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Spatial and temporal distribution of the malaria mosquito Anopheles arabiensis in northern Sudan: influence of environmental factors and implications for vector control
Tellal B Ageep, Jonathan Cox, M'oawia M Hassan, Bart GJ Knols, Mark Q Benedict, Colin A Malcolm, Ahmed Babiker, Badria B El Sayed
Malaria Journal , 2009, DOI: 10.1186/1475-2875-8-123
Abstract: Monthly cross-sectional larval surveys were carried out between March 2005 and May 2007 in two localities (Dongola and Merowe) adjacent to the river Nile. A stratified random sampling strategy based on the use of Remote Sensing (RS), Geographical Information Systems (GIS) and the Global Positioning System (GPS) was used to select survey locations. Breeding sites were mapped using GPS and data on larval density and breeding site characteristics were recorded using handheld computers. Bivariate and multivariate logistic regression models were used to identify breeding site characteristics associated with increased risk of presence of larvae. Seasonal patterns in the proportion of breeding sites positive for larvae were compared visually to contemporaneous data on climate and river height.Of a total of 3,349 aquatic habitats sampled, 321 (9.6%) contained An. arabiensis larvae. The frequency with which larvae were found varied markedly by habitat type. Although most positive sites were associated with temporary standing water around the margins of the main Nile channel, larvae were also found at brickworks and in areas of leaking pipes and canals – often far from the river. Close to the Nile channel, a distinct seasonal pattern in larval populations was evident and appeared to be linked to the rise and fall of the river level. These patterns were not evident in vector populations breeding in artificial water sources away from the river.The GIS-based survey strategy developed in this study provides key data on the population dynamics of An. arabiensis in Northern State. Quantitative estimates of the contributions of various habitat types and their proximity to settlements provide a basis for planning a strategy for reducing malaria risk by elimination of the vector population.Malaria is a significant health problem in Sudan, affecting 52% of outpatients and accounting for 9% of all hospitals deaths [1]. Given its diversity and the size of the country, the largest in Afri
A malaria transmission-directed model of mosquito life cycle and ecology
Philip A Eckhoff
Malaria Journal , 2011, DOI: 10.1186/1475-2875-10-303
Abstract: A new model is presented for mosquito population dynamics, effects of weather, and impacts of multiple simultaneous interventions. This model is then embedded in a large-scale individual-based simulation and results for local elimination of malaria are discussed. Mosquito population behaviours, such as anthropophily and indoor feeding, are included to study their effect upon the efficacy of vector control-based elimination campaigns.Results for vector control tools, such as bed nets, indoor spraying, larval control and space spraying, both alone and in combination, are displayed for a single-location simulation with vector species and seasonality characteristic of central Tanzania, varying baseline transmission intensity and vector bionomics. The sensitivities to habitat type, anthropophily, indoor feeding, and baseline transmission intensity are explored.The ability to model a spectrum of local vector species with different ecologies and behaviours allows local customization of packages of interventions and exploration of the effect of proposed new tools.Malaria is transmitted by the blood feeding of infectious female Anopheles mosquitoes, and understanding mosquito ecology and population dynamics can inform how best to defeat malaria. Malaria is an important global health issue, causing over half a billion cases and on the order of one million deaths a year [1], and is the focus of a global eradication campaign announced in 2007. Basic vector ecology is a fundamental driver of transmission patterns, and changes in land usage [2] or land modification can dramatically change transmission for better or worse. The growing urbanization in Africa is a powerful current example of such phenomena [3]. Climate and weather affect larval development and parasite maturation within the infected mosquito, and spatial models are able to predict malaria prevalence based primarily on climate details in the absence of interventions [4]. This climate-driven predictability has broken
Bio-efficacy and operational feasibility of alphacypermethrin (Fendona) impregnated mosquito nets to control rural malaria in northern India
M.A. Ansari & R.K. Razdan
Journal of Vector Borne Diseases , 2003,
Abstract: Bio-efficacy and operational feasibility of alphacypermethrin treated nets was evaluated in certainvillages of District Ghaziabad (U.P.). Results revealed that poly-filament nylon nets treated with alphacypermethrinsuspension concentrate (g/l) formulation @ 25 mg/m2 has shown repellent action(26.5 ± 8.1), excito repellent action (93.7 ± 8.1) and killing action (100%) against An. culicifacieslanded on treated nets. Significant reduction in indoor resting density of An. culicifacies in humandwellings was also observed in treated nets village (p < 0.05). Instant killing action of treated netsdid provide complete protection to inhabitants sleeping inside the net from An. culicifacies bites.The persistent use of nets by the inhabitants has also resulted significant reduction in malaria cases(p < 0.05). It was interesting to note that not even a single case of falciparum malaria was observedafter distribution of treated nets in spite of the fact that at no point of time cent per centcompliance of net usage was observed during the study period. Bio-assay tests revealed that treatednets can produce up to 70% mortality in An. culicifacies for about 22 weeks and as such onlyone treatment with insecticide is required in a year in seasonal transmission area to protect frommalaria. The study also revealed that treated nets can be stored at room temperature for about 10months without loosing their efficacy suggesting thereby that malaria outbreaks can be tackled bythe nets if adequate treated nets are stored in core problem districts. It was also revealed that An.culicifacies is a late night biter and as such treated nets can be used successfully against this species.
Mosquito Longevity, Vector Capacity, and Malaria Incidence in West Timor and Central Java, Indonesia  [PDF]
Ermi Ndoen,Clyde Wild,Pat Dale,Neil Sipe,Mike Dale
ISRN Public Health , 2012, DOI: 10.5402/2012/143863
Abstract: The aim of this paper was to relate anopheline mosquito longevity to malaria incidence in two areas in Indonesia: West Timor and Central Java. We estimated the physiological age of females captured landing on humans or resting inside and outside buildings. The estimate was based on the state of the ovaries and was used to estimate longevity. The results showed that there were large differences between the two areas surveyed. In West Timor the longevity of the anophelines ranged from 13 to 23 days, sufficient for completing the intrinsic incubation cycle and for malaria transmission, whereas in Central Java the longevity was only 3 days, insufficient both for incubation and for transmission. We concluded that the West Timor study area had a greater risk of malaria transmission than that of Central Java and this was supported by village survey data that showed greater malaria incidence in West Timor than in Central Java. 1. Introduction Malaria is a life-threatening disease in Indonesia with an estimated 15 million cases and 42,000 deaths every year [1–3]. It is transmitted by infected Anopheles mosquitoes. Although there are 24 Anopheles species recorded throughout Indonesia [4–6], not all are important in malaria transmission. The most extensively occurring species of anopheline mosquitoes in Indonesia are An. sundaicus, An. subpictus, An. barbirostris, An. maculatus, An. aconitus, and An. bablabacensis, [5, 7] and all are implicated in malaria transmission. Malaria transmission has a complex parasite life cycle which depends on both humans and mosquitoes [8]. In the mosquito, the malarial parasite (Plasmodium spp.) develops an exogenous sexual phase (sporogony cycle). When the sporozoites have developed, they make their way to the mosquito saliva glands, from which they are transmitted to humans via the mosquito bite. Malaria develops in a new cycle within the human host. An infective mosquito is a prerequisite for malaria transmission. It takes between 8 and 35 days to complete the parasite’s life cycle in the mosquito host, depending on the condition of the environment and the species of malaria parasites [9–11]. Takken et al. [5] highlighted important factors for mosquitoes to become malaria vectors. These include mosquito density, behavioural factors, and vectorial capacity. Behavioural characteristics include feeding habits, anthropophily or zoophily [12]; house-frequenting resting habits, exophily or endophily [13]; and site of feeding, endophagy or exophagy [12]. Vectorial capacity and the ability to transmit malaria is related to mosquito
Anthropophily of Malaria Vectors in Kahnouj District, South of Kerman, Iran
HR Basseri,SH Moosakazemi,S Yosafi,M Mohebali
Iranian Journal of Public Health , 2005,
Abstract: This study was conducted to investigate hematophagic tendencies of the malaria vector based on a seasonal basis as well as by geographical region in a malaria endemic area in Kahnouj, southern Iran. This study was carried out for 14 months from Apr/ 2002 up to the end of May 2003. Female anophelines were collected from different shelters in hilly and plain regions of Kahnouj district and their blood meal was tested using ELISA test methods. The five vectors that were active in the study area consisted of An. fluviatilis, An. stephensi, An. dthali, An. culicifacies, and An. superpictus. The dominant Anopheline in hilly areas was An. fluviatilis sibling species T. This species was active during whole year and reached a peak in December. In contrast the dominant species in flat regions was An. stephensi which showed strongly endophilic behavior with two seasonal activity peaks. The anthropophilic index for An. fluviatilis and An. stephensi was estimated at 2.68% and 0.5%, respectively. The population of other species was too low and they did not show a propensity for human blood. The most malaria cases occurred in the hilly area where An. fluviatilis is the active dominant species. It seems that An. fluviatilis is responsible for transmission of malaria in hilly districts of Kahnouj. Thus malaria transmission in this study area is much influenced by resident’s rest habits while a wild vector, An. fluviatilis shows exophilic behavior and uses microclimate shelters with high incidence of human blood feeding. Thus, adapting people to use personal protection such as a bed net instead of residual spraying may be considered as an effective measure in malaria control in hilly regions.
A quantitative risk assessment approach for mosquito-borne diseases: malaria re-emergence in southern France
Nicolas Pon?on, Annelise Tran, Céline Toty, Adrian JF Luty, Didier Fontenille
Malaria Journal , 2008, DOI: 10.1186/1475-2875-7-147
Abstract: Receptivity (vectorial capacity) and infectivity (vector susceptibility) were inferred using an innovative probabilistic approach and considering both Plasmodium falciparum and Plasmodium vivax. Each parameter of receptivity (human biting rate, anthropophily, length of trophogonic cycle, survival rate, length of sporogonic cycle) and infectivity were estimated based on field survey, bibliographic data and expert knowledge and fitted with probability distributions taking into account the variability and the uncertainty of the estimation. Spatial and temporal variations of the parameters were determined using environmental factors derived from satellite imagery, meteorological data and entomological field data. The entomological risk (receptivity/infectivity) was calculated using 10,000 different randomly selected sets of values extracted from the probability distributions. The result was mapped in the Camargue area. Finally, vulnerability (number of malaria imported cases) was inferred using data collected in regional hospitals.The entomological risk presented large spatial, temporal and Plasmodium species-dependent variations. The sensitivity analysis showed that susceptibility, survival rate and human biting rate were the three most influential parameters for entomological risk. Assessment of vulnerability showed that among the imported cases in the region, only very few were imported in at-risk areas.The current risk of malaria re-emergence seems negligible due to the very low number of imported Plasmodium. This model demonstrated its efficiency for mosquito-borne diseases risk assessment.In the past, malaria was endemic and constituted a major health issue in France in marshy areas, particularly the Camargue, which was an active focus until the beginning of the 20th century. Malaria decreased drastically due to the draining of marshes, rearing of livestock, improvement of housing and living conditions and the use of quinine [1]. Malaria disappeared from the Camar
Survivorship of Anopheles darlingi (Diptera: Culicidae) in Relation with Malaria Incidence in the Brazilian Amazon  [PDF]
Fábio Saito Monteiro de Barros,Nildimar Alves Honório,Mércia Eliane Arruda
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0022388
Abstract: We performed a longitudinal study of adult survival of Anopheles darlingi, the most important vector in the Amazon, in a malarigenous frontier zone of Brazil. Survival rates were determined from both parous rates and multiparous dissections. Anopheles darlingi human biting rates, daily survival rates and expectation of life where higher in the dry season, as compared to the rainy season, and were correlated with malaria incidence. The biting density of mosquitoes that had survived long enough for completing at least one sporogonic cycle was related with the number of malaria cases by linear regression. Survival rates were the limiting factor explaining longitudinal variations in Plasmodium vivax malaria incidence and the association between adult mosquito survival and malaria was statistically significant by logistic regression (P<0.05). Survival rates were better correlated with malaria incidence than adult mosquito biting density. Mathematical modeling showed that P. falciparum and P. malariae were more vulnerable to changes in mosquito survival rates because of longer sporogonic cycle duration, as compared to P. vivax, which could account for the low prevalence of the former parasites observed in the study area. Population modeling also showed that the observed decreases in human biting rates in the wet season could be entirely explained by decreases in survival rates, suggesting that decreased breeding did not occur in the wet season, at the sites where adult mosquitoes were collected. For the first time in the literature, multivariate methods detected a statistically significant inverse relation (P<0.05) between the number of rainy days per month and daily survival rates, suggesting that rainfall may cause adult mortality.
Malaria mosquito resistance revealed
Cathy Holding
Genome Biology , 2003, DOI: 10.1186/gb-spotlight-20030508-01
Abstract: Weill et al. compared the sequence of an organophosphate target (the acetylcholinesterase gene ace-1) in a resistant and susceptible strain of the mosquito Culex pipiens - vector of the West Nile virus. Analysis revealed one of 27 nucleotide differences resulting in a G119S substitution that they localized to a position near the active site of the enzyme. Further analysis confirmed the coincidence of this amino acid substitution with insecticide resistance in several other strains of the same species, and it was also identified in the ace-1 of a resistant strain of A. gambiae. In addition, they showed that this amino acid substitution has arisen independently at least three times in mosquito species."The development of new insecticides that can specifically inhibit the G119S mutant form of acetylcholinestease-1 will be crucial in overcoming the spread of resistance," conclude the authors.
Heterogeneity of malaria prevalence in alluvial gold mining areas in Northern Mato Grosso State, Brazil
Barbieri, Alisson Flávio;Sawyer, Diana Oya;
Cadernos de Saúde Pública , 2007, DOI: 10.1590/S0102-311X2007001200009
Abstract: this paper analyzes factors affecting the risk of malaria among individuals working in wildcat gold mining camps (garimpos) in northern mato grosso state in the brazilian amazon. historically, such mining camps have the locations with the highest malaria prevalence in the brazilian amazon. however, little attention has focused on understanding the disease from the internal perspective of the mining camps themselves, such as the mining population's characteristics and its spatial organization. this paper adopts a stepwise logistic model to identify spatial, occupational-exposure, and cultural factors that affect malaria prevalence. according to the results, differences among individuals working and/or living in the gold mining areas could produce different exposure to the disease and thus to different risk of malaria prevalence. understanding these differences may provide an important tool for identifying risk profiles in the gold mining and related population and for informing programs for prevention and treatment of malaria in the amazon.
Mosquito transmission of the rodent malaria parasite Plasmodium chabaudi
Spence Philip J,Jarra William,Lévy Prisca,Nahrendorf Wiebke
Malaria Journal , 2012, DOI: 10.1186/1475-2875-11-407
Abstract: Background Serial blood passage of Plasmodium increases virulence, whilst mosquito transmission inherently regulates parasite virulence within the mammalian host. It is, therefore, imperative that all aspects of experimental malaria research are studied in the context of the complete Plasmodium life cycle. Methods Plasmodium chabaudi chabaudi displays many characteristics associated with human Plasmodium infection of natural mosquito vectors and the mammalian host, and thus provides a unique opportunity to study the pathogenesis of malaria in a single infection setting. An optimized protocol that permits efficient and reproducible vector transmission of P. c. chabaudi via Anopheles stephensi was developed. Results and conclusions This protocol was utilized for mosquito transmission of genetically distinct P. c. chabaudi isolates, highlighting differential parasite virulence within the mosquito vector and the spectrum of host susceptibility to infection initiated via the natural route, mosquito bite. An apposite experimental system in which to delineate the pathogenesis of malaria is described in detail.
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