IPRC - 2016
Permanent URI for this collectionhttp://repository.kln.ac.lk/handle/123456789/157
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Item Characterization of a Dengue Positive Population in Colombo Municipal Council (CMC) Medical Officer of Health (MOH), Colombo(Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2016) Lakmal, M.G.K.; Udayanga, N.W.B.A.L.; Gunathilaka, P.A.D.H.N.; Fernando, S.D.; Karunathilaka, K.; Abeyewickreme, W.Dengue that has caused 29,777 suspected infections in 2015 has emerged the most challenging health issue faced in Sri Lanka. Approximately 51% of dengue infections are reported from the Western Province. The susceptibility of a population to dengue is influenced by a combination of socio-economic, environmental and epidemiological factors. The current study was conducted to characterize a population of dengue patients residing in a high dengue risk area in terms of their socio-economic appearance. An interviewer administrated questionnaire was used to collect information on the socio-economic aspects of a group of 140 randomly selected dengue positive patients residing in Colombo Municipal Council (CMC) Medical Officer of Health (MOH) area. Out of 140, a majority (63.6%, n=89) were females, while the age groups of 31-40 and 21-30 years were recognized as the most susceptible age groups for dengue. High proportion of the patients (79.3%, n=111) were having an educational level below secondary school (O/L) with a total family income below 20,000 LKR (80.7%, n=113). All the homesteads were smaller (<5 perch) in size, with small roads for access (77.1%, n=108) and/or a footpath (22.9%, n=32) as the access route. Majority of the households (69.3%, n=97) were temporary with moderate conditions (51.4%, n=72), that were mainly utilized for both residential and commercial purposes (63.5%, n=89) at once. In a majority of households’ solid waste was disposed within 7 days (62.1%) via the Municipal Council or by keeping near the main roads (37.9%). Source separation of waste, home gardening and composting by the study population was minimal (n=137, 97.9%). Pipe water remained as the only water source while approximately 27.9% (n=39) households were lacking sanitary facilities. Use of mosquito coils and bed-nets were the most preferred mosquito biting prevention methods. Low educational level, income, poor living conditions and limitations in solid waste disposal methods were recognized as potential risk factors for high infection rates of dengue in this population. Special focus should be given to these key areas by the relevant vector controlling authorities in order to facilitate controlling of dengue outbreaks within the CMC area.Item Eliminating female Aedes mosquitoes by spiking blood meals with toxicants as a sex separation method in the context of the sterile insect technique and Incompatible Insect Technique(Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2016) Ranathunga, R.M.T.B.; Gunathilaka, P.A.D.H.N.; Udayanga, N.W.B.A.L.; Wijegunawardena, N.D.A.; Abeyewickreme, W.Ivermectin and spinosad have longevity reducing effects in several insect species, including disease transmitting mosquitoes after feeding blood contaminated with above toxicants on hosts. Therefore, this approach could play an enormous role in mosquito control operations by its use in the female elimination process during mass-rearing, enabling the release of only sterile males in the context of the sterile insect technique (SIT) and incompatible insect technique (IIT) with Wolbachia bacterium. Blood meals of cattle origin were spiked with diffeerenct concentrations (2, 4, 6, 8 and 10 ppm) of Ivermectin (Ivotec, 1% w/v) and Spinosad (Spinosyn, 12% w/v) and offered to a batch of adult Ae. aegypti (n = 300) and Ae. albopictus (n = 300) having 1:1 sex ratio in order to obtain an optimal dose for quick and total female elimination. After 24 hours all remaining females and males were aspirated out and transferred in to new cages separately. An additional blood meal with the initially fed concentrations of ivermectin and spinosad was provided after 24 hours, followed by a 48-hour observation of mortality. This experiment was repeated by feeding cattle blood containing a mixture of ivermectin and spinosad in 1:1 ratio from each concentration. Spiked blood with 8 ppm ivermectin and spinosad killed all the fed females of Ae aegypti and Ae. abopictus within 24 to 48 hours. It was observed that the number of fed females gradually increased, when decreasing the toxicity in combination of ivermectin and spinosad (1:1) in blood for both species. Male mortality did not show any significant differences during the study. Mixed feeding of blood with 8 ppm ivermectin and 8 ppm spinosad have shown as the viable treatment to eliminate female Ae aegypti and Ae. abopictus from laboratory colonies.Item Prevalence of dengue vector breeding habitats among selected Schools in Gampaha District of Sri Lanka(Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2016) Radhika, N.M.L.; Gunathilaka, P.A.D.H.N.; Kasturiratne, K.T.A.A.; Abeyewickreme, W.Aedes aegypti and Aedes albopictus are the vectors responsible for the transmission of dengue viruses in Sri Lanka. Gampaha District has been ranked as the second most Dengue affected area. Recently, health authorities have identified that over 54 percent of schools have dengue mosquito breeding sites. However, the entomological information on the dengue vectors in School premises are not available. Therefore, the present study was carried out to identify the different breeding sites of dengue vector mosquitoes within school premises of randomly selected schools in Gampaha District of Sri Lanka. The premises of the selected schools (n= 34) were surveyed from May to October in 2016 for the availability of potential breeding habitats and the presence of vector breeding through entomological surveys. Collected vectors were identified morphologically and categorized inn to species level. All data on breeding habitats and number of vectors identified were recorded. According to survey, out of 34 schools surveyed; infested water-holding containers by Ae. albopictus were observed at 16 schools (47, 05%). Tree holes (Bridelia retusa tree), leaf axils of banana tree and fallen leaves were observed as natural breeding sites while, discarded plastic food containers plastic paint containers, broken pet bottles, tire marks on the ground, water retaining flower pots and plastic barrels were observed as artificial breeding sites. Breeding of Ae. aegypti was not identified among the school premises surveyed. Improper management of solid waste has affected positively in creating suitable habitats for vector breeding. Therefore, continuous monitoring of dengue vector breeding habitats and school based vector controlling interventions should be implemented through proper awareness and active participation for eliminating breeding habitats.Item Assessment of artificial blood feeding methods and efficacy of different blood meal sources in mass rearing of Aedes aegypti for innovative vector controlling strategies(Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2016) Gunathilaka, P.A.D.H.N.; Ranathunga, R.M.T.B.; Udayanga, N.W.B.A.L.; Abeyewickreme, W.Background Mass rearing of vector mosquitoes of dengue is a crucial requirement for implementation of innovative vector controlling strategies such as Sterile Insect Technique (SIT), Incompatible Insect Technique (IIT) and transgenic mosquitoes. Selection of the artificial membrane-feeding technique and blood meal source have been recognized as key considerations in mass rearing of vectors. Methodology Three artificial membrane feeding techniques (Glass plate method, Metal plate and Hemotek membrane feeding method) and three blood sources (human, cattle and chicken) were evaluated based on feeding rates, fecundity and hatching rates of Ae. aegypti, under laboratory conditions. One-way ANOVA, cluster analysis, analysis of variance (ANOSIM) and principal coordinates (PCO) analysis, were used to investigate the significance in the variations among blood feeding. Results Feeding rates of Ae. aegypti significantly differed among the membrane feeding techniques as suggested by one-way ANOVA (p <0.05). The metal plate method was identified as the most efficient and cost effective feeding technique. Blood feeding rate of Ae. aegypti was higher with human blood followed by cattle and chicken blood, respectively. However, no significant difference was observed among mosquitoes fed with cattle blood and human blood, in terms of fecundity, oviposition rate and fertility. Conclusions Metal plate feeding technique could be recommended as the most effective membrane feeding technique for mass rearing of Ae. aegypti, due to its high feeding rate and cost effectiveness. Since, obtaining human blood for insectary colony maintenance is problematic due certain ethical issues, cattle blood could be recommended for mass rearing Ae. aegypti.Item Evaluation the Oviposition Behaviour of Aedes Aegypti and Ae. Albopictus Mosquitoes; Main and Secondary Vector for Dengue Transmission in Sri Lanka under Laboratory Conditions(Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2016) Gunathilaka, P.A.D.H.N.; Ranathunga, R.M.T.B.; Udayanga, N.W.B.A.L.; Abeyewickreme, W.Studies on the oviposition behavior of Aedes albopictus and Ae. aegypti are critical for effective controlling of dengue vector breeding. However, less attention has been drawn on such aspects of vector biology and bionomics in Sri Lanka. Therefore, the objective of the current study was to evaluate the oviposition behavior of dengue vectors under laboratory conditions. Ovitraps with different sizes, colours, sources of water, sodium chloride (NaCl) concentration (0.2, 0.5, 1, 2 and 3%) and presence and absence of larvae were kept within separate cages of batches of 1000 Ae. albopictus and Ae. aegypti with (1:1, male: female ratio). Female mosquitoes were allowed to lay eggs and the number of eggs laid in different ovitraps were enumerated. ANOVA and cluster analysis were used to investigate the significance in the variations among oviposition behaviours. The mean number of eggs laid by both Ae. albopictus and Ae. aegypti increased with the increasing size of the ovitraps. Ae. albopictus indicated the highest mean number of eggs in 0.2% of NaCl than that of distilled water, while the egg laying preference reduced with the increasing salinity for both species. Drain water with low dissolved oxygen level (0.43 ± 0.12 mg/l) was the preferred water source for both species and indicated a significantly high oviposition rate in ovitraps with larvae. Black colour ovitraps attracted the majority of the gravid females, while white was least preferred. There were no significant variations among oviposition behaviors of Ae. albopictus and Ae. aegypti under laboratory conditions. Back coloured ovitraps were the preferred breeding place.Item A preliminary community survey of selected dengue patient households in the Ragama MOH, Gampaha District(Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2016) Wijegunawardana, N.D.A.D.; Gunathilaka, N.; Udayanga, L.; Gunawardene, N.; Dassanayake, R.; Chandrasena, N.; Bourtzis, K.K.; Abeyewickreme, W.Socio-economic aspects of the local population has been found to directly influence the emergence of dengue epidemics. Thus, a preliminary community survey was conducted among 30 randomly selected dengue positive patient households in the Ragama Medical Officer of Health (MOH) area, in Gampaha District to assess the socio-economic and demographic level of the patients. Study premises were selected randomly based on the MOH records during the year of 2015 and the selection of the premises was purposely limited to Narangodapaluwa Public Health Inspector area that has reported the highest number of dengue cases. An interviewer administrated questionnaire was used for the collection of socio-economic and demographic aspects of the patient households. Among the selected households; 40% (n=12) had at least more than 2 dengue positive patients among the occupants, while 42 dengue positive patients were interviewed in total. Age distribution of positive patients ranged from 1 - 70 years, while mean and mode represented 35 and 19 years, respectively. Relative distribution of male to female ratio remained as 1:1. Around 50% of the patients had an educational level higher than intermediate school education (O/L). Based on the indirect questions regarding the possible factors affecting the DF transmissions, it was noted that only participants 26 out of 42 (61.90%), have been infected with DF more than once in their life time regardless of living in the same study area since birth. Twenty-two patients (52.38%) claimed that they believe, that the DF infection has acquired at home. Meanwhile others claimed (n=20, 47.68%) that possible DF infection acquired site could be outside environments, probably schools or the place of work. Cleanliness of the surroundings was maintained well at almost all households, while waste disposal was properly maintained at weekly intervals by urban council in 14 premises. Others practiced open ground burning twice a week. Most of the respondents were willing to support Aedes control measures and follow mosquito bite prevention methods (n=28, 93.33%). Majority of the households (n=21) were not satisfied with the government vector controlling activates within the area. There is no significant association between socio demographic and economic data with DF transmission within the study population. Relative abundance of Aedes mosquito population in existing rubber plantation could be a reason for the occurrence of high rate of DF cases. Thus, practice of effective integrated vector control measures within the study area is highly recommended for the controlling of dengue.