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Josphat C. Matasyoh,Euty M. Wathuta,Samuel T. Kariuki,Regina Chepkorir 한국응용곤충학회 2011 Journal of Asia-Pacific Entomology Vol.14 No.1
Hydro-distilled essential oil from Kenyan Piper capense (Piperaceae) was analysed by gas chromatography mass spectrometry (GC–MS) and evaluated for larvicidal activity against the malaria vector, Anopheles gambiae. The oil consisted mainly of sesquiterpene hydrocarbons which accounted for 43.9% of the oil. The major sesquiterpenes were δ-cadinene (16.82%), β-bisabolene (5.65%), and bicyclogermacrene (3.30%). The oil also had appreciable amounts of monoterpene hydrocarbons (30.64%), including β-pinene (7.24%) and α-phellandrene (4.76%), and arylpropanoids (8.64%), including myristicin (4.26%). The oil showed larvicidal activity against third instar larvae of A. gambiae, with LC_50 and LC_90 values of 34.9 and 85.0 ppm, respectively. Most of the larvae died within the first few hours. The high larvicidal activity of this oil was indicated by the fact that over 80% mortality was observed at a concentration of 100 ppm after 24 h. These results compared favourably with the commercial larvicide pylarvex® which had LC_50 and LC_90 values of 3.7 and 7.8 ppm,respectively. Application of this oil or of products derived from it to larval habitats may lead to promising results in malaria and mosquito management programmes
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Evidence for several waves of global transmission in the seventh cholera pandemic
Mutreja, Ankur,Kim, Dong Wook,Thomson, Nicholas R.,Connor, Thomas R.,Lee, Je Hee,Kariuki, Samuel,Croucher, Nicholas J.,Choi, Seon Young,Harris, Simon R.,Lebens, Michael,Niyogi, Swapan Kumar,Kim, Eun J Nature Publishing Group, a division of Macmillan P 2011 Nature Vol.477 No.7365
Vibrio cholerae is a globally important pathogen that is endemic in many areas of the world and causes 3??5??million reported cases of cholera every year. Historically, there have been seven acknowledged cholera pandemics; recent outbreaks in Zimbabwe and Haiti are included in the seventh and ongoing pandemic. Only isolates in serogroup O1 (consisting of two biotypes known as ??classical?? and ??El Tor??) and the derivative O139 (refs 2, 3) can cause epidemic cholera. It is believed that the first six cholera pandemics were caused by the classical biotype, but El Tor has subsequently spread globally and replaced the classical biotype in the current pandemic. Detailed molecular epidemiological mapping of cholera has been compromised by a reliance on sub-genomic regions such as mobile elements to infer relationships, making El Tor isolates associated with the seventh pandemic seem superficially diverse. To understand the underlying phylogeny of the lineage responsible for the current pandemic, we identified high-resolution markers (single nucleotide polymorphisms; SNPs) in 154 whole-genome sequences of globally and temporally representative V.??cholerae isolates. Using this phylogeny, we show here that the seventh pandemic has spread from the Bay of Bengal in at least three independent but overlapping waves with a common ancestor in the 1950s, and identify several transcontinental transmission events. Additionally, we show how the acquisition of the SXT family of antibiotic resistance elements has shaped pandemic spread, and show that this family was first acquired at least ten years before its discovery in V.??cholerae.
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