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Malaria Control (malaria + control)
Selected AbstractsImpact of Malaria Control on Perceptions of Tourists and Tourism Operators Concerning Malaria Prevalence in KwaZulu-Natal, 1999/2000 Versus 2002/2003JOURNAL OF TRAVEL MEDICINE, Issue 6 2007Victor L. Kovner No abstract is available for this article. [source] Role of medicines in malaria control and eliminationDRUG DEVELOPMENT RESEARCH, Issue 1 2010Marian Warsame Abstract Antimalarial medicines constitute important tools to cure and prevent malaria infections, thereby averting death and disability; their role in reducing the transmission of malaria is becoming increasingly important. Effective medicines that are currently available include artemisinin-based combination therapies (ACTs) for uncomplicated malaria, parenteral and rectal formulations of artemisinin derivatives and quinine injectables for severe malaria, and primaquine as an anti-relapse agent. These medicines are not optimal, however, owing to safety considerations in specific risk groups, complex regimens, and less than optimal formulations. The efficacy of antimalarial medicines including currently used ACTs is threatened by parasite resistance. Resistance to artemisinins has recently been identified at the Cambodia,Thailand border. Intermittent preventive treatment is constrained by the lack of a replacement for sulfadoxine-pyrimethamine. Despite increasing financial support to procure medicines, access to medicines by populations at risk of malaria, particularly in African countries, remains poor. This is largely due to weak health systems that are unable to deliver quality diagnostics and medicines through an efficient supply chain system, close at hand to the sick patient, especially in remote rural areas. Health systems are also challenged by incorrect prescribing practices in the informal and often unregulated private sector (an important provider of medicines for malaria) and the proliferation of counterfeit and substandard medicines. The provision of a more equitable access to life-saving medicines requires no less than a steady drug development pipeline for new medicines tailored to meet the challenging conditions in endemic countries, ideally single dose, highly effective against both disease and relapse-causing parasites and infective forms, extremely safe and with a long shelf life, and made available at affordable prices. Drug Dev Res 71: 4,11, 2010. © 2010 Wiley-Liss, Inc. [source] Towards evolution-proof malaria control with insecticidesEVOLUTIONARY APPLICATIONS (ELECTRONIC), Issue 4 2009Jacob C. Koella Abstract As many strategies to control malaria use insecticides against adult mosquitoes, control is undermined by the continual evolution of resistant mosquitoes. Here we suggest that using alternative insecticides, or conventional insecticides in alternative ways might enable effective control, but delay considerably or prevent the evolution of resistance. Our reasoning relies on an epidemiological and an evolutionary principle: (i) the epidemiology of malaria is strongly influenced by the life-span of mosquitoes, as most infected mosquitoes die before the malaria parasite has completed its development; and (ii) evolutionary pressure is strongest in young individuals, for selection on individuals that have completed most of their reproduction has little evolutionary effect. It follows from these principles, first, that insecticides that kill mosquitoes several days after exposure can delay considerably the evolution of resistance and, second, that the evolution of resistance against larvicides can actually benefit control, if it is associated with shorter life-span or reduced biting in adults. If a late-acting insecticide and a larvicide are combined, the evolution of resistance against larvicides can in some circumstances prevent the evolution of resistance against the more effective, late-acting insecticide, leading to sustainable, effective control. We discuss several potential options to create such insecticides, focussing on biopesticides. [source] ORIGINAL ARTICLE: Probability of emergence of antimalarial resistance in different stages of the parasite life cycleEVOLUTIONARY APPLICATIONS (ELECTRONIC), Issue 1 2009Wirichada Pongtavornpinyo Abstract Understanding the evolution of drug resistance in malaria is a central area of study at the intersection of evolution and medicine. Antimalarial drug resistance is a major threat to malaria control and directly related to trends in malaria attributable mortality. Artemisinin combination therapies (ACT) are now recommended worldwide as first line treatment for uncomplicated malaria, and losing them to resistance would be a disaster for malaria control. Understanding the emergence and spread of antimalarial drug resistance in the context of different scenarios of antimalarial drug use is essential for the development of strategies protecting ACTs. In this study, we review the basic mechanisms of resistance emergence and describe several simple equations that can be used to estimate the probabilities of de novo resistance mutations at three stages of the parasite life cycle: sporozoite, hepatic merozoite and asexual blood stages; we discuss the factors that affect parasite survival in a single host in the context of different levels of antimalarial drug use, immunity and parasitaemia. We show that in the absence of drug effects, and despite very different parasite numbers, the probability of resistance emerging at each stage is very low and similar in all stages (for example per-infection probability of 10,10,10,9 if the per-parasite chance of mutation is 10,10 per asexual division). However, under the selective pressure provided by antimalarial treatment and particularly in the presence of hyperparasitaemia, the probability of resistance emerging in the blood stage of the parasite can be approximately five orders of magnitude higher than in the absence of drugs. Detailed models built upon these basic methods should allow us to assess the relative probabilities of resistance emergence in the different phases of the parasite life cycle. [source] Comparison of three pyrethroid treatments of top-sheets for malaria control in emergencies: entomological and user acceptance studies in an Afghan refugee camp in PakistanMEDICAL AND VETERINARY ENTOMOLOGY, Issue 2 2002K. Graham Abstract Insecticide-treated bedding materials (sheets and blankets) could be protective against vectors of malaria and leishmaniasis , especially in complex emergencies, epidemics and natural disasters where people are more likely to sleep in exposed situations. Comparison of cotton top-sheets impregnated with different pyrethroids (permethrin 500 mg/m2, deltamethrin 25 mg/m2 or alphacypermethrin 25 mg/m2) for effectiveness against mosquitoes (Diptera: Culicidae) was undertaken in a refugee camp in Pakistan. Predominant species encountered were Anopheles stephensi Liston, An. pulcherrimus Theobald, An. nigerrimus Giles, Culex quinquefasciatus Say, Cx. tritaeniorhynchus Giles and other culicine mosquitoes. All three pyrethroid treatments performed significantly better than the untreated sheets in deterrence and killing of mosquitoes. No significant differences were found between the three insecticides tested in terms of entomological effect. Washing of the treated sheets greatly reduced their effectiveness. In a user acceptance study conducted among 88 families (divided into four groups), six families complained of irritation of the skin and mucous membranes. Of these reports, one was from the placebo group (using untreated sheets) and the other five (5/22 = 23%) from families using deltamethrin-treated sheets. All families allocated to permethrin and alphacypermethrin groups declared an appreciation for the intervention and reported no side-effects. Ten of the placebo group disliked the intervention, citing no prevention of mosquito biting as the reason. Side-effects associated with deltamethrin indicate that alphacypermethrin and permethrin are more appropriate first choice insecticides for treatment of sheets and blankets. [source] Cost-comparison of DDT and alternative insecticides for malaria controlMEDICAL AND VETERINARY ENTOMOLOGY, Issue 4 2000K. Walker Summary In anti-malaria operations the use of DDT for indoor residual spraying has declined substantially over the past 30 years, but this insecticide is still considered valuable for malaria control, mainly because of its low cost relative to alternative insecticides. Despite the development of resistance to DDT in some populations of malaria vector Anopheles mosquitoes (Diptera: Culicidae), DDT remains generally effective when used for house-spraying against most species of Anopheles, due to excitorepellency as well as insecticidal effects. A 1990 cost comparison by the World Health Organization (WHO) found DDT to be considerably less expensive than other insecticides, which cost 2 to 23 times more on the basis of cost per house per 6 months of control. To determine whether such a cost advantage still prevails for DDT, this paper compares recent price quotes from manufacturers and WHO suppliers for DDT and appropriate formulations of nine other insecticides (two carbamates, two organophosphates and five pyrethroids) commonly used for residual house-spraying in malaria control programmes. Based on these ,global' price quotes, detailed calculations show that DDT is still the least expensive insecticide on a cost per house basis, although the price appears to be rising as DDT production declines. At the same time, the prices of pyrethroids are declining, making some only slightly more expensive than DDT at low application dosages. Other costs, including operations (labour), transportation and human safety may also increase the price advantages of DDT and some pyrethroids vs. organophosphates and carbamates, although possible environmental impacts from DDT remain a concern. However, a global cost comparison may not realistically reflect local costs or effective application dosages at the country level. Recent data on insecticide prices paid by the health ministries of individual countries showed that prices of particular insecticides can vary substantially in the open market. Therefore, the most cost-effective insecticide in any given country or region must be determined on a case-by-case basis. Regional coordination of procurement of public health insecticides could improve access to affordable products. [source] Genetic structure of Anopheles gambiae (Diptera: Culicidae) in São Tomé and Príncipe (West Africa): implications for malaria controlMOLECULAR ECOLOGY, Issue 10 2002J. Pinto Abstract The impact of a vector eradication programme, conducted in the 1980s, on Anopheles gambiae populations from the islands of São Tomé and Príncipe, was evaluated by microsatellite DNA analysis. Significant genetic differentiation was observed within and between the two islands and between the islands and a population from Gabon, suggesting a degree of isolation between them. Large estimates of long-term Ne suggested that the control programme did not affect the effective population size of the vector. Heterozygosity tests were also not consistent with a recent bottleneck. [source] Worms and malaria: noisy nuisances and silent benefitsPARASITE IMMUNOLOGY, Issue 7 2002Mathieu Nacher Summary The burden of malaria mortality has been a major evolutionary influence on human immunity. The selection of the most successful immune responses against malaria has been in populations concomitantly infected by intestinal helminths. Animal models have shown that coinfections with helminths and protozoa in the same host elicit a range of antagonist and synergistic interactions. Recent findings suggest similar interactions take place between helminths, Plasmodium falciparum and humans. However, as the threat of HIV and tuberculosis becomes a major selective force, what used to be a successful ecological system may now prove detrimental. Nevertheless, the understanding of the ecological forces at play may expose new intervention targets for malaria control, and give a new perspective on our shortcomings against the deadliest of human parasites. [source] Humoral immune responses during a malaria vaccine trial in Tanzanian infantsPARASITE IMMUNOLOGY, Issue 9 2000Galindo The development of a malaria vaccine is a priority for improved and sustained malaria control. Optimal use of a vaccine in Africa will only be achieved if it can be delivered through the Expanded Programme of Immunization (EPI). We have completed a trial of the peptide vaccine SPf66 in Tanzanian infants, given alongside the EPI vaccines. This paper describes the humoral responses to SPf66 and the EPI vaccines. A total of 1207 infants were recruited into a two-arm, double-blind, individually randomized placebo-controlled trial of SPf66. The objectives of the trial were to determine the safety, immunogenicity and efficacy of SPf66 and to assess interactions with EPI vaccines when three doses of SPf66 were delivered alongside the EPI vaccines. Cross-sectional surveys were carried out to asses seroconversion rates to the EPI vaccines and the antibody response to SPf66 (NANP)50 and Plasmodium falciparum lysates. Seroconversion rates to EPI vaccines were high and no statistically significant differences in prevalence or titres were found between SPf66 and placebo recipients. IgG antibodies against SPf66 (NANP)50 and whole P. falciparum lysate were present in high titres in mothers of recruited children at the time of birth. Vaccination with SPf66 stimulated a good anti-SPf66 IgG response which declined to preimmunization levels by 2 years of age and which was not associated with protection against clinical malaria. The vaccine induced no IgG antibodies against (NANP)50 or P. falciparum lysates. SPf66 stimulated a humoral immune response when given to very young infants and did not interfere with seroconversion to EPI vaccines. The response to SPf66 was qualitatively different from that seen in older children, in whom SPf66 has been shown to be moderately efficacious. This difference raises concerns about the difficulties of immunizing very young infants who need to be targeted by antimalarial vaccination programs. [source] "Roll Back Malaria, Roll in Development"?POPULATION AND DEVELOPMENT REVIEW, Issue 1 2009Reassessing the Economic Burden of Malaria Recent efforts to mobilize support for malaria control have highlighted the economic burden of malaria and the value of malaria control for generating economic development. These claims have a long history. Beginning in the early twentieth century, they became the primary justification for malaria-control programs in the American South and in other parts of the globe, including British India. Economists conducted none of these studies. Following World War II and the development of new anti-malarial drugs and pesticides, including DDT, malaria control and eradication were increasingly presented as instruments for eliminating economic underdevelopment. By the 1960s, however, economists and demographers began to raise serious substantive and methodological questions about the basis of these claims. Of particular concern was the role of rapid population growth, resulting in part from the decline of malaria mortality, in undermining the short-term economic gains achieved through malaria control. Despite these concerns, malaria continues to be presented as an economic problem in the work of Jeffrey Sachs and others, justifying massive investments in malaria control. The methodological basis of these claims is examined. The paper concludes that while malaria takes a dreadful toll in human lives and causes significant economic losses for individuals, families, and some industries, the evidence linking malaria control to national economic growth remains unconvincing. In addition, the evidence suggests that there are potential costs to justifying malaria-eradication campaigns on macroeconomic grounds. [source] | ||||||||||||||||