably, the East African Network for Monitoring Antimalarial Treatments (EANMAT)
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2003b. Perceptions of bed nets and malaria prevention before and after a randomized controlled trial of permethrin-treated bed nets in western Kenya.
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1993. A malaria control trial using insecticide-treated bed nets and targeted chemoprophylaxis in a rural area of the Gambia, West Africa.
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1991. Morbidity and mortality at Pare-Taveta, Kenya and Tanzania, 1954-66: The effects of a period of malaria control.
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1994. Prospects for malaria control through the genetic manipulation of its vectors.
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1999. Cost-effectiveness of malaria control in sub Saharan Africa.
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2003a. Community-wide effects of permethrin-treated bed nets on child mortality and malaria morbidity in West ern Kenya.
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2002. Eradication of Anopheles gambiae from Brazil: Lessons for malaria control in Africa?
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1998. A controlled trial of lambda-cyhalothrin-impregnated bed nets and/or dapsone/pyrimethamine for malaria control in Sierra Leone.
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2003. Economic Evaluation of Recent Malaria Control Interventions in KwaZulu, Natal, South Africa: SEACAT Evaluation.
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2003. Efficacy of permethrin-treated bed nets in the prevention of mortality in young children in an area of high perennial malaria transmission in western Kenya.
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1991. Influence of deltamethrin treatment of bed nets on malaria transmission in the Kou Valley, Burkina Faso.
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2002a. Malaria control by re sidual insecticide spraying in Chingola and Chililabombwe, Copperbelt Province, Zam bia.
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2003a. Impact of permethrin treated bed nets on malaria, anemia, and growth in infants in an area of intense peren nial malaria transmission in western Kenya.
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Plan of Action for Malaria Control 1993-2000. Geneva: World Health Organization.
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