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Search Results: 1 - 10 of 410027 matches for " Joseph M. Mwangangi "
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Seasonal mosquito larval abundance and composition in Kibwezi, lower eastern Kenya
Joseph M. Mwangangi,Ephantus J. Muturi,Charles M. Mbogo
Journal of Vector Borne Diseases , 2009,
Abstract: Background & objectives: Changes in weather patterns especially rainfall affects the distribution and densities of mosquitoes. The objective of this study was to describe mosquito aquatic habitats, to determine larval abundance, species composition, and habitat types found in Kasayani village of Kibwezi division.Methods: A cross-sectional survey of mosquito larval habitats was conducted in Kasayani village in Kibwezi division to determine species composition, larval abundance, and habitat types found in this village. This survey was conducted during the rainy season in November and December 2006 and during the dry season in February and March 2007. Larvae were collected using the standard dipping technique and a total of 24 habitats were sampled. The primary habitats identified were water reservoir tanks, puddles, temporary pools, and tyre tracks. Results: A total of 2660 mosquito larvae were collected of which 2140 (80.45%) were culicines, 503 (18.91%) were Anopheles and 17 (0.64%) were pupae. For culicines, 1787 (83.5%) were categorized as early instars and 353 (16.5%) were as late instars while in the Anopheles, 425 (84.49%) were classified as early instars and 78 (15.51%) were late instars. Morphological identification of the III and IV instar larvae by use of microscopy yielded 16.24% (n = 70) Anopheles gambiae complex, 1.16% (n = 5) An. funestus, 0.70% (n = 3) An. coustani, 42.46% (n = 183) Culex quinquefasciatus, 6.26% (n = 27) Cx. duttoni, and 33.18% (n = 143) Ae. aegypti. Puddles, tyre tracks and pools had highly turbid water while water reservoir tanks had clear water. Anopheles gambiae and Cx. quinquefasciatus were found in all habitat categories while Ae. aegypti were found only in water storage tanks. Interpretation & conclusion: The mosquito larval densities indicate that the inhabitants of this village are at risk of mosquito-borne diseases including malaria, which is one of the greatest causes of morbidity and mortality in this area. Furthermore, mosquito control measures targeting both the mosquito immatures and adults should be enhanced especially during the rainy season to ensure maximum protection of the inhabitants.
Spatial distribution and habitat characterisation of Anopheles larvae along the Kenyan coast
Joseph M. Mwangangi,Charles M. Mbogo,Ephantus J. Muturi,Joseph G. Nzovu
Journal of Vector Borne Diseases , 2007,
Abstract: Background & objectives: A study was conducted to characterise larval habitats and to determine spatialheterogeneity of the Anopheles mosquito larvae. The study was conducted from May to June 1999 innine villages along the Kenyan coast.Methods: Aquatic habitats were sampled by use of standard dipping technique. The habitats werecharacterised based on size, pH, distance to the nearest house, coverage of canopy, surface debris, algaeand emergent plants, turbidity, substrate, and habitat type.Results: A total of 110 aquatic habitats like stream pools (n = 10); puddles (n = 65); tire tracks (n =5); ponds (n = 5) and swamps (n = 25) were sampled in nine villages located in three districts of theKenyan coast. A total of 7,263 Anopheles mosquito larvae were collected, 63.9% were early instarsand 36.1% were late instars. Morphological identification of the III and IV instar larvae by use ofmicroscopy yielded 90.66% (n = 2,377) Anopheles gambiae Complex, 0.88% (n = 23) An. funestus,An. coustani 7.63% (n = 200), An. rivulorum 0.42% (n = 11), An. pharoensis 0.19% (n = 5), An.swahilicus 0.08% (n = 2), An. wilsoni 0.04% (n = 1) and 0.11% (n = 3) were unidentified. A subset ofthe An. gambiae Complex larvae identified morphologically, was further analysed using rDNA-PCRtechnique resulting in 68.22% (n = 1,290) An. gambiae s.s., 7.93% (n = 150) An. arabiensis and 23.85%(n = 451) An. merus. Multiple logistic regression model showed that emergent plants (p = 0.019), andfloating debris (p = 0.038) were the best predictors of An. gambiae larval abundance in these habitats.Interpretation & conclusion: Habitat type, floating debris and emergent plants were found to be thekey factors determining the presence of Anopheles larvae in the habitats. For effective larval control,the type of habitat should be considered and most productive habitat type be given a priority in themosquito abatement programme
The bionomics of Anopheles merus (Diptera: Culicidae) along the Kenyan coast
Kipyab Pamela C,Khaemba Battan M,Mwangangi Joseph M,Mbogo Charles M
Parasites & Vectors , 2013, DOI: 10.1186/1756-3305-6-37
Abstract: Background Anopheles merus, a sibling species of the Anopheles gambiae complex occurs along the East African coast but its biology and role in malaria transmission in this region is poorly understood. We evaluated the blood feeding pattern and the role of this species in malaria transmission in Malindi district, Coastal Kenya. Methods Adult mosquitoes were collected indoors by CDC light traps and Pyrethrum Spray Catch and outdoors by CDC light traps. Anopheles females were identified to species by morphological characteristics and sibling species of An. gambiae complex distinguished by rDNA polymerase chain reaction (PCR). Screening for host blood meal sources and presence or absence of Plasmodium falciparum circumsporozoite proteins was achieved by Enzyme Linked Immunosorbent Assays (ELISA). Results Anopheles merus comprised 77.8% of the 387 Anopheles gambiae s.l adults that were collected. Other sibling species of Anopheles gambiae s.l identified in the study site included An. arabiensis(3.6%), and An. gambiae s.s. (8%). The human blood index for An. merus was 0.12, while the sporozoite rate was 0.3%. Conclusion These findings suggest that An. merus can play a minor role in malaria transmission along the Kenyan Coast and should be a target for vector control which in turn could be applied in designing and implementing mosquito control programmes targeting marsh-breeding mosquitoes; with the ultimate goal being to reduce the transmission of malaria associated with these vectors.
Shifts in malaria vector species composition and transmission dynamics along the Kenyan coast over the past 20 years
Mwangangi Joseph M,Mbogo Charles M,Orindi Benedict O,Muturi Ephantus J
Malaria Journal , 2013, DOI: 10.1186/1475-2875-12-13
Abstract: Background Over the past 20 years, numerous studies have investigated the ecology and behaviour of malaria vectors and Plasmodium falciparum malaria transmission on the coast of Kenya. Substantial progress has been made to control vector populations and reduce high malaria prevalence and severe disease. The goal of this paper was to examine trends over the past 20 years in Anopheles species composition, density, blood-feeding behaviour, and P. falciparum sporozoite transmission along the coast of Kenya. Methods Using data collected from 1990 to 2010, vector density, species composition, blood-feeding patterns, and malaria transmission intensity was examined along the Kenyan coast. Mosquitoes were identified to species, based on morphological characteristics and DNA extracted from Anopheles gambiae for amplification. Using negative binomial generalized estimating equations, mosquito abundance over the period were modelled while adjusting for season. A multiple logistic regression model was used to analyse the sporozoite rates. Results Results show that in some areas along the Kenyan coast, Anopheles arabiensis and Anopheles merus have replaced An. gambiae sensu stricto (s.s.) and Anopheles funestus as the major mosquito species. Further, there has been a shift from human to animal feeding for both An. gambiae sensu lato (s.l.) (99% to 16%) and An. funestus (100% to 3%), and P. falciparum sporozoite rates have significantly declined over the last 20 years, with the lowest sporozoite rates being observed in 2007 (0.19%) and 2008 (0.34%). There has been, on average, a significant reduction in the abundance of An. gambiae s.l. over the years (IRR = 0.94, 95% CI 0.90–0.98), with the density standing at low levels of an average 0.006 mosquitoes/house in the year 2010. Conclusion Reductions in the densities of the major malaria vectors and a shift from human to animal feeding have contributed to the decreased burden of malaria along the Kenyan coast. Vector species composition remains heterogeneous but in many areas An. arabiensis has replaced An. gambiae as the major malaria vector. This has important implications for malaria epidemiology and control given that this vector predominately rests and feeds on humans outdoors. Strategies for vector control need to continue focusing on tools for protecting residents inside houses but additionally employ outdoor control tools because these are essential for further reducing the levels of malaria transmission.
Impact of insecticide-treated bed nets on malaria transmission indices on the south coast of Kenya
Francis M Mutuku, Charles H King, Peter Mungai, Charles Mbogo, Joseph Mwangangi, Eric M Muchiri, Edward D Walker, Uriel Kitron
Malaria Journal , 2011, DOI: 10.1186/1475-2875-10-356
Abstract: To evaluate the impact of the substantial increase in household bed net use within this area on vector density, vector composition, and human-vector contact, indoor and outdoor resting mosquitoes were collected in the same region during 2009-2010 using pyrethrum spray catches and clay pots for indoor and outdoor collections respectively. Information on bed net use per sleeping spaces and factors influencing mosquito density were determined in the same houses using Poisson regression analysis. Species distribution was determined, and number of mosquitoes per house, human-biting rates (HBR), and entomological inoculation rate (EIR) were compared to those reported for the same area during 1997-1998, when bed net coverage had been minimal.Compared to 1997-1998, a significant decline in the relative proportion of An. gambiae s.s. among collected mosquitoes was noted, coupled with a proportionate increase of An. arabiensis. Following > 5 years of 60-86% coverage with bed nets, the density, human biting rate and EIR of indoor resting mosquitoes were reduced by more than 92% for An. funestus and by 75% for An. gambiae s.l. In addition, the host feeding choice of both vectors shifted more toward non-human vertebrates. Besides bed net use, malaria vector abundance was also influenced by type of house construction and according to whether one sleeps on a bed or a mat (both of these are associated with household wealth). Mosquito density was positively associated with presence of domestic animals.These entomological indices indicate a much reduced human biting rate and a diminishing role of An. gambiae s.s. in malaria transmission following high bed net coverage. While increasing bed net coverage beyond the current levels may not significantly reduce the transmission potential of An. arabiensis, it is anticipated that increasing or at least sustaining high bed net coverage will result in a diminished role for An. funestus in malaria transmission.Many studies have reported the k
Influence of biological and physicochemical characteristics of larval habitats on the body size of Anopheles gambiae mosquitoes (Diptera: Culicidae) along the Kenyan coast
Joseph M. Mwangangi, Charles M. Mbogo, Ephantus J. Muturi, Joseph G. Nzovu, Ephantus W. Kabiru, John I. Githure, Robert J. Novak , John C. Beier
Journal of Vector Borne Diseases , 2007,
Abstract: Background & objectives: The number and productivity of larval habitats ultimately determine thedensity of adult mosquitoes. The biological and physicochemical conditions at the larval habitataffect larval development hence affecting the adult body size. The influence of biological and physicochemicalcharacteristics on the body size of Anopheles gambiae was assessed in Jaribuni village,Kilifi district along the Kenyan Coast.Methods: Ten cages measuring 1 × 1 × 1 m (1 m3) with a netting material were placed in 10 differentaquatic habitats, which were positive for anopheline mosquito larvae. Emergent mosquitoes werecollected daily by aspiration and the wing lengths were determined by microscopy. In the habitats,physicochemical parameters were assessed: pH, surface debris, algae and emergent plants, turbidity,substrate, nitrate, ammonia, phosphate and chlorophyll a content.Results: A total of 685 anopheline and culicine mosquitoes were collected from the emergent cages.Only female mosquitoes were considered in this study. Among the Anopheles spp, 202 were An.gambiae s.s., eight An. arabiensis, two An. funestus, whereas the Culex spp was composed of 214Cx. quinquefasciatus, 10 Cx. tigripes, eight Cx. annulioris and one Cx. cumminsii. The mean winglength of the female An. gambiae s.s. mosquitoes was 3.02 mm (n = 157), while that of An. arabiensiswas 3.09 mm (n = 9). There were no associations between the wing lengths and the environmentaland chemical parameters, except for a positive correlation between wing length of An. gambiae andchlorophyll a content (r = 0.622). The day on which the mosquitoes emerged was not significant forthe anopheline (p = 0.324) or culicine mosquitoes (p = 0.374), because the mosquito emerged fromthe cages on a daily basis.Interpretation & conclusion: In conclusion, there was variability in production of emergent mosquitoesfrom different habitats, which means that there should be targeted control on these habitatsbased on productivity.
Survival of immature Anopheles arabiensis (Diptera: Culicidae) in aquatic habitats in Mwea rice irrigation scheme, central Kenya
Joseph M Mwangangi, Ephantus J Muturi, Josephat Shililu, Simon M Muriu, Benjamin Jacob, Ephantus W Kabiru, Charles M Mbogo, John Githure, Robert Novak
Malaria Journal , 2006, DOI: 10.1186/1475-2875-5-114
Abstract: Horizontal life tables were constructed for immatures in semi-field condition. The time spent in the various immature stages was determined and survival established. Vertical life tables were obtained from five paddies sampled by standard dipping technique.Pre-adult developmental time for An. arabiensis in the trays in the experimental set up in the screen house was 11.85 days from eclosion to emergence. The mean duration of each instar stage was estimated to be 1.40 days for first instars, 2.90 days for second instars, 1.85 days for third instars, 3.80 days for fourth instars and 1.90 days for pupae. A total of 590 individuals emerged into adults, giving an overall survivorship from L1 to adult emergence of 69.4%. A total of 4,956 An. arabiensis immatures were collected in 1,400 dips throughout the sampling period. Of these, 55.9% were collected during the tillering stage, 42.5% during the transplanting period and 1.6% during the land preparation stage. There was a significant difference in the An. arabiensis larval densities among the five stages. Also there was significant variation in immature stage composition for each day's collection in each paddy. These results indicate that the survival of the immatures was higher in some paddies than others. The mortality rate during the transplanting was 99.9% and at tillering was 96.6%, while the overall mortality was 98.3%.The survival of An. arabiensis immatures was better during the tillering stage of rice growth. Further the survival of immatures in rice fields is influenced by the rice agronomic activities including addition of nitrogenous fertilizers and pesticides. For effective integrated vector management, the application of larvicides should target An. arabiensis larvae at the tillering stage (early vegetative stage of rice) when their survival in the aquatic habitats is high to significantly reduce them and the larvicides should be long-lasting to have a significant impact on the malaria vector productivity on
Spatially targeting Culex quinquefasciatus aquatic habitats on modified land cover for implementing an Integrated Vector Management (IVM) program in three villages within the Mwea Rice Scheme, Kenya
Benjamin G Jacob, Josephat Shililu, Ephantus J Muturi, Joseph M Mwangangi, Simon M Muriu, Jose Funes, John Githure, James L Regens, Robert J Novak
International Journal of Health Geographics , 2006, DOI: 10.1186/1476-072x-5-18
Abstract: Total LULC change between 1988–2005 was 42.1 % in Kangichiri, 52.8 % in Kiuria and and 50.6 % Rurumi. The most frequent LULC changes was rice field to fallow and fallow to rice field. The proportion of aquatic habitats positive for Culex larvae in LULC change sites was 77.5% in Kangichiri, 72.9% in Kiuria and 73.7% in Rurumi. Poorly – irrigated grid cells displayed 63.3% of aquatic habitats among all LULC change sites.We demonstrate that optical remote sensing can identify rice cultivation LULC sites associated with high Culex oviposition. We argue that the regions of higher Culex abundance based on oviposition surveillance sites reflect underlying differences in abundance of larval habitats which is where limited control resources could be concentrated to reduce vector larval abundance.The "focal" nature of arboviruses suggests that there are inherent landscape factors underlying the timing and distribution of transmission [1]. Human-induced land use land cover (LULC) changes are the primary drivers of a range of arbovirus disease outbreaks and emergence events and also modifiers of the transmission of endemic infections [2]. LULC changes in a rice-village ecosystem include road construction, wetland modification, agricultural encroachment, dam building, irrigation, and other activities. These changes in turn cause a cascade of factors that exacerbate infectious diseases in African ricelands caused by Culex mosquitoes [3] such as West Nile Virus (WVN), Rift Valley Fever (RVF), Yellow fever and Bancroftian filariasis[4]. For example, an increase in soil moisture associated with irrigation development in the southern Nile Delta, following the construction of the Aswan High Dam, caused a rapid rise in Cx. quinquefasciatus, and consequential increase in the arthropod-borne disease, Bancroftian filariasis [5,6]. In settlements of the Kenya Coast, Cx. pipens was found to be a very potent vector of Wuchereria bancrofti filariasis which developed in three major types of ur
Anopheles larval abundance and diversity in three rice agro-village complexes Mwea irrigation scheme, central Kenya
Joseph M Mwangangi, Josephat Shililu, Ephantus J Muturi, Simon Muriu, Benjamin Jacob, Ephantus W Kabiru, Charles M Mbogo, John Githure, Robert J Novak
Malaria Journal , 2010, DOI: 10.1186/1475-2875-9-228
Abstract: 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.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.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.Irrigation development projects have been ass
Remote and field level quantification of vegetation covariates for malaria mapping in three rice agro-village complexes in Central Kenya
Benjamin G Jacob, Ephantus J Muturi, Joseph M Mwangangi, Jose Funes, Erick X Caamano, Simon Muriu, Josephat Shililu, John Githure, Robert J Novak
International Journal of Health Geographics , 2007, DOI: 10.1186/1476-072x-6-21
Abstract: The resultant VI uncertainties did not vary from surface reflectance or atmospheric conditions. Logistic regression analyses of all field sampled covariates revealed emergent vegetation was negatively associated with mosquito larvae at the three study sites. In addition, floating vegetation (-ve) was significantly associated with immature mosquitoes in Rurumi and Kiuria (-ve); while, turbidity was also important in Kiuria. All spatial models exhibit positive autocorrelation; similar numbers of log-counts tend to cluster in geographic space. The spectral reflectance from riceland habitats, examined using the remote and field stratification, revealed post-transplanting and tillering rice stages were most frequently associated with high larval abundance and distribution.NDVI, SAVI and ARVI generated from QuickBird data and field sampled vegetation covariates modeled cannot identify highly productive riceland An. arabiensis aquatic habitats. However, combining spectral reflectance of riceland habitats from QuickBird and field sampled data can develop and implement an Integrated Vector Management (IVM) program based on larval productivity.Prediction of vegetation index (VI) associated with vector larval habitats in malaria endemic areas can be remarkably accurate [1-3]. A VI is a dimensionless, radiation-based measurement computed from spectral combinations of remotely sensed data [4]. It is used to infer vegetation properties by isolating the attributes of vegetation from other materials (e.g., soil or water). The appeal of a VI is its simplicity and its relationship either empirically or theoretically to biophysical variables [5]. VI's have been proven to be well correlated with various vegetation parameters such as green biomass [6], chlorophyll concentration [7], leaf area index (LAI) [8], foliar loss and damage [9], photosynthetic activity [10], and carbon fluxes [11]. Also, they have been found to be useful for different image analyses like crop classification [12]
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