Content Posted in 2012. Needed Directions for Measurement in Work Settings, Mary L. 11th Biennial Symposium Program, Part 1, Textiles as Cutlural Expressions. 15th Annual Conference Program. Anopheles darlingi is one of the most important malaria vectors in the Americas. In this era of new tools and strategies for malaria and vector control it is essential to have knowledge on the ecology and behavior. Information and guidance. Results of Literature Search. Relevant papers dated back to 1984. Supplementary Table 1 (see Supplementary Material available on line at http:// shows the results of the search and the. Factors Contributing to Urban Malaria Transmission in Sub- Saharan Africa: A Systematic Review. Department of Medicine, Imperial College London, London W2 1. PG, UK2. MRC Centre for Outbreak Analysis & Modelling, Department of Infectious Disease Epidemiology, Imperial College London, London W2 1.
PG, UKCopyright . This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Sub- Saharan Africa suffers by far the greatest malaria burden worldwide and is currently undergoing a profound demographic change, with a growing proportion of its population moving to urban areas. Urbanisation is generally expected to reduce malaria transmission; however the disease still persists in African cities, in some cases at higher levels than in nearby rural areas. This paper aims to collate and analyse risk factors for urban malaria transmission throughout sub- Saharan Africa and to discuss their implications for control. A systematic search on malaria and urbanisation was carried out focusing on sub- Saharan Africa. Particular interest was taken in vector breeding sites in urban and periurban areas. Mosquito Ecology Field Sampling Methods Pdf DownloadA variety of urban vector breeding sites were catalogued, the majority of which were artificial, including urban agriculture, tyre tracks, and ditches. Natural breeding sites varied according to location. Low socioeconomic status was a significant risk factor for malaria, often present in peri- urban areas. A worrying trend was seen in the adaptation of malaria vector species to the urban environment. Urban malaria is highly focused and control programs should reflect this. As urbanisation continues and vector species adapt, continued monitoring and control of urban malaria in sub- Saharan Africa is essential. Background. Despite recent declines in Plasmodium falciparum malaria transmission, largely due to increased distribution of long- lasting insecticide- treated nets (LLINs) and a switch to artemisinin- based combination therapy (ACT) drugs, sub- Saharan Africa still suffers greatly from the disease. According to World Health Organization (WHO) estimates, in 2. Africa . At the same time, Africa’s demography is rapidly changing, with an increasing number of people moving to urban areas. In West Africa, the population growth rate for urban areas is estimated at 6. As Africa becomes increasingly urbanized, factors contributing to urban malaria will become more relevant. The general consensus is that urbanization will lead to decreased malaria transmission. One recent modelling study predicts a 5. It is thought that urbanization leads to improved infrastructure, better- quality “mosquito- proof” housing, increased access to healthcare, and a reduction in vector breeding sites. Malaria vector species are known to prefer clean water for breeding, which is difficult to come by in polluted urban areas, and the higher ratio of humans to mosquitoes is also thought to lead to a decreased human biting rate . Indeed, there are African cities experiencing entomological inoculation rates (EIRs) greater than 8. A variety of factors may contribute to this, including socioeconomic status, urban agricultural practices and poorly- monitored land use . Uncontrolled urban expansion can lead to increased malaria transmission as town planners are unable to keep up with sprawling city boundaries and rural practices, which are conducive to vector breeding sites and incorporated into the urban fringes. Furthermore, areas of low socioeconomic status, often at the periphery of cities, are at particular risk. Here, poor- quality housing, unpaved roads, and reduced access to healthcare provide little protection against the disease . Annual EIRs compiled across dozens of African cities show a strong tendency for transmission to increase in a gradient from urban to periurban to rural areas—in the most recent meta- analysis, the average EIRs were 1. However, urban malaria transmission varies according to a number of additional factors such as location (e. This paper aims to identify the important factors in urban malaria transmission in sub- Saharan Africa, to better understand their interactions, and to discuss their relevance to policy makers in an increasingly urbanized continent. Literature Search. A systematic search on the impact of urbanisation on malaria transmission in sub- Saharan Africa was carried out in April 2. EMBASE, HMIC, Medline, Maternity and Infant Care, Psycinfo, and Transport through the OVIDSP gateway from 1. The search was performed as follows: . Papers referring to Africa were therefore chosen manually. Inclusion Criteria. The above key words yielded a total of 1,2. The authors agreed that the articles included from the search should meet the following criteria: (i) description of malaria burden/transmission/control in urban settings; (ii) study location in sub- Saharan Africa; (iii) English- language abstract. The first named author scanned all articles by title, eliminating those that did not concern sub- Saharan Africa, leaving 3. A further 1. 78 abstracts were rejected that did not meet the inclusion criteria. Full texts of the remaining 1. Where relevance to the inclusion criteria was questioned, the second named author independently evaluated the article and consensus was quickly reached. Finally, 1. 04 English- language articles and nine foreign- language abstracts were identified as relevant to the topic. The literature selection process is summarized in Figure 1. Figure 1: Flow chart of study selection process. Results of Literature Search. Relevant papers dated back to 1. Supplementary Table 1 (see Supplementary Material available on line at http: //dx. The authors agreed on which topics to focus on before coding them for each paper. As this paper is largely qualitative, points of interest were noted for each paper and collated for comparative analyses. The number of papers that contributed information to each topic is summarized in Table 1, along with the location and year of publication. We found that a comparable number of studies addressed the role of the vector breeding sites in urban malaria transmission () as those addressing the role of geographic disparities (). For papers referring to vector breeding sites, we recorded the number of studies referring to specific sites and summarized these in Table 2. Many papers were synonymous in their findings, so were noted but not necessarily included in the discussion. Table 1: Summary of results by year, location, and number of citations. Table 2: Urban vector breeding sites by number of citations. Urban, Periurban and Rural Transmission. As mentioned in the background, dozens of African cities show a clear trend of increasing malaria transmission from urban to periurban to rural settings . For example, in Ouagadougou, Burkina Faso, the P. This is largely due to the fact that African cities tend to grow outwards with perimeters consisting of relatively underdeveloped, poorly serviced settlements . Recent migrants from rural areas tend to bring their rural practices with them, creating a multitude of vector breeding sites . However, it should be noted that this is not a universal trend. In Libreville, Gabon, malaria transmission was found to be the highest in the urban center (EIR of 8. EIR of 1. 3. 3 per person per year) as a consequence of slum- like conditions in the urban center being surrounded by more affluent periurban suburbs . In Cotonou, Benin, malaria prevalence was highest in an intermediate zone (Pf. PR among children aged 6–1. Pf. PR of 2. 6%) and periphery (Pf. PR of 2. 5%). This has been explained by the abundance of urban agriculture in the intermediate zone and a salty lagoon at the periphery making it less conducive to the primary malaria vector Anopheles gambiae . This shows that we should not confine our impression of urban malaria simply to urban centres, but we should also base it on an understanding of the underlying geography. Malaria Vectors. Malaria in humans results from infection by any of five species of Plasmodium transmitted by approximately 5. Anopheles. In sub- Saharan Africa, the majority of deaths are caused by P. These species are part of a larger species complex, An. The M form is better adapted to urban and dry environments and tends to reproduce alongside irrigated fields and permanent or semipermanent swamps. The S form is better adapted to rural and humid forest areas and prefers temporary pools and brick- made ravines . Another vector species, Anopheles funestus, also contributes to malaria transmission on the continent and thrives in dry and periurban environments . In a recent study in urban Libreville, Gabon . S form accounted for 9. M form accounted for 0. An. Interestingly, all collected species and sub- species of the An. Urban environments are less favourable for vector species, particularly An. Mosquito dispersal is also much more limited in urban areas due to the higher housing density . Natural Vector Breeding Sites and Environmental Factors. The heavy burden of malaria in rural Africa is testimony to the ability of natural breeding sites to sustain vector populations. Natural breeding sites, although less common in urban areas, are nevertheless present. Field studies suggest that anopheline larvae are most likely to be found in permanent, shallow, sunlit pools of water of perimeter greater than 1. Temporary pools are less favoured because they may not provide sufficient time for eggs to develop and emerge as adults. It has also been suggested that they are more likely to be disturbed by human activity . A high groundwater table is particularly conducive to breeding sites as the absence of surface runoff allows pools of stagnant water to develop . Of the natural vector breeding sites referred to in the literature search, the most common were ponds () and swamps (). Also mentioned were seepages, springs, and streams and, in one study, An. Coastal Environments.
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