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Community-Based Control of Malaria Vectors Using Bacillus thuringiensis var. Israelensis ( Bti) in Rwanda. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2022; 19:ijerph19116699. [PMID: 35682283 PMCID: PMC9180564 DOI: 10.3390/ijerph19116699] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/19/2022] [Revised: 05/19/2022] [Accepted: 05/25/2022] [Indexed: 01/27/2023]
Abstract
Larval source management (LSM) programs for control of malaria vectors are often vertically organized, while there is much potential for involving local communities in program implementation. To address this, we evaluated the entomological impact of community-based application of Bacillus thuringiensis var. israelensis (Bti) in a rice irrigation scheme in Ruhuha, Rwanda. A non-randomized trial with control compared a Bti implementation program that was supervised by the project team (ES) with a program that was led and carried out by local rice farming communities (CB). One other area served as a control to assess mosquito populations without Bti application. Entomological surveys were carried out every two weeks and assessed the presence and abundance of the larval, pupal, and adult stages of Anopheles mosquitoes. In ES, the per round reduction in Anopheles larval habitats was estimated at 49%. This reduction was less in CB (28%) and control (22%) although the per round reduction in CB was still significantly higher than in control. Pupal production was almost completely prevented from round 5 (out of 10) onwards in both CB (average habitat occupancy 0.43%) and ES intervention arms (average habitat occupancy 0.27%), whereas pupal occupancy rates were on average 12.8% from round 5 onwards in the control. Emergence of adult mosquitoes from rice fields was thus prevented although this was not directly noticeable in adult An. gambiae populations in houses nearby the rice fields. Together with our earlier work on the willingness to financially contribute to the LSM program and the high perceived safety and acceptance of the Bti product, the current study demonstrates that, in an environment with limited resources, communities could become more engaged in LSM program implementation and contribute directly to malaria vector control in their environment.
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Rulisa A, van Kempen L, Mutesa L, Hakizimana E, Ingabire CM, Kateera F, Koenraadt CJM, van Vugt M, van den Borne B. Willingness to Contribute to Bio-Larviciding in the Fight against Malaria: A Contingent Valuation Study among Rice Farmers in Rwanda. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2021; 18:11575. [PMID: 34770086 PMCID: PMC8583195 DOI: 10.3390/ijerph182111575] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Revised: 10/25/2021] [Accepted: 10/31/2021] [Indexed: 01/17/2023]
Abstract
There is broad consensus that successful and sustained larval source management (LSM) interventions, including bio-larviciding campaigns, require embeddedness in local community institutions. Ideally, these community structures should also be capable of mobilizing local resources to (co-)finance interventions. To date, farmer cooperatives, especially cooperatives of rice growers whose economic activity facilitates mosquito breeding, have remained under the radar in designing community-based bio-larviciding campaigns. This study explores the potential of rice farmer cooperatives in Bugesera district, Rwanda, to take up the aforementioned roles. To this purpose, we surveyed 320 randomly selected rice farmers who belonged to one of four rice cooperatives in the area and elicited their willingness-to-pay (WTP) for application of Bti, a popular bio-larvicide, in their rice paddies. Results from a (non-incentivized) bidding game procedure, which tested two alternative contribution schemes showed that financial contributions would be significantly different from zero and sufficient to carry a co-financing share of 15-25 per cent. A strong heterogeneity in mean WTP is revealed across cooperatives, in addition to variation among individual farmers, which needs to be anticipated when engaging farmer cooperatives in LSM.
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Affiliation(s)
- Alexis Rulisa
- Medical Research Centre Division, Rwanda Biomedical Centre, Kigali 7162, Rwanda;
- Department of Cultural Anthropology and Development Studies, Radboud University, 6525 Nijmegen, The Netherlands
| | - Luuk van Kempen
- Department of Cultural Anthropology and Development Studies, Radboud University, 6525 Nijmegen, The Netherlands
| | - Leon Mutesa
- Center for Human Genetics, College of Medicine and Health Sciences, University of Rwanda, Kigali 4285, Rwanda;
| | - Emmanuel Hakizimana
- Malaria and Other Parasitic Diseases Division, Rwanda Biomedical Center, Kigali 7162, Rwanda;
| | - Chantal M. Ingabire
- Medical Research Centre Division, Rwanda Biomedical Centre, Kigali 7162, Rwanda;
| | - Fredrick Kateera
- Academic Medical Center, Department of Infectious Diseases, University of Amsterdam, 1012 Amsterdam, The Netherlands;
| | | | - Michèle van Vugt
- Center for Tropical Medicine and Travel Medicine, Academic Medical Center, University of Amsterdam, 1012 Amsterdam, The Netherlands;
| | - Bart van den Borne
- Department of Health Education & Promotion, Maastricht University, 6211 Maastricht, The Netherlands;
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Doumbe-Belisse P, Kopya E, Ngadjeu CS, Sonhafouo-Chiana N, Talipouo A, Djamouko-Djonkam L, Awono-Ambene HP, Wondji CS, Njiokou F, Antonio-Nkondjio C. Urban malaria in sub-Saharan Africa: dynamic of the vectorial system and the entomological inoculation rate. Malar J 2021; 20:364. [PMID: 34493280 PMCID: PMC8424958 DOI: 10.1186/s12936-021-03891-z] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Accepted: 08/20/2021] [Indexed: 12/11/2022] Open
Abstract
Sub-Saharan Africa is registering one of the highest urban population growth across the world. It is estimated that over 75% of the population in this region will be living in urban settings by 2050. However, it is not known how this rapid urbanization will affect vector populations and disease transmission. The present study summarizes findings from studies conducted in urban settings between the 1970s and 2020 to assess the effects of urbanization on the entomological inoculation rate pattern and anopheline species distribution. Different online databases such as PubMed, ResearchGate, Google Scholar, Google were screened. A total of 90 publications were selected out of 1527. Besides, over 200 additional publications were consulted to collate information on anopheline breeding habitats and species distribution in urban settings. The study confirms high malaria transmission in rural compared to urban settings. The study also suggests that there had been an increase in malaria transmission in most cities after 2003, which could also be associated with an increase in sampling, resources and reporting. Species of the Anopheles gambiae complex were the predominant vectors in most urban settings. Anopheline larvae were reported to have adapted to different aquatic habitats. The study provides updated information on the distribution of the vector population and the dynamic of malaria transmission in urban settings. The study also highlights the need for implementing integrated control strategies in urban settings.
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Affiliation(s)
- P Doumbe-Belisse
- Institut de Recherche de Yaoundé (IRY), Organisation de Coordination Pour la Lutte Contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroun.,Faculty of Sciences, University of Yaoundé I, P.O. Box 337, Yaoundé, Cameroon
| | - E Kopya
- Institut de Recherche de Yaoundé (IRY), Organisation de Coordination Pour la Lutte Contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroun.,Faculty of Sciences, University of Yaoundé I, P.O. Box 337, Yaoundé, Cameroon
| | - C S Ngadjeu
- Institut de Recherche de Yaoundé (IRY), Organisation de Coordination Pour la Lutte Contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroun.,Faculty of Sciences, University of Yaoundé I, P.O. Box 337, Yaoundé, Cameroon
| | - N Sonhafouo-Chiana
- Institut de Recherche de Yaoundé (IRY), Organisation de Coordination Pour la Lutte Contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroun.,Faculty of Health Sciences, University of Buea, Cameroon, P.O. Box 63, Buea, Cameroon
| | - A Talipouo
- Institut de Recherche de Yaoundé (IRY), Organisation de Coordination Pour la Lutte Contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroun.,Faculty of Sciences, University of Yaoundé I, P.O. Box 337, Yaoundé, Cameroon
| | - L Djamouko-Djonkam
- Institut de Recherche de Yaoundé (IRY), Organisation de Coordination Pour la Lutte Contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroun.,Faculty of Sciences, University of Dschang Cameroon, P.O. Box 67, Dschang, Cameroon
| | - H P Awono-Ambene
- Institut de Recherche de Yaoundé (IRY), Organisation de Coordination Pour la Lutte Contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroun
| | - C S Wondji
- Vector Group Liverpool School of Tropical Medicine Pembroke Place, Liverpool, L3 5QA, UK
| | - F Njiokou
- Faculty of Sciences, University of Yaoundé I, P.O. Box 337, Yaoundé, Cameroon
| | - C Antonio-Nkondjio
- Institut de Recherche de Yaoundé (IRY), Organisation de Coordination Pour la Lutte Contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroun. .,Vector Group Liverpool School of Tropical Medicine Pembroke Place, Liverpool, L3 5QA, UK.
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Djègbè I, Zinsou M, Dovonou EF, Tchigossou G, Soglo M, Adéoti R, Gbaguidi B, Atoyebi S, Chandre F, Akogbéto M, Lines J, Djouaka R. Minimal tillage and intermittent flooding farming systems show a potential reduction in the proliferation of Anopheles mosquito larvae in a rice field in Malanville, Northern Benin. Malar J 2020; 19:333. [PMID: 32928223 PMCID: PMC7491134 DOI: 10.1186/s12936-020-03406-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Accepted: 09/04/2020] [Indexed: 12/05/2022] Open
Abstract
Background Irrigation systems have been identified as one of the factors promoting malaria disease around agricultural farms in sub-Saharan Africa. However, if improved water management strategy is adopted during rice cultivation, it may help to reduce malaria cases among human population living around rice fields. This study aimed to assess the impact of the different irrigation practices on malaria transmission, as well as to evaluate the water management system that will best mitigate malaria transmission in Malanville, Benin. Methods Knowledge, Attitude and Practice (KAP) study was conducted on 104 households staying on and around the rice fields in Malanville. The study focused on the frequency of mosquito bites and preventive measures against malaria as well as soil preparation and rice planting methods. Mosquito larvae density was assessed in different water management system: continuous flooding (CF) or intermittent flooding (IF), deep tillage (DT) or minimal tillage (MT) and normal levelling (NL) or abnormal levelling (AL) in an experimental hut set-up. Larvae were collected using dipping methods and their density was determined. Results Three tillage systems, which include the use of tiller, plow and hoe, were identified on the rice field. Continuous flooding was the only irrigation system used by farmers. Retrospective data from Malanville Health Centre revealed higher malaria cases during rice production season, which was also confirmed by field participants. The density of Anopheles larvae was reduced by 80.8%, 30.8% and 40.7% (P = 0.000) during transplanting, tillering and maturation periods, respectively with intermittent flooding compared to continuous flooding. In addition, a clear reduction of larva density was observed with both intermittent flooding systems applied to minimal tillage (MT + IF + NL) and intermittent flooding applied to deep tillage (DT + IF + AL), showing that intermittent flooding could reduce the abundance of malaria vector in rice fields. Conclusion Recommending intermittent flooding technology for rice cultivation may not only be useful for water management but could also be an intentional strategy to control mosquitoes vector-borne diseases around rice farms.
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Affiliation(s)
- Innocent Djègbè
- National University of Sciences, Technologies, Engineering and Mathematics, Ecole Normale Supérieure de Natitingou, BP 72, Natitingou, Benin.
| | - Merdie Zinsou
- Laboratoire d'Hydrologie Appliquée, University of Abomey-Calavi, Institut National de l'eau, BP 526, Cotonou, Benin.,International Institute of Tropical Agriculture, 08 BP 0932, Cotonou, Benin
| | - Edia Flavien Dovonou
- Laboratoire d'Hydrologie Appliquée, University of Abomey-Calavi, Institut National de l'eau, BP 526, Cotonou, Benin
| | | | - Murielle Soglo
- International Institute of Tropical Agriculture, 08 BP 0932, Cotonou, Benin
| | - Razack Adéoti
- International Institute of Tropical Agriculture, 08 BP 0932, Cotonou, Benin
| | - Brice Gbaguidi
- International Institute of Tropical Agriculture, 08 BP 0932, Cotonou, Benin
| | - Seun Atoyebi
- International Institute of Tropical Agriculture, 08 BP 0932, Cotonou, Benin
| | - Fabrice Chandre
- UMR IRD 224-CNRS 5290-Université de Montpellier. MIVEGEC. Maladies Infectieuses et Vecteurs : Ecologie, Génétique, Evolution et Contrôle, 911 Avenue Agropolis, BP 64501, 34394, Montpellier Cedex 5, France
| | - Martin Akogbéto
- Centre de Recherche Entomologique de Cotonou (CREC), 06 BP 2604, Cotonou, Benin
| | - Jo Lines
- London School of Hygiene and Tropical Medicine, London, UK
| | - Rousseau Djouaka
- International Institute of Tropical Agriculture, 08 BP 0932, Cotonou, Benin
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Rose S, Ali MF, Bakhsh K, Ashfaq M, Hassan S. Linking environment, malaria, and agricultural returns: a labor time use analysis at different stages of production using 3SLS. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2020; 27:19714-19723. [PMID: 32221829 DOI: 10.1007/s11356-020-08507-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Accepted: 03/18/2020] [Indexed: 06/10/2023]
Abstract
The present study was designed to investigate the effects of disease on time spent by family and hired labor on farm activities. The effect of illness on cost incurred on farm activities and revenue earned from agriculture has also been examined in detail. The reason behind choosing malaria is because of its strong association with the quality of surrounding environment especially in the case of farm workers who are compelled to work in the environmental conditions quite suitable for the transmission of malaria. The effects of health shocks due to malaria are segregated according to three stages of production: land preparation, field management, and harvesting stages. Simultaneous equation model was employed using cross-sectional data collected from 252 farm workers through a pre-tested questionnaire. Farmers' living environment was found to be contributing in the spread of disease. Results also show that malaria affects labor time at harvesting stage as it is more labor-intensive stage of production. We find that malaria significantly affects the health of farm workers and their families forcing farm families to substitute family labor with hired labor. Further, the cost incurred on cure of disease significantly adds to the cost on agricultural production. This consequently leads to a substantial reduction in revenue. The effect of the cost incurred on prevention and cure of disease was also found negative on revenue. The study suggests that, in order to make farmers more productive, there should be malaria interventions specifically targeting the health of farmers. It is also suggested that, for successful malaria interventions especially in irrigated areas, the magnitude of the disease on different stages of production should be given due consideration.
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Affiliation(s)
- Sobia Rose
- Punjab Economic Research Institute, Planning and Develoment Board, Government of Punjab, Lahore, Pakistan.
| | - Muhammad Faisal Ali
- Institute of Agricultural and Resource Economics, University of Agriculture, Faisalabad, Pakistan
| | - Khuda Bakhsh
- COMSATS University Islamabad, Vehari Campus, Islamabad, Pakistan
| | - Muhammad Ashfaq
- Institute of Agricultural and Resource Economics, University of Agriculture, Faisalabad, Pakistan
| | - Sarfraz Hassan
- Institute of Agricultural and Resource Economics, University of Agriculture, Faisalabad, Pakistan
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Rumisha SF, Shayo EH, Mboera LEG. Spatio-temporal prevalence of malaria and anaemia in relation to agro-ecosystems in Mvomero district, Tanzania. Malar J 2019; 18:228. [PMID: 31288840 PMCID: PMC6617584 DOI: 10.1186/s12936-019-2859-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Accepted: 07/01/2019] [Indexed: 11/29/2022] Open
Abstract
Background Agro-ecological systems have been associated with increased malaria intensity. This study determined association between different agro-ecological systems, prevalence of malaria parasitaemia and anaemia in Mvomero district, Tanzania. Methods The study was carried out in three agro-ecosystems namely, savannah, rice-irrigation, and sugarcane. Malaria and anaemia prevalence were measured in four seasons of a year. Villages were categorized according to environmental characteristics, proportion of water-shaded areas and agro-ecosystems. Mixed-effects logistic regression analysis was used to determine factors associated with malaria infection. Results A total of 7888 individuals were involved with the overall malaria prevalence of 34.4%. Plasmodium falciparum was the dominant (99.52%) malaria species. Malaria prevalence was highest (42.9%) in children of 10–15 years of age, and significantly low during dry and hot season. Of the infected individuals, 78.1% were from rice-irrigation, 18.7% savannah and 3.2% sugarcane ecosystem. Individuals living in villages with high levels of water-shaded areas had highest malaria risk. Over three-quarters (78.9%) of the individuals slept under a mosquito net, with the highest (88.5%) coverage among individuals in sugarcane ecosystem. On average 47.1% of the children were anaemic. Anaemia was more prevalent (60.5%) among individuals in the savannah than in the rice-irrigation (48.2%) or sugarcane communities (23%). Analysis indicated that ecosystems and levels of water-shaded area were highly correlated, and altered levels of malaria infection. Gender, age, mosquito net-use, and season were other significant determinants of P. falciparum infection. Males had higher odds than females (OR = 1.16, 95% CI 1.05, 1.29). The risk for children 6–9 years and older children (10–15 years) was over 50% and 24%, respectively, higher compared to young ones (0–5 years). Use of mosquito net reduced malaria risk by 26%. The risk of infection was higher during dry and cool season (OR = 1.92, 95 %CI 1.66, 2.23) compared to other seasons. Living in villages with high level of water-shaded areas increased the chances of getting malaria up to 15 times than living in drier areas. Similarly, infection odds increased when living in savannah and rice-irrigation ecosystems than in the sugarcane ecosystem. Conclusions Findings show significant variations in malaria prevalence between communities living in different agro-ecosystems within the same district. Local malaria control strategies should consider these variations and liaise with agricultural experts while designing interventions to maximize effectiveness.
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Affiliation(s)
- Susan F Rumisha
- National Institute for Medical Research, 3 Barack Obama Drive, P.O. Box 9653, Dar es Salaam, Tanzania.
| | - Elizabeth H Shayo
- National Institute for Medical Research, 3 Barack Obama Drive, P.O. Box 9653, Dar es Salaam, Tanzania
| | - Leonard E G Mboera
- National Institute for Medical Research, 3 Barack Obama Drive, P.O. Box 9653, Dar es Salaam, Tanzania.,SACIDS Foundation for One Health, Sokoine University of Agriculture, Chuo Kikuu, P.O. Box 3297, Morogoro, Tanzania
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Tandina F, Doumbo O, Yaro AS, Traoré SF, Parola P, Robert V. Mosquitoes (Diptera: Culicidae) and mosquito-borne diseases in Mali, West Africa. Parasit Vectors 2018; 11:467. [PMID: 30103823 PMCID: PMC6090629 DOI: 10.1186/s13071-018-3045-8] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2018] [Accepted: 08/01/2018] [Indexed: 11/16/2022] Open
Abstract
Mosquito-borne diseases cause major human diseases in almost every part of the world. In West Africa, and notably in Mali, vector control measures help reduce the impact of mosquito-borne diseases, although malaria remains a threat to both morbidity and mortality. The most recent overview article on mosquitoes in Mali was published in 1961, with a total of 88 species. Our present review focuses on mosquitoes of medical importance among which the Anopheles vectors of Plasmodium and filaria, as well as the Culex and Aedes vectors of arboviruses. It aims to provide a concise update of the literature on Culicidae, covering the ecological areas in which the species are found but also the transmitted pathogens and recent innovative tools for vector surveys. This review highlights the recent introduction of invasive mosquito species, including Aedes albopictus and Culex neavei. The comprehensive list of mosquito species currently recorded includes 106 species (28 species of the Anophelinae and 78 species of the Culicinae). There are probable gaps in our knowledge concerning mosquitoes of the subfamily Culicinae and northern half of Mali because most studies have been carried out on the genus Anopheles and have taken place in the southern part of the country. It is hoped that this review may be useful to decision makers responsible for vector control strategies and to researchers for future surveys on mosquitoes, particularly the vectors of emerging arboviruses.
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Affiliation(s)
- Fatalmoudou Tandina
- Aix Marseille Univ, IRD, AP-HM, SSA, VITROME, IHU-Méditerranée Infection, Marseille, France
- Department of Epidemiology of Parasitic Diseases, Malaria Research and Training Center, Faculty of Sciences and Techniques, University of Science, Techniques and Technologies of Bamako, Bamako, Mali
| | - Ogobara Doumbo
- Department of Epidemiology of Parasitic Diseases, Malaria Research and Training Center, Faculty of Sciences and Techniques, University of Science, Techniques and Technologies of Bamako, Bamako, Mali
| | - Alpha Seydou Yaro
- Department of Epidemiology of Parasitic Diseases, Malaria Research and Training Center, Faculty of Sciences and Techniques, University of Science, Techniques and Technologies of Bamako, Bamako, Mali
| | - Sékou F. Traoré
- Department of Epidemiology of Parasitic Diseases, Malaria Research and Training Center, Faculty of Sciences and Techniques, University of Science, Techniques and Technologies of Bamako, Bamako, Mali
| | - Philippe Parola
- Aix Marseille Univ, IRD, AP-HM, SSA, VITROME, IHU-Méditerranée Infection, Marseille, France
| | - Vincent Robert
- MIVEGEC Unit, IRD-CNRS-Univ. Montpellier, Montpellier, France
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Paleopathological Considerations on Malaria Infection in Korea before the 20th Century. BIOMED RESEARCH INTERNATIONAL 2018; 2018:8516785. [PMID: 29854798 PMCID: PMC5966694 DOI: 10.1155/2018/8516785] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/28/2017] [Accepted: 04/01/2018] [Indexed: 12/31/2022]
Abstract
Malaria, one of the deadliest diseases in human history, still infects many people worldwide. Among the species of the genus Plasmodium, P. vivax is commonly found in temperate-zone countries including South Korea. In this article, we first review the history of malarial infection in Korea by means of studies on Joseon documents and the related scientific data on the evolutionary history of P. vivax in Asia. According to the historical records, malarial infection was not unusual in pre-20th-century Korean society. We also found that certain behaviors of the Joseon people might have affected the host-vector-pathogen relationship, which could explain why malarial infection prevalence was so high in Korea at that time. In our review of genetic studies on P. vivax, we identified substantial geographic differentiation among continents and even between neighboring countries. Based on these, we were able to formulate a strategy for future analysis of ancient Plasmodium strains in Korea.
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Diakité NR, Guindo-Coulibaly N, Adja AM, Ouattara M, Coulibaly JT, Utzinger J, N'Goran EK. Spatial and temporal variation of malaria entomological parameters at the onset of a hydro-agricultural development in central Côte d'Ivoire. Malar J 2015; 14:340. [PMID: 26341670 PMCID: PMC4560863 DOI: 10.1186/s12936-015-0871-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Accepted: 08/25/2015] [Indexed: 11/23/2022] Open
Abstract
Background A deeper understanding of the ecology and small-scale heterogeneity of malaria transmission is essential for the design of effective prevention, control and elimination interventions. The spatial and temporal distribution of malaria vectors was investigated in five villages in close proximity to a hydro-agricultural system in Côte d’Ivoire over the course of construction and the early phase of irrigated rice farming. Methods The study was carried out in five villages (Raffierkro, N’Douakro, Ahougui, Kpokahankro, Koffikro) near Bouaké, central Côte d’Ivoire, between early 2007 and late 2009. In each village, mosquitoes were collected by human landing catches and identified morphologically at genus and species level, and entomological parameters were determined. Plasmodium infection was assessed by dissection and an enzyme-linked immunosorbent assay. Results A total of 19,404 mosquitoes belonging to the genus Anopheles were sampled during 328 human-night catches. Before the construction of the hydro-agricultural system, comparable densities of Anopheles gambiae were observed in all villages. In subsequent years, densities in Raffierkro and Ahougui were significantly higher than the other villages [Kruskal–Wallis (KW) test = 31.13, p < 0.001]. The density of Anopheles funestus in the five villages was comparable in the early stage of the project, while a high density was reported in Koffikro at the end (KW test = 11.91, p = 0.018). Transmission of Plasmodium falciparum is perennial in the study area. Over the course of the study, high entomological inoculation rates (EIRs) were found: 219–328 infectious bites per person per year with An. gambiae. For An. funestus considerably lower EIRs were observed (5.7–39.4). Changing patterns of An. gambiae were not correlated with malaria transmission. Conclusion In this study setting, located in the bioclimatic transition zone of Côte d’Ivoire, rice cultivation was not observed to increase malaria transmission. The entomological parameters recorded until the onset of rice-growing activities in a hydro-agricultural system presented considerable heterogeneity both in space and time; a strong increase of Anopheles mosquitoes was observed in two of the five villages located in close proximity to the dam and irrigated rice fields. Malaria still is a main public health problem in all villages that require adequate control measures.
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Affiliation(s)
- Nana R Diakité
- Unité de Formation et de Recherche Biosciences, Université Félix Houphouët-Boigny, 22 BP 522, Abidjan 22, Côte d'Ivoire.
| | - Négnorogo Guindo-Coulibaly
- Unité de Formation et de Recherche Biosciences, Université Félix Houphouët-Boigny, 22 BP 522, Abidjan 22, Côte d'Ivoire.
| | - Akré M Adja
- Unité de Formation et de Recherche Biosciences, Université Félix Houphouët-Boigny, 22 BP 522, Abidjan 22, Côte d'Ivoire.
| | - Mamadou Ouattara
- Unité de Formation et de Recherche Biosciences, Université Félix Houphouët-Boigny, 22 BP 522, Abidjan 22, Côte d'Ivoire.
| | - Jean T Coulibaly
- Unité de Formation et de Recherche Biosciences, Université Félix Houphouët-Boigny, 22 BP 522, Abidjan 22, Côte d'Ivoire. .,Département Environnement et Santé, Centre Suisse de Recherches Scientifiques en Côte d'Ivoire, 01 BP 1303, Abidjan 01, Côte d'Ivoire. .,Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, P.O. Box, 4002, Basel, Switzerland. .,University of Basel, P.O. Box, 4003, Basel, Switzerland.
| | - Jürg Utzinger
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, P.O. Box, 4002, Basel, Switzerland. .,University of Basel, P.O. Box, 4003, Basel, Switzerland.
| | - Eliézer K N'Goran
- Unité de Formation et de Recherche Biosciences, Université Félix Houphouët-Boigny, 22 BP 522, Abidjan 22, Côte d'Ivoire. .,Département Environnement et Santé, Centre Suisse de Recherches Scientifiques en Côte d'Ivoire, 01 BP 1303, Abidjan 01, Côte d'Ivoire.
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Ouattara AF, Dagnogo M, Constant EAV, Koné M, Raso G, Tanner M, Olliaro PL, Utzinger J, Koudou BG. Transmission of malaria in relation to distribution and coverage of long-lasting insecticidal nets in central Côte d'Ivoire. Malar J 2014; 13:109. [PMID: 24645751 PMCID: PMC4000051 DOI: 10.1186/1475-2875-13-109] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Accepted: 03/13/2014] [Indexed: 11/23/2022] Open
Abstract
Background The use of long-lasting insecticidal nets (LLINs) is an effective malaria control strategy. However, there are challenges to achieve high coverage, such as distribution sustainability, and coverage keep-up. This study assessed the effect of LLINs coverage and contextual factors on entomological indicators of malaria in rural Côte d’Ivoire. Methods The study was carried out between July 2009 and May 2012 in three villages (Bozi, N’Dakonankro and Yoho) of central Côte d’Ivoire. In Bozi and Yoho, LLINs were distributed free of charge by the national malaria control programme in 2008. In Bozi, an additional distribution was carried out in May 2011. No specific interventions were done in N’Dakonankro. Entomological surveys were conducted in July 2009 and July 2010 (baseline), and in August and November 2011 and in February 2012. Frequency of circumsporozoite protein was determined using an enzyme-linked immunosorbent assay. Regression models were employed to assess the impact of LLINs and changing patterns of irrigated rice farming on entomological parameters, and to determine associations with LLINs coverage and other contextual factors. Results In Bozi, high proportion of LLIN usage was observed (95-100%). After six months, 95% of LLINs were washed at least once and 79% were washed up to three times within one year. Anopheles gambiae was the predominant malaria vector (66.6% of all mosquitoes caught). From 2009 to 2012, in N’Dakonankro, the mean annual entomological inoculation rate (EIR) increased significantly from 116.8 infectious bites/human/year (ib/h/y) to 408.8 ib/h/y, while in the intervention villages, the EIR decreased significantly from 514.6 ib/h/y to 62.0 ib/h/y (Bozi) and from 83.9 ib/h/y to 25.5 ib/h/y (Yoho). The risk of an infectious bite over the three-year period was significantly lower in the intervention villages compared to the control village (p <0.001). Conclusion High coverage and sensitization of households to use LLINs through regular visits (particularly in Bozi) and abandoning irrigated rice farming (in Yoho) resulted in highly significant reductions of EIR. The national malaria control programme should consider household sensitization and education campaigns and other contextual factors to maximize the benefit of LLINs.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Benjamin G Koudou
- Centre Suisse de Recherches Scientifiques en Côte d'Ivoire, 01 BP 1303, Abidjan 01, Côte d'Ivoire.
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11
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Muriu SM, Coulson T, Mbogo CM, Godfray HCJ. Larval density dependence in Anopheles gambiae s.s., the major African vector of malaria. J Anim Ecol 2013; 82:166-74. [PMID: 23163565 PMCID: PMC5373432 DOI: 10.1111/1365-2656.12002] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2012] [Accepted: 09/04/2012] [Indexed: 12/01/2022]
Abstract
Anopheles gambiae sensu stricto is the most important vector of malaria in Africa although relatively little is known about the density-dependent processes determining its population size. Mosquito larval density was manipulated under semi-natural conditions using artificial larval breeding sites placed in the field in coastal Kenya; two experiments were conducted: one manipulating the density of a single cohort of larvae across a range of densities and the other employing fewer densities but with the treatments crossed with four treatments manipulating predator access. In the first experiment, larval survival, development rate and the size of the adult mosquito all decreased with larval density (controlling for block effects between 23% and 31% of the variance in the data could be explained by density). In the second experiment, the effects of predator manipulation were not significant, but again we observed strong density dependence in larval survival (explaining 30% of the variance). The results are compared with laboratory studies of A. gambiae larval competition and the few other studies conducted in the field, and the consequences for malaria control are discussed.
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Affiliation(s)
- Simon M Muriu
- Department of Entomology, KEMRI-Wellcome Trust Programme, P.O. Box 230, Kilifi, Kenya.
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12
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Development of environmental tools for anopheline larval control. Parasit Vectors 2011; 4:130. [PMID: 21733150 PMCID: PMC3143094 DOI: 10.1186/1756-3305-4-130] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2011] [Accepted: 07/06/2011] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Malaria mosquitoes spend a considerable part of their life in the aquatic stage, rendering them vulnerable to interventions directed to aquatic habitats. Recent successes of mosquito larval control have been reported using environmental and biological tools. Here, we report the effects of shading by plants and biological control agents on the development and survival of anopheline and culicine mosquito larvae in man-made natural habitats in western Kenya. Trials consisted of environmental manipulation using locally available plants, the introduction of predatory fish and/or the use of Bacillus thuringiensis var. israelensis (Bti) in various combinations. RESULTS Man-made habitats provided with shade from different crop species produced significantly fewer larvae than those without shade especially for the malaria vector Anopheles gambiae. Larval control of the African malaria mosquito An. gambiae and other mosquito species was effective in habitats where both predatory fish and Bti were applied, than where the two biological control agents were administered independently. CONCLUSION We conclude that integration of environmental management techniques using shade-providing plants and predatory fish and/or Bti are effective and sustainable tools for the control of malaria and other mosquito-borne disease vectors.
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Bukhari T, Takken W, Githeko AK, Koenraadt CJM. Efficacy of aquatain, a monomolecular film, for the control of malaria vectors in rice paddies. PLoS One 2011; 6:e21713. [PMID: 21738774 PMCID: PMC3126853 DOI: 10.1371/journal.pone.0021713] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2011] [Accepted: 06/07/2011] [Indexed: 11/26/2022] Open
Abstract
Background Rice paddies harbour a large variety of organisms including larvae of malaria mosquitoes. These paddies are challenging for mosquito control because their large size, slurry and vegetation make it difficult to effectively apply a control agent. Aquatain, a monomolecular surface film, can be considered a suitable mosquito control agent for such breeding habitats due to its physical properties. The properties allow Aquatain to self-spread over a water surface and affect multiple stages of the mosquito life cycle. Methodology/Principal Findings A trial based on a pre-test/post-test control group design evaluated the potential of Aquatain as a mosquito control agent at Ahero rice irrigation scheme in Kenya. After Aquatain application at a dose of 2 ml/m2 on rice paddies, early stage anopheline larvae were reduced by 36%, and late stage anopheline larvae by 16%. However, even at a lower dose of 1 ml/m2 there was a 93.2% reduction in emergence of anopheline adults and 69.5% reduction in emergence of culicine adults. No pupation was observed in treated buckets that were part of a field bio-assay carried out parallel to the trial. Aquatain application saved nearly 1.7 L of water in six days from a water surface of 0.2 m2 under field conditions. Aquatain had no negative effect on rice plants as well as on a variety of non-target organisms, except backswimmers. Conclusions/Significance We demonstrated that Aquatain is an effective agent for the control of anopheline and culicine mosquitoes in irrigated rice paddies. The agent reduced densities of aquatic larval stages and, more importantly, strongly impacted the emergence of adult mosquitoes. Aquatain also reduced water loss due to evaporation. No negative impacts were found on either abundance of non-target organisms, or growth and development of rice plants. Aquatain, therefore, appears a suitable mosquito control tool for use in rice agro-ecosystems.
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Affiliation(s)
- Tullu Bukhari
- Laboratory of Entomology, Wageningen University and Research Centre, Wageningen, The Netherlands.
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Sinka ME, Bangs MJ, Manguin S, Coetzee M, Mbogo CM, Hemingway J, Patil AP, Temperley WH, Gething PW, Kabaria CW, Okara RM, Van Boeckel T, Godfray HCJ, Harbach RE, Hay SI. The dominant Anopheles vectors of human malaria in Africa, Europe and the Middle East: occurrence data, distribution maps and bionomic précis. Parasit Vectors 2010; 3:117. [PMID: 21129198 PMCID: PMC3016360 DOI: 10.1186/1756-3305-3-117] [Citation(s) in RCA: 406] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2010] [Accepted: 12/03/2010] [Indexed: 11/10/2022] Open
Abstract
Background This is the second in a series of three articles documenting the geographical distribution of 41 dominant vector species (DVS) of human malaria. The first paper addressed the DVS of the Americas and the third will consider those of the Asian Pacific Region. Here, the DVS of Africa, Europe and the Middle East are discussed. The continent of Africa experiences the bulk of the global malaria burden due in part to the presence of the An. gambiae complex. Anopheles gambiae is one of four DVS within the An. gambiae complex, the others being An. arabiensis and the coastal An. merus and An. melas. There are a further three, highly anthropophilic DVS in Africa, An. funestus, An. moucheti and An. nili. Conversely, across Europe and the Middle East, malaria transmission is low and frequently absent, despite the presence of six DVS. To help control malaria in Africa and the Middle East, or to identify the risk of its re-emergence in Europe, the contemporary distribution and bionomics of the relevant DVS are needed. Results A contemporary database of occurrence data, compiled from the formal literature and other relevant resources, resulted in the collation of information for seven DVS from 44 countries in Africa containing 4234 geo-referenced, independent sites. In Europe and the Middle East, six DVS were identified from 2784 geo-referenced sites across 49 countries. These occurrence data were combined with expert opinion ranges and a suite of environmental and climatic variables of relevance to anopheline ecology to produce predictive distribution maps using the Boosted Regression Tree (BRT) method. Conclusions The predicted geographic extent for the following DVS (or species/suspected species complex*) is provided for Africa: Anopheles (Cellia) arabiensis, An. (Cel.) funestus*, An. (Cel.) gambiae, An. (Cel.) melas, An. (Cel.) merus, An. (Cel.) moucheti and An. (Cel.) nili*, and in the European and Middle Eastern Region: An. (Anopheles) atroparvus, An. (Ano.) labranchiae, An. (Ano.) messeae, An. (Ano.) sacharovi, An. (Cel.) sergentii and An. (Cel.) superpictus*. These maps are presented alongside a bionomics summary for each species relevant to its control.
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Affiliation(s)
- Marianne E Sinka
- Spatial Ecology and Epidemiology Group, Tinbergen Building, Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK.
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15
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Mwangangi JM, Shililu J, Muturi EJ, Muriu S, Jacob B, Kabiru EW, Mbogo CM, Githure J, Novak RJ. Anopheles larval abundance and diversity in three rice agro-village complexes Mwea irrigation scheme, central Kenya. Malar J 2010; 9:228. [PMID: 20691120 PMCID: PMC2927610 DOI: 10.1186/1475-2875-9-228] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2010] [Accepted: 08/09/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The diversity and abundance of Anopheles larvae has significant influence on the resulting adult mosquito population and hence the dynamics of malaria transmission. Studies were conducted to examine larval habitat dynamics and ecological factors affecting survivorship of aquatic stages of malaria vectors in three agro-ecological settings in Mwea, Kenya. METHODS Three villages were selected based on rice husbandry and water management practices. Aquatic habitats in the 3 villages representing planned rice cultivation (Mbui Njeru), unplanned rice cultivation (Kiamachiri) and non-irrigated (Murinduko) agro-ecosystems were sampled every 2 weeks to generate stage-specific estimates of mosquito larval densities, relative abundance and diversity. Records of distance to the nearest homestead, vegetation coverage, surface debris, turbidity, habitat stability, habitat type, rice growth stage, number of rice tillers and percent Azolla cover were taken for each habitat. RESULTS Captures of early, late instars and pupae accounted for 78.2%, 10.9% and 10.8% of the total Anopheles immatures sampled (n = 29,252), respectively. There were significant differences in larval abundance between 3 agro-ecosystems. The village with 'planned' rice cultivation had relatively lower Anopheles larval densities compared to the villages where 'unplanned' or non-irrigated. Similarly, species composition and richness was higher in the two villages with either 'unplanned' or limited rice cultivation, an indication of the importance of land use patterns on diversity of larval habitat types. Rice fields and associated canals were the most productive habitat types while water pools and puddles were important for short periods during the rainy season. Multiple logistic regression analysis showed that presence of other invertebrates, percentage Azolla cover, distance to nearest homestead, depth and water turbidity were the best predictors for Anopheles mosquito larval abundance. CONCLUSION These results suggest that agricultural practices have significant influence on mosquito species diversity and abundance and that certain habitat characteristics favor production of malaria vectors. These factors should be considered when implementing larval control strategies which should be targeted based on habitat productivity and water management.
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Affiliation(s)
- Joseph M Mwangangi
- Kenya Medical Research Institute, Centre for Geographic Medicine Research-Coast, PO Box 428, Kilifi 80108, Kenya.
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Chaves LF, Koenraadt CJM. Climate change and highland malaria: fresh air for a hot debate. QUARTERLY REVIEW OF BIOLOGY 2010; 85:27-55. [PMID: 20337259 DOI: 10.1086/650284] [Citation(s) in RCA: 146] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
In recent decades, malaria has become established in zones at the margin of its previous distribution, especially in the highlands of East Africa. Studies in this region have sparked a heated debate over the importance of climate change in the territorial expansion of malaria, where positions range from its neglect to the reification of correlations as causes. Here, we review studies supporting and rebutting the role of climatic change as a driving force for highland invasion by malaria. We assessed the conclusions from both sides of the argument and found that evidence for the role of climate in these dynamics is robust. However, we also argue that over-emphasizing the importance of climate is misleading for setting a research agenda, even one which attempts to understand climate change impacts on emerging malaria patterns. We review alternative drivers for the emergence of this disease and highlight the problems still calling for research if the multidimensional nature of malaria is to be adequately tackled. We also contextualize highland malaria as an ongoing evolutionary process. Finally, we present Schmalhausen's law, which explains the lack of resilience in stressed systems, as a biological principle that unifies the importance of climatic and other environmental factors in driving malaria patterns across different spatio-temporal scales.
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Jarju LBS, Fillinger U, Green C, Louca V, Majambere S, Lindsay SW. Agriculture and the promotion of insect pests: rice cultivation in river floodplains and malaria vectors in The Gambia. Malar J 2009; 8:170. [PMID: 19635125 PMCID: PMC2734858 DOI: 10.1186/1475-2875-8-170] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2009] [Accepted: 07/27/2009] [Indexed: 12/03/2022] Open
Abstract
BACKGROUND Anthropogenic modification of natural habitats can create conditions in which pest species associated with humans can thrive. In order to mitigate for these changes, it is necessary to determine which aspects of human management are associated with the promotion of those pests. Anopheles gambiae, the main Africa malaria vector, often breeds in rice fields. Here the impact of the ancient practice of 'swamp rice' cultivation, on the floodplains of the Gambia River, on the production of anopheline mosquitoes was investigated. METHODS Routine surveys were carried out along 500 m transects crossing rice fields from the landward edge of the floodplains to the river during the 2006 rainy season. Aquatic invertebrates were sampled using area samplers and emergence traps and fish sampled using nets. Semi-field experiments were used to investigate whether nutrients used for swamp rice cultivation affected mosquito larval abundance. RESULTS At the beginning of the rainy season rice is grown on the landward edge of the floodplain; the first area to flood with fresh water and one rich in cattle dung. Later, rice plants are transplanted close to the river, the last area to dry out on the floodplain. Nearly all larval and adult stages of malaria vectors were collected 0-100 m from the landward edge of the floodplains, where immature rice plants were grown. These paddies contained stagnant freshwater with high quantities of cattle faeces. Semi-field studies demonstrated that cattle faeces nearly doubled the number of anopheline larvae compared with untreated water. CONCLUSION Swamp rice cultivation creates ideal breeding sites for malaria vectors. However, only those close to the landward edge harboured vectors. These sites were productive since they were large areas of standing freshwater, rich in nutrients, protected from fish, and situated close to human habitation, where egg-laying mosquitoes from the villages had short distances to fly. The traditional practice of 'swamp rice' cultivation uses different bodies of water on the floodplains to cultivate rice during the rainy season. A consequence of this cultivation is the provizion of ideal conditions for malaria vectors to thrive. As the demand for locally-produced rice grows, increased rice farming will generate great numbers of vectors; emphasizing the need to protect local communities against malaria.
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Affiliation(s)
| | - Ulrike Fillinger
- Disease Control & Vector Biology Unit, London School of Hygiene and Tropical Medicine, London, UK
| | - Clare Green
- School of Biological and Biomedical Sciences, Durham University, Durham, UK
| | - Vasilis Louca
- School of Biological and Biomedical Sciences, Durham University, Durham, UK
| | | | - Steven W Lindsay
- School of Biological and Biomedical Sciences, Durham University, Durham, UK
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Jardine A, Cook A, Weinstein P. The utility of mosquito-borne disease as an environmental monitoring tool in tropical ecosystems. JOURNAL OF ENVIRONMENTAL MONITORING : JEM 2008; 10:1409-14. [PMID: 19037481 DOI: 10.1039/b806520a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The intrinsic link between ecosystem health and human health has been firmly established in the literature and has given rise to the development of new multidisciplinary fields of research such as medical geology. An important practical implication of the ecosystem health approach is the utility of human disease outbreaks as indicators of underlying ecosystem disruption. The use of such a bioindicator is particularly relevant in developing countries where monitoring of traditional environmental and ecological indicators is not routinely undertaken. Mosquito-borne diseases appear to have good potential as bioindicators in tropical regions because the burden of disease is high, the disease ecology has a strong environmental component and intensive surveillance systems are well established. Evidence is reviewed regarding the utility of mosquito-borne disease to detect a range of ecosystem insults including: hydro-geological disruption in soil-water systems (e.g. secondary soil salinisation and waterlogging); escalating agricultural intensification; deforestation; and urbanisation. The evidence suggests that overall, mosquito-borne disease is a specific but insensitive indicator, because human modification of natural ecosystems does not always result in increases in disease incidence and can, in some cases, lead to reductions. Nevertheless, mosquito-borne disease remain useful as bioindicators if utilised as a complement to traditional environmental variables in identifying ecological disturbances; they can then assist in directing interventions that are concurrently beneficial to both human health and ecosystem health.
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Affiliation(s)
- Andrew Jardine
- School of Population Health, The University of Western Australia, 35 Stirling Highway, Crawley, Western Australia, Australia.
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Meide L, Xuezhong W, Tongyan Z, Du Z, Yande D, Baolin L. Analysis of the relationship between density and dominance of Anopheles minimus (Diptera: Culicidae) with environmental parameters in southern Yunnan Province, Peoples Republic of China. JOURNAL OF MEDICAL ENTOMOLOGY 2008; 45:1007-1010. [PMID: 19058623 DOI: 10.1603/0022-2585(2008)45[1007:aotrbd]2.0.co;2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The association of environmental factors with fluctuations in the density of the malaria vector Anopheles minimus (Theobald, 1901) was analyzed in Longtang and Dongfanghong, two villages in southern Yunnan Province, Peoples Republic of China. The distance of trap locations to rice fields and the distance from trap locations to rivulets were negatively correlated to the density of An. minimus. The length of a rivulet within a 1-km buffer around a trap location was positively correlated to the density of An. minimus, whereas the rice field area within a 1-km buffer of a trap location was negatively correlated to An. minimus dominance, but the length of a rivulet within a 1-km buffer around a trap location and the distance of trap locations to rice fields were positively correlated to An. minimus dominance. Linear models relating the density and dominance of An. minimus at trap sites in relation to environmental parameters are described. These results could help in the design of malaria control strategies.
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Affiliation(s)
- Liu Meide
- State Key Laboratory of Pathogen and Biosecurity, Institute of Microbiology and Epidemiology, Beijing 100071, China
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Muriu SM, Muturi EJ, Shililu JI, Mbogo CM, Mwangangi JM, Jacob BG, Irungu LW, Mukabana RW, Githure JI, Novak RJ. Host choice and multiple blood feeding behaviour of malaria vectors and other anophelines in Mwea rice scheme, Kenya. Malar J 2008; 7:43. [PMID: 18312667 PMCID: PMC2291060 DOI: 10.1186/1475-2875-7-43] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2007] [Accepted: 02/29/2008] [Indexed: 11/10/2022] Open
Abstract
Background Studies were conducted between April 2004 and February 2006 to determine the blood-feeding pattern of Anopheles mosquitoes in Mwea Kenya. Methods Samples were collected indoors by pyrethrum spay catch and outdoors by Centers for Disease Control light traps and processed for blood meal analysis by an Enzyme-linked Immunosorbent Assay. Results A total of 3,333 blood-fed Anopheles mosquitoes representing four Anopheles species were collected and 2,796 of the samples were assayed, with Anopheles arabiensis comprising 76.2% (n = 2,542) followed in decreasing order by Anopheles coustani 8.9% (n = 297), Anopheles pharoensis 8.2% (n = 272) and Anopheles funestus 6.7% (n = 222). All mosquito species had a high preference for bovine (range 56.3–71.4%) over human (range 1.1–23.9%) or goat (0.1–2.2%) blood meals. Some individuals from all the four species were found to contain mixed blood meals. The bovine blood index (BBI) for An. arabiensis was significantly higher for populations collected indoors (71.8%), than populations collected outdoors (41.3%), but the human blood index (HBI) did not differ significantly between the two populations. In contrast, BBI for indoor collected An. funestus (51.4%) was significantly lower than for outdoor collected populations (78.0%) and the HBI was significantly higher indoors (28.7%) than outdoors (2.4%). Anthropophily of An. funestus was lowest within the rice scheme, moderate in unplanned rice agro-ecosystem, and highest within the non-irrigated agro-ecosystem. Anthropophily of An. arabiensis was significantly higher in the non-irrigated agro-ecosystem than in the other agro-ecosystems. Conclusion These findings suggest that rice cultivation has an effect on host choice by Anopheles mosquitoes. The study further indicate that zooprophylaxis may be a potential strategy for malaria control, but there is need to assess how domestic animals may influence arboviruses epidemiology before adapting the strategy.
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Affiliation(s)
- Simon M Muriu
- Human Health Division, International Centre of Insect Physiology and Ecology P.O. Box 30772-00100, Kenya, Africa.
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Moffett A, Shackelford N, Sarkar S. Malaria in Africa: vector species' niche models and relative risk maps. PLoS One 2007; 2:e824. [PMID: 17786196 PMCID: PMC1950570 DOI: 10.1371/journal.pone.0000824] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2007] [Accepted: 08/06/2007] [Indexed: 11/19/2022] Open
Abstract
A central theoretical goal of epidemiology is the construction of spatial models of disease prevalence and risk, including maps for the potential spread of infectious disease. We provide three continent-wide maps representing the relative risk of malaria in Africa based on ecological niche models of vector species and risk analysis at a spatial resolution of 1 arc-minute (9 185 275 cells of approximately 4 sq km). Using a maximum entropy method we construct niche models for 10 malaria vector species based on species occurrence records since 1980, 19 climatic variables, altitude, and land cover data (in 14 classes). For seven vectors (Anopheles coustani, A. funestus, A. melas, A. merus, A. moucheti, A. nili, and A. paludis) these are the first published niche models. We predict that Central Africa has poor habitat for both A. arabiensis and A. gambiae, and that A. quadriannulatus and A. arabiensis have restricted habitats in Southern Africa as claimed by field experts in criticism of previous models. The results of the niche models are incorporated into three relative risk models which assume different ecological interactions between vector species. The “additive” model assumes no interaction; the “minimax” model assumes maximum relative risk due to any vector in a cell; and the “competitive exclusion” model assumes the relative risk that arises from the most suitable vector for a cell. All models include variable anthrophilicity of vectors and spatial variation in human population density. Relative risk maps are produced from these models. All models predict that human population density is the critical factor determining malaria risk. Our method of constructing relative risk maps is equally general. We discuss the limits of the relative risk maps reported here, and the additional data that are required for their improvement. The protocol developed here can be used for any other vector-borne disease.
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Affiliation(s)
- Alexander Moffett
- Section of Integrative Biology, University of Texas at Austin, Austin, Texas, United States of America
| | - Nancy Shackelford
- Section of Integrative Biology, University of Texas at Austin, Austin, Texas, United States of America
| | - Sahotra Sarkar
- Section of Integrative Biology, University of Texas at Austin, Austin, Texas, United States of America
- * To whom correspondence should be addressed. E-mail:
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Sogoba N, Doumbia S, Vounatsou P, Bagayoko MM, Dolo G, Traoré SF, Maïga HM, Touré YT, Smith T. Malaria transmission dynamics in Niono, Mali: the effect of the irrigation systems. Acta Trop 2007; 101:232-40. [PMID: 17362859 DOI: 10.1016/j.actatropica.2007.02.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2007] [Accepted: 02/12/2007] [Indexed: 11/22/2022]
Abstract
The type of water management and drainage system could be a potential reason for variation in malaria transmission in rice cultivation areas. To investigate this we have compared the population dynamics of Anopheles mosquitoes (Diptera, Culicidae) in rice plots with controlled and uncontrolled water depth, i.e. casiers and hors-casiers, respectively in the Office du Niger, Mali. We also compared malaria transmission in areas with mixed and casiers plots. Larval collection was performed fortnightly with the standard WHO dipping technique. Adult Anopheles were collected both by pyrethrum spray and landing catches. During the dry season rice cultivation cycle, the larval density in the hors-casier was significantly higher than in the casier plots. The larval peak in the casier plots was considerably smaller than the one in the hors-casier. During the rainy season, no significant difference was observed between the two plot types. However, larval densities begin to rise approximately one month earlier in the casier then in the hors-casier plots, and continued to increase trough the rice development phases until the grain filling/maturation phase, declining thereafter. In contrast, in the hors-casier rice plots larval density increased throughout the rice development. This difference was not significantly reflected in the adult vector density and man biting rate. However, high relative frequencies of Anopheles funestus, survival and entomological inoculation rates of An. gambiae s.l. were observed in the mixed plot sector.
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Affiliation(s)
- Nafomon Sogoba
- Malaria Research and Training Center, Faculty of Medicine, Pharmacy and Odonto-Stomatology, University of Bamako, Bamako, Mali.
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Walker K, Lynch M. Contributions of Anopheles larval control to malaria suppression in tropical Africa: review of achievements and potential. MEDICAL AND VETERINARY ENTOMOLOGY 2007; 21:2-21. [PMID: 17373942 DOI: 10.1111/j.1365-2915.2007.00674.x] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Malaria vector control targeting the larval stages of mosquitoes was applied successfully against many species of Anopheles (Diptera: Culicidae) in malarious countries until the mid-20th Century. Since the introduction of DDT in the 1940s and the associated development of indoor residual spraying (IRS), which usually has a more powerful impact than larval control on vectorial capacity, the focus of malaria prevention programmes has shifted to the control of adult vectors. In the Afrotropical Region, where malaria is transmitted mainly by Anopheles funestus Giles and members of the Anopheles gambiae Giles complex, gaps in information on larval ecology and the ability of An. gambiae sensu lato to exploit a wide variety of larval habitats have discouraged efforts to develop and implement larval control strategies. Opportunities to complement adulticiding with other components of integrated vector management, along with concerns about insecticide resistance, environmental impacts, rising costs of IRS and logistical constraints, have stimulated renewed interest in larval control of malaria vectors. Techniques include environmental management, involving the temporary or permanent removal of anopheline larval habitats, as well as larviciding with chemical or biological agents. This present review covers large-scale trials of anopheline larval control methods, focusing on field studies in Africa conducted within the past 15 years. Although such studies are limited in number and scope, their results suggest that targeting larvae, particularly in human-made habitats, can significantly reduce malaria transmission in appropriate settings. These approaches are especially suitable for urban areas, where larval habitats are limited, particularly when applied in conjunction with IRS and other adulticidal measures, such as the use of insecticide treated bednets.
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Affiliation(s)
- K Walker
- Department of Entomology, College of Agriculture and Life Sciences, University of Arizona, Tucson, Arizona 85721, USA.
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Abstract
Despite its key role in determining the stability and intensity of malaria transmission, the infectiousness of human populations to mosquitoes has rarely been estimated. Field-based analyses of malaria transmission have frequently relied on the prevalence of asexual parasites or gametocytes as proxies for infectiousness. We now summarize empirical data on human infectiousness from Africa and Papua New Guinea. Over a wide range of transmission intensities there is little relationship between the infectiousness of human populations to vector mosquitoes and mosquito-to-human transmission intensity. We compare these data with the predictions of a stochastic simulation model of Plasmodium falciparum epidemiology. This model predicted little variation in the infectiousness of the human population for entomologic inoculation rates (EIRs) greater than approximately 10 infectious bites per year, demonstrating that the lack of relationship between the EIR and the infectious reservoir can be explained without invoking any effects of acquired transmission-blocking immunity. The near absence of field data from areas with an EIR < 10 per year precluded validation of the model predictions for low EIR values. These results suggest that interventions reducing mosquito-to-human transmission will have little or no effect on human infectiousness at the levels of transmission found in most rural areas of sub-Saharan Africa. Unless very large reductions in transmission can be achieved, measures to prevent mosquito-to-human transmission need to be complemented with interventions that reduce the density or infectiousness of blood stage parasites.
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Affiliation(s)
- Gerry F Killeen
- Ifakara Health Research and Development Center, Ifakara, Tanzania.
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Diuk-Wasser MA, Dolo G, Bagayoko M, Sogoba N, Toure MB, Moghaddam M, Manoukis N, Rian S, Traore SF, Taylor CE. Patterns of irrigated rice growth and malaria vector breeding in Mali using multi-temporal ERS-2 synthetic aperture radar. INTERNATIONAL JOURNAL OF REMOTE SENSING 2006; 27:535-548. [PMID: 17710188 PMCID: PMC1948877 DOI: 10.1080/01431160500104350] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
We explored the use of the European Remote Sensing Satellite 2 Synthetic Aperture Radar (ERS-2 SAR) to trace the development of rice plants in an irrigated area near Niono, Mali and relate that to the density of anopheline mosquitoes, especially An. gambiae. This is important because such mosquitoes are the major vectors of malaria in sub-Saharan Africa, and their development is often coupled to the cycle of rice development. We collected larval samples, mapped rice fields using GPS and recorded rice growth stages simultaneously with eight ERS-2 SAR acquisitions. We were able to discriminate among rice growth stages using ERS-2 SAR backscatter data, especially among the early stages of rice growth, which produce the largest numbers of larvae. We could also distinguish between basins that produced high and low numbers of anophelines within the stage of peak production. After the peak, larval numbers dropped as rice plants grew taller and thicker, reducing the amount of light reaching the water surface. ERS-2 SAR backscatter increased concomitantly. Our data support the belief that ERS-2 SAR data may be helpful for mapping the spatial patterns of rice growth, distinguishing different agricultural practices, and monitoring the abundance of vectors in nearby villages.
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Affiliation(s)
- M A Diuk-Wasser
- Department of Epidemiology and Public Health, Yale School of Medicine, New Haven, Connecticut
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26
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van den Berg H, Knols BGJ. The Farmer Field School: a method for enhancing the role of rural communities in malaria control ? Malar J 2006; 5:3. [PMID: 16423295 PMCID: PMC1382236 DOI: 10.1186/1475-2875-5-3] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2005] [Accepted: 01/19/2006] [Indexed: 11/10/2022] Open
Abstract
Malaria has strong linkages with agriculture, and farmers in malarious regions have a central position in creating or controlling the conditions that favour disease transmission. An interdisciplinary and integrated approach is needed to involve farmers and more than one sector in control efforts. It is suggested that malaria control can benefit from a complementary intervention in rural development, the Farmer Field School (FFS) on Integrated Pest Management (IPM). This is a form of education that uses experiential learning methods to build farmers' expertise, and has proven farm-level and empowerment effects. The benefits of incorporating malaria control into the IPM curriculum are discussed. An example of a combined health-agriculture curriculum, labeled Integrated Pest and Vector Management (IPVM), developed in Sri Lanka is presented. Institutional ownership and support for IPVM could potentially be spread over several public sectors requiring a process for institutional learning and reform.
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Affiliation(s)
- Henk van den Berg
- Laboratory of Entomology, Wageningen University and Research Centre, P.O. Box 8031, 6700 EH, Wageningen, The Netherlands
| | - Bart GJ Knols
- Laboratory of Entomology, Wageningen University and Research Centre, P.O. Box 8031, 6700 EH, Wageningen, The Netherlands
- International Atomic Energy Agency (IAEA), Agency's Laboratories Seibersdorf, Seibersdorf A-2444, Austria
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Fillinger U, Sonye G, Killeen GF, Knols BGJ, Becker N. The practical importance of permanent and semipermanent habitats for controlling aquatic stages of Anopheles gambiae sensu lato mosquitoes: operational observations from a rural town in western Kenya. Trop Med Int Health 2005; 9:1274-89. [PMID: 15598259 DOI: 10.1111/j.1365-3156.2004.01335.x] [Citation(s) in RCA: 149] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Control of aquatic-stage Anopheles is one of the oldest and most historically successful interventions to prevent malaria, but it has seen little application in Africa. Consequently, the ecology of immature afrotropical Anopheles has received insufficient attention. We therefore examined the population dynamics of African anopheline and culicine mosquitoes using operationally practicable techniques to examine the relative importance and availability of different larval habitats in an area of perennial malaria transmission in preparation for a pilot-scale larval control programme. The study was conducted in Mbita, a rural town on the shores of Lake Victoria in Western Kenya, over 20 months. Weekly larval surveys were conducted to identify the availability of stagnant water, habitat characteristics and larval densities. Adult mosquitoes were collected indoors at fortnightly intervals. Availability of aquatic habitats and abundance of mosquito larvae were directly correlated with rainfall. Adult mosquito densities followed similar patterns but with a time-lag of approximately 1 month. About 70% of all available habitats were man-made, half of them representing cement-lined pits. On average, 67% of all aquatic habitats on a given sampling date were colonized by Anopheles larvae, of which all identified morphologically were A. gambiae sensu lato. Natural and artificial habitats were equally productive over the study period and larval densities were positively correlated with presence of tufts of low vegetation and negatively with non-matted algal content. The permanence of a habitat had no significant influence on larval productivity. We conclude that A. gambiae is broadly distributed across a variety of habitat types, regardless of permanence. All potential breeding sites need to be considered as sources of malaria risk at any time of the year and exhaustively targeted in any larval control intervention.
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Affiliation(s)
- Ulrike Fillinger
- School of Biological and Biomedical Sciences, University of Durham, Durham, UK.
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Pålsson K, Jaenson TGT, Dias F, Laugen AT, Björkman A. Endophilic Anopheles mosquitoes in Guinea Bissau, west Africa, in relation to human housing conditions. JOURNAL OF MEDICAL ENTOMOLOGY 2004; 41:746-752. [PMID: 15311470 DOI: 10.1603/0022-2585-41.4.746] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Environmental risk factors associated with increased malaria mosquito (Anopheles) abundance indoors were studied in a suburban area, Antula, of Guinea Bissau, during the rainy seasons of 1993-1995. All bedrooms in 30 houses were searched for resting mosquitoes three times each year. The most abundant mosquito was An. gambiae s.s. Significantly greater numbers of resting mosquitoes were present in rooms with open eaves and in houses with a well on the compound. Pigs were the most common domestic animals in Antula. Presence of pigs in a house was associated with increased mosquito abundance in the bedrooms of the same house. The abundance of female mosquitoes also increased with increasing human biomass per square meter of bedroom area.
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Affiliation(s)
- Katinka Pålsson
- Department of Systematic Zoology, Evolutionary Biology Centre, Uppsala University, Norbyvägen, Uppsala, Sweden
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Dolo G, Briët OJT, Dao A, Traoré SF, Bouaré M, Sogoba N, Niaré O, Bagayogo M, Sangaré D, Teuscher T, Touré YT. Malaria transmission in relation to rice cultivation in the irrigated Sahel of Mali. Acta Trop 2004; 89:147-59. [PMID: 14732237 DOI: 10.1016/j.actatropica.2003.10.014] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Seven cross-sectional entomological surveys were carried out from September 1995 to February 1998 in three irrigated rice growing villages and three villages without irrigated agriculture in the area surrounding Niono, located 350km north-east of Bamako, Mali. The transmission pattern differed markedly between the two zones. In the irrigated zone, the transmission of malaria was fairly constant over the seasons at a low level. In the non-irrigated zone, transmission was mostly below detection level during the dry season, whereas it was high toward the end of the rainy season. In the irrigated zone, high densities of mosquitoes were correlated with low anthropophily, low sporozoite indices and probably low survival rates. In the non-irrigated zone, mosquito densities were lower and these relationships were less pronounced. Differential use of mosquito nets in the two zones may have been an important factor in the observed differences in transmission. The presence of cattle may also have played an important role. Two mosquito-catching methods (human landing catch and spray catch) were compared.
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Affiliation(s)
- Guimogo Dolo
- Département d'Epidémiologie des Affections Parasitaires, Faculté de Médecine, de Pharmacie et d'Odonto-Stomatologie, BP 1805, Bamako, Mali
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Diuk-Wasser MA, Bagayoko M, Sogoba N, Dolo G, Touré MB, Traoré SF, Taylor CE. Mapping rice field anopheline breeding habitats in Mali, West Africa, using Landsat ETM+ sensor data. INTERNATIONAL JOURNAL OF REMOTE SENSING 2004; 25:359-376. [PMID: 18084628 PMCID: PMC2140004 DOI: 10.1080/01431160310001598944] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
The aim of this study was to determine whether remotely sensed data could be used to identify rice-related malaria vector breeding habitats in an irrigated rice growing area near Niono, Mali. Early stages of rice growth show peak larval production, but Landsat sensor data are often obstructed by clouds during the early part of the cropping cycle (rainy season). In this study, we examined whether a classification based on two Landsat Enhanced Thematic Mapper (ETM)+ scenes acquired in the middle of the season and at harvesting times could be used to map different land uses and rice planted at different times (cohorts), and to infer which rice growth stages were present earlier in the season. We performed a maximum likelihood supervised classification and evaluated the robustness of the classifications with the transformed divergence separability index, the kappa coefficient and confusion matrices. Rice was distinguished from other land uses with 98% accuracy and rice cohorts were discriminated with 84% accuracy (three classes) or 94% (two classes). Our study showed that optical remote sensing can reliably identify potential malaria mosquito breeding habitats from space. In the future, these 'crop landscape maps' could be used to investigate the relationship between cultivation practices and malaria transmission.
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Affiliation(s)
- M. A. Diuk-Wasser
- Department of Organismic Biology, Ecology and Evolution, University of California, Los Angeles, 621 Charles Young Drive, Los Angeles, CA 90095-1606, USA
- *Corresponding author; e-mail:
| | - M. Bagayoko
- Malaria Research and Training Center, Faculté de Médecine, de Pharmacie and d'Odonto-Stomatologie, Université du Mali, Bamako, B.P. 1805, Mali
| | - N. Sogoba
- Malaria Research and Training Center, Faculté de Médecine, de Pharmacie and d'Odonto-Stomatologie, Université du Mali, Bamako, B.P. 1805, Mali
| | - G. Dolo
- Malaria Research and Training Center, Faculté de Médecine, de Pharmacie and d'Odonto-Stomatologie, Université du Mali, Bamako, B.P. 1805, Mali
| | - M. B. Touré
- Malaria Research and Training Center, Faculté de Médecine, de Pharmacie and d'Odonto-Stomatologie, Université du Mali, Bamako, B.P. 1805, Mali
| | - S. F. Traoré
- Malaria Research and Training Center, Faculté de Médecine, de Pharmacie and d'Odonto-Stomatologie, Université du Mali, Bamako, B.P. 1805, Mali
| | - C. E. Taylor
- Department of Organismic Biology, Ecology and Evolution, University of California, Los Angeles, 621 Charles Young Drive, Los Angeles, CA 90095-1606, USA
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Koenraadt CJM, Paaijmans KP, Githeko AK, Knols BGJ, Takken W. Egg hatching, larval movement and larval survival of the malaria vector Anopheles gambiae in desiccating habitats. Malar J 2003; 2:20. [PMID: 12919636 PMCID: PMC183857 DOI: 10.1186/1475-2875-2-20] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2003] [Accepted: 07/01/2003] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Although the effects of rainfall on the population dynamics of the malaria vector Anopheles gambiae have been studied in great detail, the effects of dry periods on its survival remain less clear. METHODS The effects of drying conditions were simulated by creating desiccated habitats, which consisted of trays filled with damp soil. Experiments were performed in these trays to (i) test the ability of An. gambiae sensu stricto eggs to hatch on damp soil and for larvae to reach an artificial breeding site at different distances of the site of hatching and (ii) to record survival of the four larval stages of An. gambiae s.s. when placed on damp soil. RESULTS Eggs of An. gambiae s.s. hatched on damp soil and emerging larvae were capable of covering a distance of up to 10 cm to reach surface water enabling further development. However, proportions of larvae reaching the site decreased rapidly with increasing distance. First, second and third-instar larvae survived on damp soil for an estimated period of 64, 65 and 69 hrs, respectively. Fourth-instar larvae survived significantly longer and we estimated that the maximum survival time was 113 hrs. CONCLUSION Short-term survival of aquatic stages of An. gambiae on wet soil may be important and adaptive when considering the transient nature of breeding sites of this species in sub-Saharan Africa. In addition, the results suggest that, for larval vector control methods to be effective, habitats should remain drained for at least 5 days to kill all larvae (e.g. in rice fields) and habitats that recently dried up should be treated as well, if larvicidal agents are applied.
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Affiliation(s)
- Constantianus JM Koenraadt
- Laboratory of Entomology, Department of Plant Sciences, Wageningen University, P.O. Box 8031, 6700 EH Wageningen, The Netherlands
| | - Krijn P Paaijmans
- Laboratory of Entomology, Department of Plant Sciences, Wageningen University, P.O. Box 8031, 6700 EH Wageningen, The Netherlands
| | - Andrew K Githeko
- Kenya Medical Research Institute, Climate and Human Health Research Unit, P.O. Box 1578, Kisumu, Kenya
| | - Bart GJ Knols
- Laboratory of Entomology, Department of Plant Sciences, Wageningen University, P.O. Box 8031, 6700 EH Wageningen, The Netherlands
- New address: Entomology Unit, FAO/IAEA, Agency's Laboratories Seibersdorf, A-1400 Vienna, Austria
| | - Willem Takken
- Laboratory of Entomology, Department of Plant Sciences, Wageningen University, P.O. Box 8031, 6700 EH Wageningen, The Netherlands
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