College of Natural and Applied Sciences

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Browsing College of Natural and Applied Sciences by Author "Abdulla, Salim"

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    Diversity, Spatial and Temporal Abundance of Anopheles Gambiae Complex in the Rufiji River Basin, South-Eastern Tanzania
    (2010) Nkwengulila, Gamba; Magesa, S. M.; Abdulla, Salim; Kigadye, E. S. P.
    The Anopheles gambiae complex contains the most efficient malaria vectors in the world. Identification of the species and the concomitant distribution are vital for effective malaria control. The objective of the study was to establish the diversity, spatial and seasonal abundance of malaria vectors in the Rufiji River Basin in Tanzania and the implications on malaria vector control. Mosquitoes were collected using CDC light-traps. Anopheles mosquitoes were identified by conventional keys. Anopheles gambiae complex were speciated using standard PCR method. Of the 562 specimens analysed by PCR 69% produced fragments equivalent to An. gambiae s.s. (390 bp), 23% equivalent to An. arabiensis (315bp), and 7% as An. merus (464 bp). An. gambiae s.s. and An. merus were more abundant on the plateau than on the flood plain (Fisher’s exact test, P< 0001), whereas An. arabiensis was equally abundant between the two sites (Fisher’s exact test, P=1656). The density of the three sibling species of An. gambiae complex also varied with the seasons. An. gambiae s.s. and An. arabiensis were most predominant species during the start of the rainy season, but as season progresses, An. gambiae s.s. predominated. An. merus was only recorded during the short rainy season. In conclusion, both An. gambiae s.s., An. arabiensis and An.merus are malaria vectors in the Rufiji River basin and that An. merus is recorded for the first time in the south-eastern coast of Tanzania. These findings are important in the planning and implementation of malaria vector control activities in the Rufiji River basin, south-eastern Tanzania.
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    Genetic Diversity of Plasmodium falciparum Strains in Children under Five Years of Age in Southeastern Tanzania
    (2010) Sumari, Deborah; Hosea, Ken M.; Mugasa, Joseph P.; Abdulla, Salim
    Strain diversity may play a role in delaying development of protective immunity in endemic areas. We evaluated genetic diversity of Plasmodium falciparum infected children before being treated with Sulphadoxine Pyrimethamine (SP) and Coartem™ in Southeastern Tanzania. Allelic diversity of P. falciparum strains were determined in order to further assist in correct estimation of recrudescent and new infections. P. falciparum isolated from 300 children aged 1-59 months was used in the study, where nested PCR followed by Restriction Fragment Length Polymorphism (RFLP) of highly polymorphic Merozoite surface protein 2 (msp2) was employed to understand the genetic diversity of the parasites population. Frequency of msp2 gene alleles was calculated and further associated with multiplicity of infection of children under five years of age. A total of 71 and 83 different msp2 alleles were found in Rufiji and Ulanga districts respectively. Children infected with either FC27 or 3D7 allelic type in Rufiji were 42% single, 55.3% double and 2.7% triple, while in Ulanga, 36.7% single, 62% double and 1.3% triple infections. Mean numbers of multiplicity of infections (MOI) in Rufiji and Ulanga were 1.6 and 1.3, respectively. These findings show a high genetic diversity of P. falciparum strains in study areas and low MOI could reflect production of susceptible parasites that immune response can accommodate or can be cleared by the drugs. Furthermore, 3D7 allelic type of msp2 gene was more prevalent than FC27 in Ulanga district, indicating association between msp2 allelic type and disease severity, hence predict possible vaccine candidate in the future.
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    Investigations on Risk Factors for Malaria in Rufiji District, Tanzania
    (2013) Kigadye, E. S. P.; Nkwengulila, Gamba; Magesa, S.; Abdulla, Salim
    Rufiji District is an area with endemic and perennial malaria. The aim ofthis study was to assess the factors contributing to increased malaria risk in thestudy area. The factors investigated included; mode of house construction,protection against mosquito bites and human behaviour. Parameters recorded forevaluating the mode of house construction were; type of wall, roofing materials,presence of open eaves between wall and roof and the type of window. Structuredquestionnaires were used to assess household mosquito avoidance behaviour andutilization of bed nets. Medium scale behavioural surveys were carried out todetermine time spent by individuals outdoors during the night. This was then plottedagainst mean hourly mosquito catches. Generally, house constructed using mud,grass, palm walls, and roofs made of grass/palm thatch, houses with no or openwindows and without mosquito gauze and houses with open eaves and lowutilization of bed nets (treated and untreated) were common over the entire studyarea. Of the 2,423 houses walls examined; 90% were constructed using mud, 61%were roofed using grass, 98% had eaves between wall and roof, and 49% had nowindows while 45% of windows had no mosquito gauzes. There were highlysignificant differences (p < 0.001) within all the above variables investigated. Only21% of the households used bed nets of which only 7.5% were insecticides treated.There were highly significant differences (p < 0.0001) within variables investigatedon mosquito avoidance behaviour. Most individuals, both children and adults,remained outdoors up to 22.00 hrs. Environmental factors, poorly constructedhouses, low rate of utilization of bed nets and other protective measures, andpoverty were identified as risk determinants for malaria in the study area.Intervention measures relevant to the study area are discussed.
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    Spatial Variability in the Density, Distribution and Vectorial Capacity of Anopheline Species in a High Transmission District in Tanzania
    (2011) Kigadye, Emmanuel; Nkwengulila, Gamba; Magesa, Stephen M.; Abdulla, Salim
    Malaria transmission varies from one area to another and there are also local difference in time and space. The objective of the study was to determine the local variability of entomological parameters namely, mosquito abundance, human biting rate (HBR), sporozoite rate for Plasmodium falciparum and entomological inoculation rate (EIR). The study was carried out in Rufiji District south eastern Tanzania from October 2001 and September 2004. Adult mosquitoes were collected indoors by CDC light traps. PCR was employed to identify the species within the Anopheles gambiae complex. ELISA was used to determine the sporozoite rate. Over a three year sampling period a total of 64,875 female mosquitoes were caught using light-traps, and of these 28% were Anopheles gambiae complex, 25% An. funestus Giles, 1% An. pharoensis Theobald, 46% Culex species and the rest were Mansonia uniformis Theobald. Mosquito abundance and species composition varied seasonally, spatially and between years. Using PCR, three members of the Anopheles gambiae complex namely An. gambiae s.s. Giles (69%), An. arabiensis Paton (23%) and An. merus Dönitz (7%) were confirmed to occur in the study area. Plasmodium falciparum circumsporozoite antigen (CSA) rates were 3.5% for An. gambiae complex and 2.3% for An. funestus. The mean EIR ranged from 28-275 infective bites/person/year. Transmission indices varied over short distances, seasonally and between years. In conclusion, malaria transmission indices in the study area are one of the highest in Tanzania; and there is high variability of entomological parameters over a small geographical area.