Browsing by Author "Ranathunge, R.M.T.B."

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Anopheles subpictus s.l. breeding in polluted water bodies in Vankalai area in the Mannar District
(Sri Lanka Association for the Advancement of Science, 2014) Ranathunge, R.M.T.B.; Gunathilaka, P.A.D.H.N.; Kannangara, D.N.; Abeyewickreme, W.; Hapugoda, M.D.
Climatic factors affecting density of Anopheles vector mosquitoes in Ampara District, Sri Lanka
(University of Kelaniya, 2014) Kannangara, D.N.; Ranathunge, R.M.T.B.; Abeyewickreme, W.; Hapugoda, M.D.; Subasinghe, S.M.C.U.P.
Background: Apart of many vector-borne diseases malaria played a major role during past decades in Sri Lanka. Controlling strategies had effectively addressed this issue so that there were no malaria patients recently. However it has been observed that abundance of vector mosquitoes in districts like Ampara is high, which signifies a potential of spreading of malaria in the area in future. Identification of the relationship between the climatic factors and vector density could be a cost effective way in controlling the mosquito instead of costly strategies currently followed. This study attempts to identify the relationship exists between climatic factors and the vector density in Ampara District.
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.
Diversity of Anopheline mosquitoes (Diptera: Culicidae) in the Trincomalee district during one year
(Sri Lanka Association for the Advancement of Science, 2014) Ranathunge, R.M.T.B.; Gunathilaka, P.A.D.H.N.; Kannangara, D.N.; Abeyewickreme, W.; Hapugoda, M.D.
Effects of socio-economic and socio-cultural risk factors on low malaria transmission in Mannar and Trincomalee Districts of Sri Lanka
(University of Kelaniya, 2014) Gunathilaka, P.A.D.H.N.; Abeyewickreme, W.; Ranathunge, R.M.T.B.; Hapugoda, M.D.; Wickremasinghe, A.R.
The socio-economic and socio-cultural practices of the people differ between communities and play an important role in malaria control operations. The present study was conducted to assess the influence of household socio-economic and socio-cultural status on reduction of malaria transmission in the Districts of Mannar and Trincomalee, which are endemic regions for malaria in Sri Lanka.
Impacts of rubber factory effluents on the macrobenthic community in Gurugoda Oya, Ruwanwella
(Sri Lanka Association for Fisheries and Aquatic Resources, 2012) Ranathunge, R.M.T.B.; Chandrasekera, W.U.
Rubber factory effluents contain a mixture of chemical compounds that bring about harmful impacts to fauna. With this view, the present study was carried out to investigate the changes in water and sediment quality parameters in a freshwater stream, and how the associated macrobenthic community responds upon receiving untreated effluents from a nearby raw rubber processing factory. This study was carried out in the Atala village section of the Gurugoda Oya, a shallow tributary of river Kelani in the Ruwanwella region. Three downstream sampling sites that are 50 m apart from each other from the point of discharge, a pristine control site that is SO m upstream from the point of discharge, and a sampling site within the effluent feeder canal were established for the study. The water flow velocity, temperature, conductivity, pH, DO, BOO" COD, total suspended solids, total dissolved solids, total sulphides, alkalinity and the concentration of Nao, KO, Ca'o, and Mg'O ions in the overlying water and organic matter content in the sediment and the abundance of the associated macrobenthic invertebrate faunas were measured in sufficient replication in each site twice during the dry season and twice during the wet season of the year 2010. The seasonal and site-wise variation of the physico-chemical parameters, abundance of major macrobenthic species and their community structure were analysed. Although the results revealed that the physico-chemical characteristics of water and sediment drastically altered upon receiving the effluents, they regained their ambient levels down in the stream most probably as a result of dilution in the water flow. The macrobenthic faunas in the stream too, responded accordingly where their species richness and diversity significantly (p
Male isolation of dengue vector Aedes mosquitoes for sterile insect technique by spiking blood with ivermectin
(Sri Lanka Association for the Advancement of Science, 2015) Abeyewickreme, W.; Wijegunawardana, N.D.A.D.; Ranathunge, R.M.T.B.
There is an increasing demand for exploration of the potential for applying the Sterile Insect Technique (SIT) in area-wide integrated vector management (AW-IVM) in many countries. However, because female mosquitoes, unlike male mosquitoes, can transmit disease, means to eliminate them from the mass production process are a critical pre-requisite. In addition, the efficiency of the SIT programme could be increased by not releasing female mosquitoes due to the fact that sterile males can then only focus on wild females to achieve mating. Therefore, mosquito SIT programmes success will depend on exclusive release of sterile males, which is impossible on a large scale without efficient sex separation methods. Many different sex separations for different stages of mosquitoes are currently being attempted to successfully establish a sexing mechanism for the above purpose. Among them, the mostly attempted methods broadly include genetic sexing methods, molecular methods, mechanical methods and behavioral methods. For all blood feeding mosquitoes, sex separation could occur at the adult stage by spiking blood with insecticides (malathion, dieldrin) or other mosquito toxins (ivermectin, spinosad), as behavioral tools. In this study, a veterinary preparation of ivermectin (Ivotec,1% w/v) which is used to treat dogs infested with the filarial worm Dirofilaria repens in Sri Lanka was used as a tool for sex separation of adult Aedes albopictus and Aedes aegypti mosquitoes by feeding on spiked blood. In an initial attempt by spiking blood with 5 parts per million (5 ppm) ivermectin, 40% of the blood–fed females could survive beyond 24 hours post feeding. However, when the dosage of ivermectin was increased to 7 ppm the survival rate decreased below 40%. Since there had been high mortality of both females and males even in the control cages in which mosquitoes were blood-fed without ivermectin it was suggested that the age of the mosquitoes used may be a factor for high mortality of mosquitoes in the control experiment. When the experiment was repeated with 7 ppm ivermectin in blood using 4-5 day old mosquitoes more than 65% mortality could be observed within 12 hours post feeding in the experimental cage with a significant difference in mortality compared to the control
Morphological identification and abundance of malaria vectors in the Trincomalee district
(Sri Lanka Association for the Advancement of Science, 2014) Gunathilaka, P.A.D.H.N.; Ranathunge, R.M.T.B.; Hapugoda, M.D.; Wickremasinghe, A.R.; Abeyewickreme, W.
Occurrence of major and potential malaria vector immature stages in different breeding habitats and associated biotic and abiotic characters in the district of Trincomalee Sri Lanka
(New Delhi : National Institute of Malaria Research, 2020) Ranathunge, R.M.T.B.; Kannangara, D.N.; Gunathilaka, P.A.D.H.N.; Abeyewickreme, W.; Hapugoda, M.D.
BACKGROUND & OBJECTIVES: Understanding the effect of biotic and abiotic factors on the biology and ecology of immature stages of anopheline larvae is very important in controlling malaria vector mosquitoes. Therefore, this study was focused on the monitoring of ecological factors affecting the distribution, dynamics, and density of malaria vector mosquitoes in the District of Trincomalee, Sri Lanka. METHODS: Permanent and temporary breeding habitats were identified and selected from five possible malaria sensitive sites in the district of Trincomalee. Anopheles larvae and macro-invertebrates were collected using standard methods for 16 months (from October 2013 to January 2015) and they were identified microscopically. Eight physico-chemical parameters of the breeding habitats were measured. RESULTS: Overall, a total of 4815 anopheline larvae belonging to 13 species were collected from 3,12,764 dips from 18 permanent and temporary breeding habitats. The abundance of anopheline larvae showed a significant positive correlation (p <0.05) with physico-chemical parameters in breeding habitats, such as temperature, dissolved oxygen, and turbidity. A total of 35 macro-invertebrate taxa were collected from the anopheline mosquito breeding habitats. INTERPRETATION & CONCLUSION: This study represents the first systematic update of water quality parameters, macro-invertebrate communities associated with Anopheles mosquito oviposition sites in the District of Trincomalee, Sri Lanka. Rainfall intensity and wind speed are critical meteorological factors for the distribution and abundance of malaria vectors. Knowledge generated on the ecology of Anopheles mosquitoes will help to eliminate malaria vectors in the country. KEYWORDS: Macro-invertebrates; Sri Lanka; malaria vectors; physico-chemical parameters.
Relationship between water quality parameters in rock pools with the Anopheles larvae in the Ampara district
(Sri Lanka Association for the Advancement of Science, 2014) Kannangara, D.N.; Gunathilaka, P.A.D.H.N.; Ranathunge, R.M.T.B.; Abeyewickreme, W.; Hapugoda, M.D.
Species succession of malaria vector mosquitoes and physicochemical factors affecting their abundance in rice ecosystems in Trincomalee, Sri Lanka
(University of Kelaniya, 2013) Gunathilaka, P.A.D.H.N.; Ranathunge, R.M.T.B.; Fernando, M.A.S.T.; Hapugoda, M.D.; Wijeyerathne, P.; Wickremasinghe, A.R.; Abeyewickreme, W.
Background: Mosquito-borne diseases are a major public health threat in Asia. The present investigation was carried out to study the ecology of vector mosquitoes in Sri Lanka, in order to explore effective mosquito control strategies in rice ecosystems from the ecological point of view. Method: As part of investigations on potential linkages between irrigation and malaria transmission, all surface water bodies in and around 20 selected villages along an irrigation distributary in the District of Trincomalee, Sri Lanka, were surveyed for anopheline mosquito larvae (Diptera: Culicidae) from January 2012 - June 2013. Breeding sites were characterized according to exposure to sunlight, substratum, and presence of vegetation, fauna, inorganic matter and physical water condition (clear/turbid). Dissolved Oxygen (DO), conductivity, salinity, pH, temperature, Total Dissolved Solids (TDS) and turbidity were recorded. Results: A total of 3914 Anopheles larvae of twelve morphological types were collected from 685 breeding habitats. Anopheles peditaeniatus (n= 1041), was the most abundant, followed by An. subpictus (n= 893), An. nigerrimus (n= 808), An. barbirostris (n= 581), An. pallidus (n= 184), An. annularis (n=124), An. jamesii (n= 80), An. varuna (n= 76), An. vagus (n= 56), An. barbumbrosus (n= 48). An. culicifacies (n= 22) and An. aconitus (n= 1). The four most abundant species were significantly associated with waterlogged paddy fields. Anopheles culicifacies was noted only from irrigational canals with vegetation. Conductivity, salinity, and TDS were positively correlated with larval densities of An. peditaeniatus (Pearson correlations= 0.04, 0.17, 0.33: P= 0.94, 0.77, 0.58), An. subpictus (Pearson correlations= 0.6, 0.68, 0.56: P= 0.19, 0.20, 0.31), and An. vagus (Pearson correlations= 0.6, 0.42, 0.17: P= 0.28, 0.47, 0.77). However all physicochemical variables were negatively correlated with An. culicifacies densities. Conclusion: Major malaria vector of An. culicifacies complex occurred at relatively low densities, mainly in irrigated and waterlogged fields. These findings support understanding of mosquito ecology and will support future mosquito control strategies in rice ecosystems in Sri Lanka.