PURSE 2013

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Browsing PURSE 2013 by Subject "Aedes aegypti"

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    Absence of dengue virus NS 1 Antigen in Aedes aegypti and Aedes albopictus mosquitoes collected from urban areas of Peradeniya and Kegalle
    (The University of Peradeniya, 2013-07-04) Ekiriyagala, W. R. S. K.; Noordeen, F.; Abeykoon, A. M. S. B.; Ariyaratne, C. S.
    Dengue fever (DF) is an important mosquito-borne disease that affects humans causing morbidity and mortality. With neither vaccines nor treatment available, prevention of the disease relies heavily on surveillance and control of mosquito vectors. Aedes aegypti is considered to be the major vector for dengue virus (DENV) transmission, whereas Aedes albopictus is considered to be the secondary vector. Both Aedes spp. are responsible for carrying any of the four serotypes of DENVs (DENV1, DENV2, DENV3, and DENV4). Firstly, we examined the Aedes mosquitoes collected outdoors to identify which of the Aedes species was abundant in the urban areas of Kegalle and Peradeniya. Secondly, we evaluated NS1 antigen detection (SD BIOLINE Dengue NS1 test) in field caught Aedes aegypti and Aedes albopictus mosquitoes (n=165) to gather evidence for DENV carriage. Aedes albopictus was more abundant (115/165; 70%) than Aedes aegypti (50/165;30%) in the urban areas of Kegalle and Peradeniya. However, we were unable to detect Dengue NS1 antigen in the field caught Aedes aegypti and Aedes albopictus mosquitoes. The reason for not detecting the Dengue NS1 Ag in the field caught Aedes spp. May be twofold. First, these field caught mosquitoes may not be carrying the DENV or our test was unable to detect the low level of DENV found in the field- caught mosquito pools. However, supernatants obtained from the same mosquito pools that were tested for Dengue NS1 antigen are stored at -80oC for DENV RNA extraction and RT-PCR to confirm the validity of Dengue NS1 antigen detection test in the field caught mosquitoes.
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    The efficacy of polydimethylsiloxane (aquatain) mosquito formulation on the immature stages of Aedes aegypti (primary vector of dengue) and non-target organism poecilia reticulate (GUPPY)
    (The University of Peradeniya, 2013-07-04) Mudalige, Malka P. S.; Kusumawathie, P.; Jayasooriya, G. A. J. S. K.
    Polydimethylsiloxane (Aquatain), a silicon based compound which produces a monomolecular surface film has been proposed and investigated as a potential mosquito control agent, reducing water surface tension and restricting the ability of mosquito larvae to attach respiratory tube to the water surface. The main objective of this study was to evaluate the efficacy of Aquatain Mosquito Formulation (AMF) on immature stages of primary vector of dengue, Aedes aegypti and the fish Poecillia reticulate (guppy) under laboratory conditions. Several replicates of different immature stages of field collected Ae.aegypti were exposed to and AMF and the mortalities were observed for 5-7 days. Early stages of Aedes aegypti larvae obtained from eggs collected using ovitraps were introduced to AMF to determine the mortality and further development for 15 days. Six experimental tanks with ten healthy guppies were also treated with AMF and monitored daily for a month to assess the toxicity effect on guppy. All these experiments were carried out as case-control studies. Mortalities on day 1 for late and early larvae with concentration were 75% (n=100) and 0% (n=50) while day 5 mortalities were 84% and 14% respectively. Mortalities on day 1 for late and early larvae with concentration were 59% (n=100) and 64% (n=50) while the day 5 mortalities were 71% and 74% respectively. 100% pupal mortality was observed within 24 hours of exposure to AMF. The experiment with early larvae exposed to for 15 days duration (n=80) verified the mortality of 3.8% on day 1 and 98.8% on day 15. In control experiments, pupation was initiated on day 5 and adults emerged on day 6 onwards. None of the treated larvae were pupated within 15 days, however only one larva (1.25%) developed into mature larvae after 8 days of exposure. None of the fish exposed to AMF or in control tanks were dead even after one month. While 100% immediate pupal mortality of Aedes aegypti was achieved the larval mortality was 71 -74% after one week of exposure. A significant retardation of larval development and delayed mortality of early stage larvae after exposure to AMF show that polydimethylsiloxane can be used as an effective control agent against the primary vector of dengue under laboratory conditions. AMF can be recommended as the effective dosage on all immature stages of Aedes aegypti.