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Search Results: 1 - 10 of 863 matches for " Musa Jawara "
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Status of insecticide susceptibility in Anopheles gambiae s.l. from malaria surveillance sites in The Gambia
Martha Betson, Musa Jawara, Taiwo Awolola
Malaria Journal , 2009, DOI: 10.1186/1475-2875-8-187
Abstract: Anopheles larvae were collected from six malaria surveillance sites (Brikama, Essau, Farafenni, Mansakonko, Kuntaur and Basse) established by the National Malaria Control Programme and the UK Medical Research Council Laboratories in The Gambia. The mosquitoes were reared to adulthood and identified using morphological keys and a species-specific polymerase chain reaction assay. Two- to three-day old adult female mosquitoes were tested for susceptibility to permethrin, deltamethrin and DDT using standard WHO protocols, insecticide susceptibility test kits and treated papers.All Anopheles mosquitoes tested belonged to the Anopheles gambiae complex. Anopheles arabiensis was predominant (54.1%), followed by An. gambiae s.s. (26.1%) and Anopheles melas (19.8%). Anopheles gambiae s.s. and An. arabiensis were found at all six sites. Anopheles melas was recorded only at Brikama. Mosquitoes from two of the six sites (Brikama and Basse) were fully susceptible to all three insecticides tested. However, DDT resistance was found in An. gambiae from Essau where the 24 hours post-exposure mortality was <80% but 88% for permethrin and 92% for deltamethrin.This current survey of insecticide resistance in Anopheles provides baseline information for monitoring resistance in The Gambia and highlights the need for routine resistance surveillance as an integral part of the proposed nation wide IRS intervention using DDT.Malaria vector control, using either insecticide-treated nets (ITNs) or indoor residual spraying (IRS), relies on the continued susceptibility of Anopheles mosquitoes to a limited number of insecticides. Twelve insecticides from four classes (organochlorines, organophosphates, carbamates and pyrethroids) have been recommended for IRS [1,2], but only pyrethroids have been approved for treating bed nets. Since the mid-1950s, there have been numerous reports of reduced Anopheles susceptibility to DDT, malathion, fenithrotion, propoxur and bendiocarb, and resistance to all fo
Reduction of Malaria Transmission to Anopheles Mosquitoes with a Six-Dose Regimen of Co-Artemether
Sutherland Colin J,Ord Rosalynn,Dunyo Sam,Jawara Musa
PLOS Medicine , 2005, DOI: 10.1371/journal.pmed.0020092.20050521
Abstract: Background Resistance of malaria parasites to chloroquine (CQ) and sulphadoxine-pyrimethamine (SP) is increasing in prevalence in Africa. Combination therapy can both improve treatment and provide important public health benefits if it curbs the spread of parasites harbouring resistance genes. Thus, drug combinations must be identified which minimise gametocyte emergence in treated cases, and so prevent selective transmission of parasites resistant to any of the partner drugs. Methods and Findings In a randomised controlled trial, 497 children with uncomplicated falciparum malaria were treated with CQ and SP (three doses and one dose respectively; n = 91), or six doses of artemether in fixed combination with lumefantrine (co-artemether [Coartem, Riamet]) (n = 406). Carriage rates of Plasmodium falciparum gametocytes and trophozoites were measured 7, 14, and 28 d after treatment. The infectiousness of venous blood from 29 children carrying P. falciparum gametocytes 7 d after treatment was tested by membrane-feeding of Anopheles mosquitoes. Children treated with co-artemether were significantly less likely to carry gametocytes within the 4 weeks following treatment than those receiving CQ/SP (30 of 378 [7.94%] versus 42 of 86 [48.8%]; p < 0.0001). Carriers in the co-artemether group harboured gametocytes at significantly lower densities, for shorter periods (0.3 d versus 4.2 d; p < 0.0001) and were less infectious to mosquitoes at day 7 (p < 0.001) than carriers who had received CQ/SP. Conclusions Co-artemether is highly effective at preventing post-treatment transmission of P. falciparum. Our results suggest that co-artemether has specific activity against immature sequestered gametocytes, and has the capacity to minimise transmission of drug-resistant parasites.
Development of Odour-Baited Flytraps for Sampling the African Latrine Fly, Chrysomya putoria, a Putative Vector of Enteric Diseases
Thomas C. Lindsay, Musa Jawara, Umberto D’Alessandro, Margaret Pinder, Steven W. Lindsay
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0050505
Abstract: African pit latrines produce prodigious numbers of the latrine fly, Chrysomya putoria, a putative vector of diarrhoeal pathogens. We set out to develop a simple, low-cost odour-baited trap for collecting C. putoria in the field. A series of field experiments was carried out in The Gambia to assess the catching-efficiency of different trap designs. The basic trap was a transparent 3L polypropylene box baited with 50 g of fish, with a white opaque lid with circular entrance holes. We tested variations of the number, diameter, position and shape of the entrance holes, the height of the trap above ground, degree of transparency of the box, its shape, volume, colour, and the attractiveness of gridded surfaces on or under the trap. Traps were rotated between positions on different sampling occasions using a Latin Square design. The optimal trapping features were incorporated into a final trap that was tested against commercially available traps. Features of the trap that increased the number of flies caught included: larger entrance holes (compared with smaller ones, p<0.001), using conical collars inside the holes (compared with without collars, p = 0.01), entrance holes on the top of the trap (compared with the side or bottom, p<0.001), traps placed on the ground (compared with above ground, p<0.001), the box having transparent sides (compared with being opaque, p<0.001), and with no wire grids nearby (compared with those with grids, p = 0.03). This trap collected similar numbers of C. putoria to other common traps for blow flies. The optimum trap design was a transparent box, with a white plastic lid on top, perforated with 10 conical entrance holes, placed on the ground. Our simple trap provides a cheap, low-maintenance and effective method of sampling C. putoria in the field.
Field Testing of Different Chemical Combinations as Odour Baits for Trapping Wild Mosquitoes in The Gambia
Musa Jawara, Taiwo S. Awolola, Margaret Pinder, David Jeffries, Renate C. Smallegange, Willem Takken, David J. Conway
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0019676
Abstract: Odour baited traps have potential use in population surveillance of insect vectors of disease, and in some cases for vector population reduction. Established attractants for human host-seeking mosquitoes include a combination of CO2 with L-lactic acid and ammonia, on top of which additional candidate compounds are being tested. In this field study in rural Gambia, using Latin square experiments with thorough randomization and replication, we tested nine different leading candidate combinations of chemical odorants for attractiveness to wild mosquitoes including anthropophilic malaria vectors, using modified Mosquito Magnet-X (MM-X) counterflow traps outside experimental huts containing male human sleepers. Highest catches of female mosquitoes, particularly of An. gambiae s.l. and Mansonia species, were obtained by incorporation of tetradecanoic acid. As additional carboxylic acids did not increase the trap catches further, this ‘reference blend’ (tetradecanoic acid with L-lactic acid, ammonia and CO2) was used in subsequent experiments. MM-X traps with this blend caught similar numbers of An. gambiae s.l. and slightly more Mansonia and Culex mosquitoes than a standard CDC light trap, and these numbers were not significantly affected by the presence or absence of human sleepers in the huts. Experiments with CO2 produced from overnight yeast cultures showed that this organic source was effective in enabling trap attractiveness for all mosquito species, although at a slightly lower efficiency than obtained with use of CO2 gas cylinders. Although further studies are needed to discover additional chemicals that increase attractiveness, as well as to optimise trap design and CO2 source for broader practical use, the odour-baited traps described here are safe and effective for sampling host-seeking mosquitoes outdoors and can be incorporated into studies of malaria vector ecology.
Airflow attenuation and bed net utilization: observations from Africa and Asia
Lorenz von Seidlein, Ikonomedis Konstantin, Rasmus Bruun, Musa Jawara, Margaret Pinder, Bart GJ Knols, Jakob B Knudsen
Malaria Journal , 2012, DOI: 10.1186/1475-2875-11-200
Abstract: The highest indoor temperatures (49.0?C) were measured in The Gambia. During the hottest months of the year the mean temperature at night (9?pm) was between 33.1?C (The Gambia) and 26.2?C (Thailand). The bed net attenuated the airflow from a minimum of 27% (Philippines) to a maximum of 71% (The Gambia). Overall the bed nets reduced airflow compared to un-attenuated airflow from 9 to 4?cm?sec-1 or 52% (p?<?0.001). In all sites, no statistically significant difference in temperature or humidity was detected between the inside and outside of the bed net. Wind tunnel experiments with 11 different mesh-sized bed nets showed an overall reduction in airflow of 64% (range 55 - 71%) compared to un-attenuated airflow. As expected, airflow decreased with increasing net mesh size. Nets with a mesh of 136 holes inch-2 reduced airflow by 55% (mean; range 51 - 73%). A denser net (200 holes inch-2) attenuated airflow by 59% (mean; range 56 - 74%).Despite concerted efforts to increase the uptake of this intervention in many areas uptake remains poor. Bed nets reduce airflow, but have no influence on temperature and humidity. The discomfort associated with bed nets is likely to be most intolerable during the hottest and most humid period of the year, which frequently coincides with the peak of malaria vector densities and the force of pathogen transmission.These observations suggest thermal discomfort is a factor limiting bed net use and open a range of architectural possibilities to overcome this limitation.
Dry season ecology of Anopheles gambiae complex mosquitoes in The Gambia
Musa Jawara, Margaret Pinder, Chris J Drakeley, Davis C Nwakanma, Ebrima Jallow, Claus Bogh, Steve W Lindsay, David J Conway
Malaria Journal , 2008, DOI: 10.1186/1475-2875-7-156
Abstract: Weekly adult mosquito collections (pyrethrum spray, light trap, and search collections from rooms, as well as light trap collections from animal shelters, abandoned wells and grain stores), and artificial sentinel breeding site surveys were performed in four villages near the upper tidal and partially saline part of the Gambia River in the last four months of an annual dry season (March to June). Mosquito species were identified by morphological and DNA analysis, and ELISA assays were performed to test for Plasmodium falciparum sporozoites and human blood meal components.Adults of An. gambiae s.l. were collected throughout the period, numbers increasing towards the end of the dry season when humidity was increasing. Adult collections were dominated by An. melas (86%), with An. gambiae s.s. (10%) and An. arabiensis (3%) also present throughout. Most females collected in room search and spray collections contained blood meals, but most from light traps were unfed. None of the females tested (n = 1709) contained sporozoites. Larvae (mostly An. gambiae s.s.) were recovered from artificial sentinel breeding sites in the two villages that had freshwater pools. These two villages had the highest proportions of An. gambiae s.s. adults, and experienced the most substantial increase in proportions of An. gambiae s.s. after the onset of rains.During the dry season population minimum, An. melas was the predominant vector species, but differences among villages in availability of fresh-water breeding sites correlate with egg laying activity and relative numbers of An. gambiae s.s. adults, and with the increase in this species immediately after the beginning of the rains. Local variation in dry season vector persistence is thus likely to influence spatial heterogeneity of transmission intensity in the early part of the rainy season.Malaria transmission in The Gambia occurs mainly within a few months of each year, due to a single rainy season from June to October which creates bre
Anopheles gambiae complex along The Gambia river, with particular reference to the molecular forms of An. gambiae s.s
Beniamino Caputo, Davis Nwakanma, Musa Jawara, Majidah Adiamoh, Ibrahima Dia, Lassana Konate, Vincenzo Petrarca, David J Conway, Alessandra della Torre
Malaria Journal , 2008, DOI: 10.1186/1475-2875-7-182
Abstract: Collections of indoor-resting An. gambiae s.l. females were carried out along a ca. 400 km west to east transect following the River Gambia from the western coastal region of The Gambia to south-eastern Senegal during 2005 end of rainy season/early dry season and the 2006 rainy season. Specimens were identified to species and molecular forms by PCR-RFLP and the origin of blood-meal of fed females was determined by ELISA test.Over 4,000 An. gambiae s.l. adult females were collected and identified, 1,041 and 3,038 in 2005 and 2006, respectively. M-form was mainly found in sympatry with Anopheles melas and S-form in the western part of the transect, and with Anopheles arabiensis in the central part. S-form was found to prevail in rural Sudan-Guinean savannah areas of Eastern Senegal, in sympatry with An. arabiensis. Anopheles melas and An. arabiensis relative frequencies were generally lower in the rainy season samples, when An. gambiae s.s. was prevailing. No large seasonal fluctuations were observed for M and S-forms. In areas where both M and S were recorded, the frequency of hybrids between them ranged from to 0.6% to 7%.The observed pattern of taxa distribution supports the hypothesis of a better adaptation of M-form to areas characterized by water-retaining alluvial deposits along the Gambia River, characterized by marshy vegetation, mangrove woods and rice cultivations. In contrast, the S-form seems to be better adapted to free-draining soil, covered with open woodland savannah or farmland, rich in temporary larval breeding sites characterizing mainly the eastern part of the transect, where the environmental impact of the Gambia River is much less profound and agricultural activities are mainly rain-dependent. Very interestingly, the observed frequency of hybridization between the molecular forms along the whole transect was much higher than has been reported so far for other areas.The results support a bionomic divergence between the M and S-forms, and suggest
Optimizing Odor-Baited Trap Methods for Collecting Mosquitoes during the Malaria Season in The Gambia
Musa Jawara,Renate C. Smallegange,David Jeffries,Davis C. Nwakanma,Taiwo Samson Awolola,Bart G. J. Knols,Willem Takken,David J. Conway
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0008167
Abstract: Baited traps are potential tools for removal or surveillance of disease vectors. To optimize the use of counter-flow traps baited with human odor (nylon socks that had been worn for a single day) to capture wild mosquitoes in the Gambia, investigations were conducted at a field experimental site.
Reduction of Malaria Transmission to Anopheles Mosquitoes with a Six-Dose Regimen of Co-Artemether
Colin J Sutherland ,Rosalynn Ord,Sam Dunyo,Musa Jawara,Christopher J Drakeley,Neal Alexander,Rosalind Coleman,Margaret Pinder,Gijs Walraven,Geoffrey A. T Targett
PLOS Medicine , 2005, DOI: 10.1371/journal.pmed.0020092
Abstract: Background Resistance of malaria parasites to chloroquine (CQ) and sulphadoxine-pyrimethamine (SP) is increasing in prevalence in Africa. Combination therapy can both improve treatment and provide important public health benefits if it curbs the spread of parasites harbouring resistance genes. Thus, drug combinations must be identified which minimise gametocyte emergence in treated cases, and so prevent selective transmission of parasites resistant to any of the partner drugs. Methods and Findings In a randomised controlled trial, 497 children with uncomplicated falciparum malaria were treated with CQ and SP (three doses and one dose respectively; n = 91), or six doses of artemether in fixed combination with lumefantrine (co-artemether [Coartem, Riamet]) (n = 406). Carriage rates of Plasmodium falciparum gametocytes and trophozoites were measured 7, 14, and 28 d after treatment. The infectiousness of venous blood from 29 children carrying P. falciparum gametocytes 7 d after treatment was tested by membrane-feeding of Anopheles mosquitoes. Children treated with co-artemether were significantly less likely to carry gametocytes within the 4 weeks following treatment than those receiving CQ/SP (30 of 378 [7.94%] versus 42 of 86 [48.8%]; p < 0.0001). Carriers in the co-artemether group harboured gametocytes at significantly lower densities, for shorter periods (0.3 d versus 4.2 d; p < 0.0001) and were less infectious to mosquitoes at day 7 (p < 0.001) than carriers who had received CQ/SP. Conclusions Co-artemether is highly effective at preventing post-treatment transmission of P. falciparum. Our results suggest that co-artemether has specific activity against immature sequestered gametocytes, and has the capacity to minimise transmission of drug-resistant parasites.
To assess whether indoor residual spraying can provide additional protection against clinical malaria over current best practice of long-lasting insecticidal mosquito nets in The Gambia: study protocol for a two-armed cluster-randomised trial
Margaret Pinder, Musa Jawara, Lamin BS Jarju, Ballah Kandeh, David Jeffries, Manuel F Lluberas, Jenny Mueller, David Parker, Kalifa Bojang, David J Conway, Steve W Lindsay
Trials , 2011, DOI: 10.1186/1745-6215-12-147
Abstract: A 2 armed cluster-randomised controlled trial will be conducted to assess whether DDT IRS and LLINs combined provide better protection against clinical malaria in children than LLINs alone in rural Gambia. Each cluster will be a village, or a group of small adjacent villages; all clusters will receive LLINs and half will receive IRS in addition. Study children, aged 6 months to 13 years, will be enrolled from all clusters and followed for clinical malaria using passive case detection to estimate malaria incidence for 2 malaria transmission seasons in 2010 and 2011. This will be the primary endpoint. Exposure to malaria parasites will be assessed using light and exit traps followed by detection of Anopheles gambiae species and sporozoite infection. Study children will be surveyed at the end of each transmission season to estimate the prevalence of Plasmodium falciparum infection and the prevalence of anaemia.Practical issues concerning intervention implementation, as well as the potential benefits and risks of the study, are discussed.ISRCTN01738840 - Spraying And Nets Towards malaria Elimination (SANTE)Although progress is being made [1], malaria remains one of the world's greatest childhood killers [2], consumes almost half of the clinical services in Africa (http://www.rbm.who.int webcite), and is a substantial obstacle to social and economic development in the tropics [3,4]. We know from historical accounts that in the 1950s and 1960s malaria was controlled using indoor residual spraying (IRS) with DDT for vector control in many parts of the tropics [5]. DDT was highly effective in reducing malaria infection, but was not used widely in Africa.Today, Roll Back Malaria is mainly concerned with reducing the burden of disease and is gathering pace. The Global Fund to fight AIDS, Tuberculosis and Malaria (http://www.theglobalfund.org webcite) and the US President's Malaria Initiative (http://www.fightingmalaria.gov webcite) are major players in malaria control and str
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