Medicine

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Optimization of Aedes albopictus rearing procedures for combined sterile insect techniques (SIT) and Wolbachia-based laboratory studies in Sri Lanka
(Springer Science and Business Media Deutschland GmbH, 2020) Wijegunawardana, N.D.A.D.; Gunawardene, Y.I.N.S.; Abeyewickreme, W.; Chandrasena, T.G.A.N.; Dassanayake, R.S.; Manamperi, A.
The establishment of a laboratory colony is an essential first step for conduction of laboratory studies on the biology and control of Aedes albopictus mosquitoes. Therefore, with the objective of generating high quality mosquitoes as research material for utilization in ongoing vector control studies and to disseminate authenticated, high-quality Ae. albopictus mosquito rearing information to the research community, maintenance of an Ae. albopictus mosquito colony was initiated at the Molecular Medicine Unit, Faculty of Medicine, University of Kelaniya, Sri Lanka. A self-mating colony was established from eggs of the F1 progeny of individuals collected as free-living larvae in Narahenpita (Western Province), Sri Lanka. The mean temperature of 28 °C (± 2 °C) and relative humidity of 80% (± 5%) was constantly maintained inside the insectary. Lighting was provided by fluorescent lights, regulated with 12:12 h continuous dark and light period. Pest insects were controlled manually. Mosquitoes were maintained on bovine blood provided via an artificial membrane feeding system and a continuous supply of 10% sugar supplements. Larvae were maintained in deoxygenate water and fed with International Atomic Energy Agency (IAEA) recommended diet of tuna meal, bovine liver powder, and brewery yeast in a ratio of 37.5:27:10.5 in 1 L. Data on fecundity, fertility, larvae death, pupation, adult emergence, adult mosquito longevity were recorded. Adhering to bio-safety, all discarded materials were boiled thoroughly and incinerated if required. This report on the establishment and maintenance of a laboratory colony of Ae. albopictus will be of value for identifying the critical requirements essential under artificial conditions.
Larval indices of vector mosquitoes as predictors of dengue epidemics: An approach to manage dengue outbreaks based on entomological parameters in the districts of Colombo and Kandy, Sri Lanka
(Hindawi Pub. Co., 2020) Udayanga, L.; Aryaprema, S.; Gunathilaka, N.; Iqbal, M. C. M.; Fernando, T.; Abeyewickreme, W.
BACKGROUND: Early detection of dengue epidemics is a vital aspect in control programmes. Predictions based on larval indices of disease vectors are widely used in dengue control, with defined threshold values. However, there is no set threshold in Sri Lanka at the national or regional levels for Aedes larval indices. Therefore, the current study aimed at developing threshold values for vector indices in two dengue high-risk districts in Sri Lanka. METHODS: Monthly vector indices (House Index [HI], Container Index [CI], Breteau Index for Aedes aegypti [BIagp], and Ae. albopictus [BIalb]), of ten selected dengue high-risk Medical Officer of Health (MOH) areas located in Colombo and Kandy districts, were collected from January 2010 to June 2019, along with monthly reported dengue cases. Receiver Operating Characteristic (ROC) curve analysis in SPSS (version 23) was used to assess the discriminative power of the larval indices in identifying dengue epidemics and to develop thresholds for the dengue epidemic management. RESULTS: Only HI and BIagp denoted significant associations with dengue epidemics at lag periods of one and two months. Based on Ae. aegypti, average threshold values were defined for Colombo as Low Risk (2.4 ≤ BIagp < 3.8), Moderate Risk (3.8 ≤ BIagp < 5), High Risk (BIagp ≥ 5), along with BIagp 2.9 ≤ BIagp < 4.2 (Low Risk), 4.2 ≤ BIagp < 5.3 (Moderate Risk), and BIagp ≥ 5.3 (High Risk) for Kandy. Further, 5.5 ≤ HI < 8.9, 8.9 ≤ HI < 11.9, and HI ≥ 11.9 were defined as Low Risk, Moderate Risk, and High Risk average thresholds for HI in Colombo, while 6.9 ≤ HI < 9.1 (Low Risk), 8.9 ≥ HI < 11.8 (Moderate Risk), and HI ≥ 11.8 (High Risk) were defined for Kandy. CONCLUSIONS: The defined threshold values for Ae. aegypti and HI could be recommended as indicators for early detection of dengue epidemics and to drive vector management activities, with the objective of managing dengue epidemics with optimal usage of financial, technical, and human resources in Sri Lanka.
Determination of the efficiency of diets for larval development in mass rearing Aedes aegypti (Diptera: Culicidae)
(CABI Publishing, 2018) Gunathilaka, P.A.D.H.N.; Uduwawala, U.M.H.U.; Udayanga, N.W.B.A.L.; Ranathunge, R.M.T.B.; Amarasinghe, L.D.; Abeyewickreme, W.
Larval diet quality and rearing conditions have a direct and irreversible effect on adult traits. Therefore, the current study was carried out to optimize the larval diet for mass rearing of Aedes aegypti, for Sterile Insect Technique (SIT)-based applications in Sri Lanka. Five batches of 750 first instar larvae (L 1) of Ae. aegypti were exposed to five different concentrations (2-10%) of International Atomic Energy Agency (IAEA) recommended the larval diet. Morphological development parameters of larva, pupa, and adult were detected at 24 h intervals along with selected growth parameters. Each experiment was replicated five times. General Linear Modeling along with Pearson's correlation analysis were used for statistical treatments. Significant differences (P < 0.05) among the larvae treated with different concentrations were found using General Linear Modeling in all the stages namely: total body length and the thoracic length of larvae; cephalothoracic length and width of pupae; thoracic length, thoracic width, abdominal length and the wing length of adults; along with pupation rate and success, sex ratio, adult success, fecundity and hatching rate of Ae. aegypti. The best quality adults can be produced at larval diet concentration of 10%. However, the 8% larval diet concentration was most suitable for adult male survival.

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