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      Composition and Genetic Diversity of Mosquitoes (Diptera: Culicidae) on Islands and Mainland Shores of Kenya’s Lakes Victoria and Baringo

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          Abstract

          The Lake Baringo and Lake Victoria regions of Kenya are associated with high seroprevalence of mosquito-transmitted arboviruses. However, molecular identification of potential mosquito vector species, including morphologically identified ones, remains scarce. To estimate the diversity, abundance, and distribution of mosquito vectors on the mainland shores and adjacent inhabited islands in these regions, we collected and morphologically identified adult and immature mosquitoes and obtained the corresponding sequence variation at cytochrome c oxidase 1 (COI) and internal transcribed spacer region 2 (ITS2) gene regions. A total of 63 species (including five subspecies) were collected from both study areas, 47 of which have previously been implicated as disease vectors. Fourteen species were found only on island sites, which are rarely included in mosquito diversity surveys. We collected more mosquitoes, yet with lower species composition, at Lake Baringo (40,229 mosquitoes, 32 species) than at Lake Victoria (22,393 mosquitoes, 54 species). Phylogenetic analysis of COI gene sequences revealed Culex perexiguus and Cx. tenagius that could not be distinguished morphologically. Most Culex species clustered into a heterogeneous clade with closely related sequences, while Culex pipiens clustered into two distinct COI and ITS2 clades. These data suggest limitations in current morphological identification keys. This is the first DNA barcode report of Kenyan mosquitoes. To improve mosquito species identification, morphological identifications should be supported by their molecular data, while diversity surveys should target both adults and immatures. The diversity of native mosquito disease vectors identified in this study impacts disease transmission risks to humans and livestock.

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          Identification of single specimens of the Anopheles gambiae complex by the polymerase chain reaction.

          A ribosomal DNA-polymerase chain reaction (PCR) method has been developed for species identification of individuals of the five most widespread members of the Anopheles gambiae complex, a group of morphologically indistinguishable sibling mosquito species that includes the major vectors of malaria in Africa. The method, which is based on species-specific nucleotide sequences in the ribosomal DNA intergenic spacers, may be used to identify both species and interspecies hybrids, regardless of life stage, using either extracted DNA or fragments of a specimen. Intact portions of a mosquito as small as an egg or the segment of one leg may be placed directly into the PCR mixture for amplification and analysis. The method uses a cocktail of five 20-base oligonucleotides to identify An. gambiae, An. arabiensis, An. quadriannnulatus, and either An. melas in western Africa or An. melas in eastern and southern Africa.
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            Differential Susceptibilities of Aedes aegypti and Aedes albopictus from the Americas to Zika Virus

            Background Since the major outbreak in 2007 in the Yap Island, Zika virus (ZIKV) causing dengue-like syndromes has affected multiple islands of the South Pacific region. In May 2015, the virus was detected in Brazil and then spread through South and Central America. In December 2015, ZIKV was detected in French Guiana and Martinique. The aim of the study was to evaluate the vector competence of the mosquito spp. Aedes aegypti and Aedes albopictus from the Caribbean (Martinique, Guadeloupe), North America (southern United States), South America (Brazil, French Guiana) for the currently circulating Asian genotype of ZIKV isolated from a patient in April 2014 in New Caledonia. Methodology/Principal Findings Mosquitoes were orally exposed to an Asian genotype of ZIKV (NC-2014-5132). Upon exposure, engorged mosquitoes were maintained at 28°±1°C, a 16h:8h light:dark cycle and 80% humidity. 25–30 mosquitoes were processed at 4, 7 and 14 days post-infection (dpi). Mosquito bodies (thorax and abdomen), heads and saliva were analyzed to measure infection, dissemination and transmission, respectively. High infection but lower disseminated infection and transmission rates were observed for both Ae. aegypti and Ae. albopictus. Ae. aegypti populations from Guadeloupe and French Guiana exhibited a higher dissemination of ZIKV than the other Ae. aegypti populations examined. Transmission of ZIKV was observed in both mosquito species at 14 dpi but at a low level. Conclusions/Significance This study suggests that although susceptible to infection, Ae. aegypti and Ae. albopictus were unexpectedly low competent vectors for ZIKV. This may suggest that other factors such as the large naïve population for ZIKV and the high densities of human-biting mosquitoes contribute to the rapid spread of ZIKV during the current outbreak.
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              Heat treatment prior to testing allows detection of antigen of Dirofilaria immitis in feline serum

              Background Diagnosis of Dirofilaria immitis infection in cats is complicated by the difficulty associated with reliable detection of antigen in feline blood and serum samples. Methods To determine if antigen-antibody complex formation may interfere with detection of antigen in feline samples, we evaluated the performance of four different commercially available heartworm tests using serum samples from six cats experimentally infected with D. immitis and confirmed to harbor a low number of adult worms (mean = 2.0). Sera collected 168 (n = 6), 196 (n = 6), and 224 (n = 6) days post infection were tested both directly and following heat treatment. Results Antigen was detected in serum samples from 0 or 1 of 6 infected cats using the assays according to manufacturer’s directions, but after heat treatment of serum samples, as many as 5 of 6 cats had detectable antigen 6–8 months post infection. Antibodies to D. immitis were detected in all six infected cats by commercial in-clinic assay and at a reference laboratory. Conclusions These results indicate that heat treatment of samples prior to testing can improve the sensitivity of antigen assays in feline patients, supporting more accurate diagnosis of this infection in cats. Surveys conducted by antigen testing without prior heat treatment of samples likely underestimate the true prevalence of infection in cats.
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                Author and article information

                Journal
                J Med Entomol
                J. Med. Entomol
                jme
                jmedent
                Journal of Medical Entomology
                Oxford University Press
                0022-2585
                1938-2928
                November 2016
                11 July 2016
                11 July 2016
                : 53
                : 6
                : 1348-1363
                Affiliations
                1Martin Lüscher Emerging Infectious Diseases (ML-EID) Laboratory, International Centre of Insect Physiology and Ecology, Kasarani, P. O. Box 30772-00100, Nairobi, Kenya ( yvonneuo@ 123456yahoo.com ; jandouwe@ 123456icipe.org ; domondi@ 123456icipe.org ; dsalifu@ 123456icipe.org ; ogathomas@ 123456gmail.com ; dmasiga@ 123456icipe.org )
                2Department of Botany (Genetics), Jomo Kenyatta University of Agriculture and Technology, Juja, P. O. Box 62000-00200, Nairobi, Kenya ( awmuigai@ 123456yahoo.co.uk )
                4Biochemistry and Molecular Biology Department, Egerton University, P. O. Box 536-20115, Egerton, Kenya
                5Molecular Biology and Virology Laboratory, Department of Medical Biosciences, University of Western Cape, Private Bag X17, Bellville 7535, South Africa
                6Insect Symbiosis Research Group, Max Planck Institute for Chemical Ecology (MPI-CE), Hans-Knoll Str. 8, 07745-Jena, Germany
                7Department for Evolutionary Ecology, Institute for Zoology, Johannes Gutenberg University Mainz, Johann-Joachim-Becher-Weg 13, 55128 Mainz, Germany, and
                8Invertebrates Zoology Section, National Museums of Kenya, P. O. Box 40658-00100, Museum Hill Rd., Nairobi, Kenya ( lnjoroge@ 123456museums.or.ke )
                Author notes
                3Corresponding author, e-mail: jandouwe@ 123456icipe.org
                Article
                tjw102
                10.1093/jme/tjw102
                5106823
                27402888
                4938edb9-fe95-451d-9e68-37262528320c
                © The Authors 2016. Published by Oxford University Press on behalf of Entomological Society of America.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 12 January 2016
                : 26 May 2016
                Page count
                Pages: 16
                Categories
                Sampling, Distribution, Dispersal

                mosquito-borne disease,vector ecology,genetics,culicine,anopheles

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