Browsing by Author "Mdoe, France P."

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    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.
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    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, Microcosms
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    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.