ARS - 2013
Permanent URI for this collectionhttp://repository.kln.ac.lk/handle/123456789/171
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Item Detection of pathogenic Leptospira species in rat blood samples by molecular-based assays(University of Kelaniya, 2013) Denipitiya, D.T.H.; Chandrasekharan, N.V.; Abeyewickreme, W.; Hapugoda, M.D.Background: Leptospirosis is a worldwide zoonotic infection, caused by pathogenic species of the genus Leptospira. It was traditionally known as ‘rat fever’ in Sri Lanka, because rodents, especially rats, are considered to be the most important reservoirs or maintenance hosts of Leptospira. In 2012, the highest numbers of cases were reported in the District of Gampaha. The objective of this study is to detect pathogenic Leptospira species in rat blood samples by molecular based assays. Method: Rats (n=38) were trapped in a high risk area (Mirigama) in the District of Gampaha, from May 2012 to February 2013 by using live traps. Each rat was anesthetized by using diethyl ether and 2-3 ml sample of blood was collected from each rat. Blood samples collected from all rats were tested by molecular- based assays and a serological assay. Qualitative Polymerase Chain Reaction (PCR), real time PCR and Loop Mediated Isothermal Amplification (LAMP) were used as molecular-based assays which targetted conserved gene regions among pathogenic serovars of Leptospira species. Microscopic Agglutination Test (MAT), the Gold Standard assay for detection of anti Leptospira antibody was used as a serological assay. Results and Discussion: Of the 38 rat blood samples, molecular-based assays confirmed Leptospira infection in 5% (2/38), 16% (6/38) and 11% (4/38) by qualitative PCR, real time PCR and LAMP assay respectively. None of the samples was positive by MAT. After first infection, some Leptospira species live in the host animal as commensal bacteria. Therefore, host does not stimulate antibody production further and that may be below the detection level of the antibody by MAT. Conclusions: Results of molecular based assays showed that Leptospira are circulating among the rats tested in this study, although at the time of collection, their antibody levels were too low to detect by MAT, which had the lowest detection limit of 1:800.Item Risk factors associated with human leptospirosis in the District of Gampaha, Sri Lanka(University of Kelaniya, 2013) Denipitiya, D.T.H.; Athapaththu, M.; Chandrasekharan, N.V.; Abeyewickreme, W.; Hapugoda, M.D.Background & Objective: A large number of leptospirosis cases are recorded in Sri Lanka every year. Increased numbers of cases have been reported in the District of Gampaha in the recent past. The incidence of leptospirosis is often influenced by various socio-economic, occupational, environmental and other factors. To date, a study on potential risk factors has not been conducted in the District of Gampaha. The objective of this study is to identify risk factors involved in transmission of leptospirosis to humans in the District of Gampaha. Methods: Data were collected at the household level, using an interviewer-administered questionnaire and by inspecting the surrounding of laboratory confirmed leptospirosis patients (n=81) and non leptospirosis persons (n=117) during the period of June 2011 to June 2013. The risk factors in the questionnaire were divided into three broad categories: environmental, contact with animals and behavioral/occupational factors. Chi-square test (The SAS System for Windows 9.0) was used for comparison of data from different categories. Results and discussion: 95% of the leptospirosis patients were adult males (77/81) and they had a monthly income of Rs. 10,001-20,000 and 50% of them were agricultural and rental work labourers (40/81). In contrast, 56% of persons not infected with leptospirosis were adult females (66/117) and most of them (48%) were housewives or homemakers (56/117). Data on the type of premises were collected under three categories as poor, moderate and well constructed along with the land use type of the surrounding areas. There were significant statistical associations between the leptospirosis patient with the type of premises (, χ2=23.38, p=0.00), surrounding cleanliness of premises (χ2=45.05, p=0.00), sanitary facilities (χ2=11.66, p=0.00), waste disposal method (χ2=32.23, p=0.00) and age level of patients (χ2=21.07, p=0.00). No significant statistical associations were observed between recorded leptospirosis cases and vegetation coverage in surrounding area of premises (χ2=1.25, p>0.05), source of drinking water (χ2= 0.55, p>0.05) and numbers of persons in family (χ2=0.17, p>0.05). Conclusion: Identification of the potential risk factors would help understand the transmission dynamics of the disease and formulate public health interventions.Item 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.Item Resting behavior of malaria vectors in Mannar District of Sri Lanka with reference to zooprophylaxis(University of Kelaniya, 2013) Gunathilaka, P.A.D.H.N.; Fernando, M.A.S.T.; Hapugoda, M.D.; Wijeyerathne, P.; Wickremasinghe, A.R.; Abeyewickreme, W.Background: The most important factors for effective zooprophylaxis in reducing malaria transmission are the presence of predominate populations of a strongly zoophilic mosquitoes and domestic animals for their blood-meal. Methods: Resting behavior of anopheline mosquitoes was evaluated using indoor and outdoor mosquito collection techniques. Mosquitoes were captured using 389 outdoor cattle-baited traps and indoor hand catches in 5672 houses at 12 possible malaria sensitive areas situated 12 km apart; Pesali, Keeri, Erukkallampeddi, Moor, Vankalai, Narawallikulam, Vanchiyankulam, Arvanum, Arrippu, Kokkupadayan, Koolankulam and Pandaraveilli for 12 months (June 2012 to June 2013) on a weekly basis. These areas had mostly homogenous characteristics in vegetations and house type. All collected mosquitoes were identified using standard taxonomic keys. A hypothesis test was conducted to determine whether there is a difference between indoor and outdoor collections. Results: A total of 3986 anopheline mosquitoes were collected from both indoor (n= 3122) and outdoor (n= 864) collection techniques. Anopheles subpictus was found to account for over 97.5% (n= 3887) of Anopheles species collected in the study areas. Other species were; 1.4% An. peditaeniatus (n= 57), 0.6% An. varuna (n= 22), 0.3% An. pallidus (n= 10), 0.2% An. nigerrimus (n= 7), 0.05% An. tessellatus (n= 2), and 0.03% An. aconitus (n= 1). Only 3 species namely, An. subpictus (n= 485), An. tessellatus (n= 2) and An. aconitus (n= 1) were recorded from indoor hand catches. In experimental cattle-baited hut trials, An. subpictus (n= 3026) was found to have the highest exophilic tendency (96.9%) compared to other anophelines encountered. The hypothesis test suggests that there was a significant difference of An. subpictus attracted to cattle-baited traps and human dwellings (P = 0.008). Although the main vector An. culicifacies was absent, the presence of the secondary vector An. subpictus was observed in high numbers in the District. Conclusion: Exophilic and zoophilic tendencies of An. subpictus are conducive for zooprophylaxis. The study further indicates that zooprophylaxis may be a potential strategy for malaria control. It is recommended that in areas with a predominant An. subpictus population, cattle could be kept close to human dwellings to maximize the effects of zooprophylaxis.