Browsing by Author "Kweka, Eliningaya J."
Now showing 1 - 7 of 7
Results Per Page
Sort Options
Item Activity of Cinnamomum Osmophloeum Leaf Essential Oil Against Anopheles Gambiae s.s(BioMed Central, 2014) Mdoe, France P.; Cheng, Sen-Sung; Msangi, Shandala; Nkwengulila, Gamba; Chang, Shang-Tzen; Kweka, Eliningaya J.The increasing status of insecticide resistant mosquitoes in sub-Saharan Africa is a threatening alert to the existing control efforts. All sibling species of An. gambiae complex have evolved insecticide resistance in wild populations for different approved classes of the insecticides currently in use in the field. An alternative compound for vector control is absolutely urgently needed. In this study, the larvicidal activity and chemical composition of the Cinnamomum osmophloeum leaf essential oils were investigated. C. osmophloeum leaf essential oils were extracted by hydrodistillation in a Clevenger-type apparatus for 6 hours, and their chemical compositions identified using GC-MS. These oils were evaluated against An. gambiae s.s. in both laboratory and semi-field situations. The WHO test procedures for monitoring larvicidal efficacy in malaria vectors were used. The composition of C. osmophloeum leaf essential oil has been found to have 11 active compounds. The most abundant compound was trans-cinnamaldehyde (70.20%) and the least abundant was caryophyllene oxide (0.08%). The larvicidal activity was found to be dosage and time dependant both in laboratory and semi-field environments with mortality ranging from 0% to 100%. The LC50 value was found to vary from 22.18 to 58.15 μg/ml in the laboratory while in semi-field environments it was 11.91 to 63.63 μg/ml. The LC90 value was found to range between 57.71 to 91.54 μg/ml in the laboratory while in semi-field environments was 52.07 to 173.77 μg/ml. Mortality ranged from 13% to 100% in the laboratory while in semi-field environments it ranged between 43% to 100% within mortality recording time intervals of 12, 24, 48, and 72 hours. The larvicidal activity shown by C. osmophloeum leaf essential oil is a promising alternative to existing larvicides or to be incorporated in integrated larval source management compounds for An. gambiae s.s control. The efficacy observed in this study is attributed to both major and minor compounds of the essential oils.Item Characterization of Salmonella Species from Water Bodies in Dar-Es-Salaam City, Tanzania(2013) Mwang’onde, Beda J.; Tibuhwa, Donatha D.; Namkinga, Lucy A.; Kweka, Eliningaya J.Water-borne diseases are the most common cause of illness and death among the poor population from developing countries. The majority of the people are inadequately aware that aquatic environment is a major source of salmonellosis. Dar es Salaam city is among the cities with most of its population live in squatter. Typhoid fever ranks second with 14.3% of all notifiable disease cases in the city. The city experience water scarcity which forces water wells and rivers to become the main sources of water for domestic use and livestock. This study therefore, characterized Salmonella strains from different water bodies of city as possible sources for enteric diseases endemicity. Methods: The Salmonella Chromogenic Agar (SC Agar) and Kligler Iron Agar (KIA) media were used for isolation and enumeration of the strains. The inoculated cultures were incubated at 370 C for 24 hours. Salmonella colonies were confirmed by magenta colorations and hydrogen sulfide production on SC Agar and KIA Agar, respectively. The Analytical Profile Index 20 Enterobacteriaceae kit (API 20E kit) was used to identify Salmonella species. Results: Based on the API 20E kit, the identified Salmonella species from different water bodies were Salmonella ser. paratyphi A (96.9%), Salmonella cholelaesuis spp choleraesuis (99.5%) and Salmonella typhi (99.9%). Conclusion: This study shows that shallow wells and rivers which are mainly used by the city dwellers were highly contaminated with Salmonella and were more contaminated than deep wells and marine water bodies. This warrants further investigation on the disease mapping in the urban and peri-urban areas.Item Direct and Indirect Effect of Predators on Anopheles Gambiaesensu Stricto(Elsevier, 2015) Chobua, Mariam; Nkwengulila, Gamba; Mahande, Aneth M.; Mwang’onde, Beda J.; Kweka, Eliningaya J.The increased insecticides resistance by vectors and the ecological harm imposed by insecticides to beneficial organisms drawback mosquitoes chemical control efforts. Biological control would reduce insecticides tolerance and yet biodiversity friend. The predatory and non-predatory effects of Gambusia affinis and Carassius auratus on gravid Anopheles gambiae sensu strict and larvae survivorship were assessed. In determining predation rate, a single starved predator was exposed to third instar larvae of An. gambiae s.s. in different densities 20, 60 and 100. Six replicates in each of the densities for both predators, G. affinis and C. auratus, were set up. The larvae densities were monitored in every12 and 24 h. In assessing indirect effects: An. gambiae s.s. first instar larvae of three densities 20, 60 and 100 were reared in water from a predator habitat and water from non-predator habitat. Larvae were monitored until they emerged to adults where larval survivorship and sex ratio (Female to total emerged mosquitoes) of the emerged adult from both water habitats were determined. Oviposition preference: twenty gravid females of An. gambiae s.s. were provided with three oviposition choices, one containing water from predator habitat without a predator, the second with water from a predator with a predator and the third with water from non-predatory habitat. The number of eggs laid on each container was counted daily. There were 20 replicates for each predator, G. affinis and C. auratus. Survivorship of An. gambiae s.s. larvae reared in water from non-predator habitat was higher than those reared in water from the predator habitats. Many males emerged in water from non-predatory water habitats while more females emerged from predator's habitats water. More eggs laid in tap water than in water from predator habitat and water from predator habitat with live predator. In 24 h, a starved C. auratus and G. affinis were able to consume 100% of the 3rd instar larvae. The findings from this study suggest that G. affinis and C. auratus may be useful in regulating mosquito populations in favour of beneficial insects. However, a small scale trial shall be needed in complex food chain system to ascertain the observed predation and kairomones effects.Item Evaluation of Repellents Efficacy against Anopheles Gambiae s.s.; An Anthropophilic Malaria Vector(2015) Katunzi, Gerald; Munga, Stephen; Nkwengulila, Gamba; Kweka, Eliningaya J.; Matias, Jonathan R.; Godfrey, Gilbert M.Reduction of human-vector contact is of epidemiological importance in malaria control. Repellents can be used to complement the existing intervention tools against malaria vectors. Thus, evaluation of efficacy of additional mosquito repellents and /or attractants is of great significance for personal protection tools against malaria vectors. This study evaluated the repellence efficacy of menthol-propylene-glycol-carbonate (MR08) and Lemon grass (LG) against Anopheles gambiae. Experiments were performed in a room which was 7.8 meters by 3.9 meters in dimension. Three experimental set ups were performed, i) comparison of 10 hours worn sock and unworn sock; ii) comparison of 10 hours worn sock treated with MR08 against worn sock alone, and iii) comparison of 10 hours worn sock treated with LG against worn sock alone. CDC miniature light traps were used to evaluate the recovery of released mosquitoes using both repellents and attractants. After initial trials, a concentration of 500 ppm was selected for all repellents. Among 1800 mosquitoes released into the experimental room, 1230 were recovered by CDC light traps while the remaining 570 were found within the experimental room. Among those collected by light traps, 1185 were collected by traps with worn sock alone. A worn sock treated with either MR08 or Lemon grass significantly repelled An.gambiae compared to worn sock alone. The findings of this study demonstrate that MR08 and lemon grass have inhibition efficiency against mosquito stings but further field evaluations are required for observed findings against wild populations of An.gambiae at lower Moshi using slow release methodItem Larvicidal Effect of Disinfectant Soap on Anopheles Gambiae s.s (Diptera: Culicidae) in Laboratory and Semifield Environs(BioMed Central, 2014) Mdoe, France P.; Nkwengulila, Gamba; Chobua, Mariam; Lyaruu, Lucile; Gyunda, Israel L.; Mbepera, Saada; Xue, Rui-De; Kweka, Eliningaya J.Background: Mosquito larval control using chemicals and biological agents is of paramount importance in vector population and disease incidence reduction. A commercial synthetic disinfectant soap was evaluated against larvae of Anopheles gambiae s.s. in both laboratory and semi field conditions. Method: Five concentrations of commercial synthetic disinfectant soap (0.0001, 0.001, 0.01, 0.1 and 1%) were prepared and evaluated against third instar larvae in laboratory and semi field environments. Mortality was scored at 12, 24, 48, and 72 hrs. Each dosage had 6 replicates, having twenty 3rd instar larvae of An.gambiae s.s. Results: In the laboratory phase, all dosages had significantly higher larval mortalities than in controls, while in semi field conditions, the dosages of 0.0001, 0.001 and 0.01% had lower mortalities than laboratory trials. In the comparison between semi field and laboratory trials, only 0.1 and 1% dosage had significant difference with more mortality in semifield conditions. Proportions of larvae that died during mortality monitoring intervals in laboratory and semi field had significant differences only at 12 hrs and 72 hrs. Conclusion: The findings of this study have demonstrated that the mortality of larvae caused by commercial synthetic disinfectant soap is worth further studies in open water bodies. More studies are necessary to find out the effect of sunlight on the chemistry of the synthetic disinfectant and other variables in small scale full field trials. Keywords: Anopheles gambiae s.s, Larvicidal, Semi field, Laboratory, MicrocosmsItem Larvicidal Efficacy of Cryptomeria Japonica Leaf Essential Oils against Anopheles Gambiae(BioMed Central, 2014) Mdoe, France P.; Cheng, Sen-Sung; Lyaruu, Lucile; Nkwengulila, Gamba; Chang, Shang-Tzen; Kweka, Eliningaya J.Alternative insecticidal compounds with mortality effect against mosquito life cycle stages are currently needed. The compounds should be biodegradable and nontoxic to non-targeted insects. Plant based larvicides provide effective control of vector populations. This study explored Cryptomeria japonica leaf essential oil larvicidal potency against Anopheles gambiae sensu stricto. Essential oils (12.5 to 200 μg/mL) extracted from C. japonica leaves were evaluated against An. gambiae s. s. larvae in both the laboratory and semi field in 6 replicates for each dose. Larval mortality readings were taken at 12, 24, 48, and 72 h post treatment. C. japonica leaf essential oil yield was 17.06 ± 0.56 mL/kg and 1.60 ± 0.33% (w/w). GC-FID and GC-MS analyses revealed 22 constituents. Essential oil was more effective against An. gambiae s.s. larvae in the laboratory than in semi field trials. Mortality increased with increasing dosages (12.5 to 200 μg/mL) in the laboratory (31.75 to 100%) and semi field trials (17.75 to 99.5%), respectively. The LC50 value ranged from 5.55 to 63.92 μg/mL in the laboratory, and 8.22 to 134.84 μg/mL in semi field conditions, LC90 value ranged from 41.34 to 205.93 μg/mL in the laboratory and 50.92 to 213.11 μg/mL in semi field conditions. This study has demonstrated the potential of C. japonica leaf essential oil to cause mortality effects to An. gambiae s. s. larval populations, however, further studies need to be conducted under field conditions and also with individual active compounds of C. japonica essential oil.Item Reduced Hatchability of Anopheles Gambiae S.S Eggs in Presence of Third Instar Larvae(2014) Godfrey, Gilbert M.; Urasa, Fausta M.; Katunzi, Gerald; Yarro, Jacob G.; Munga, Stephen; Kweka, Eliningaya J.Background: We investigated the hatchability rates of freshly laid Anopheles gambiae s.s. eggs in presence of thirdinstars larvae. These experiments were conducted using 30 eggs in larval densities of 20, 60 and 100 larvae inmicrocosms. These experiments were designed to evaluate the eggs hatchability in habitats with late larvae instarsof the same species (experimental) or no larvae at all (control). Freshly laid eggs of An.gambiae s.s. were washed inmicrocosms containing larvae of third instars in different three densities (20, 60 and 100) and likewise in controlmicrocosms (without larvae). Eggs hatchability was monitored twice daily until no more first instar larvae emerged.The numbers of first instars larvae were record ed daily and lost eggs were considered preyed upon by third instars.Findings: The findings of this study showed that egg hatchability was significantly influence d by larval density.Conclusion: The findings of this study suggest that presence of larvae in habitats may significantly reducehatchability of eggs.