Browsing by Author "Gunathilaka, N."

Now showing 1 - 20 of 78

Abundance and taxonomic characterization of chigger mites (Acari: Trombiculidae and Walchiidae) associated with rodents in selected scrub typhus-prone areas in Southern and Western provinces of Sri Lanka
(University of Kelaniya, 2024) Liyanage, A.; Gunathilaka, N.; Premarathne, R.; Chandrasena, N.; Jacinavicius, F.D.C.; Silva, R.B.
Larval trombiculid mites (chiggers) are the vectors and reservoirs of the potentially lethal infectious disease, scrub typhus (ST) caused by Orientia tsutsugamushi. Small rodents are natural hosts of parasitic larval stage of the chigger mites. This study focused on determining the abundance of chigger mites associated with rodents in Sri Lanka and the taxonomic characterization of field-caught chiggers. Field sampling was conducted in the districts of Galle, and Hambantota of the Southern Province, and Gampaha of the Western Province, in 2019 and 2020. Sampling sites were selected according to the patient distribution. Rodents were captured using baited traps (7.62 cm x 7.62 cm x 25.4 cm) set up just before sunset at peri-domestic or work premises of ST fever patients. A total of 422 traps were placed at identified possible exposure locations in Galle (n=122), Hambantota (n=120) and Gampaha (n=178). A total of 58 small mammals were captured [Galle (n=19), Hambantota (n=7), and Gampaha (n=32)] under three small rodent species, namely; Rattus rattus (Black rat), Rattus norvegicus (Brown rat), Tatera indica (Indian gerbil), Gollunda ellioti (Indian bush rat) and Suncus murinus (Asian house shrew). The trapped rodents were anaesthetized with ketamine (75 mg/kg) /xylazine (10 mg/kg) and examined for larval mites. Mites detected were removed carefully with a brush, collected, and washed individually with 10% PBS and slidemounted in Hoyer’s medium. Chiggers were speciated morphologically by visual inspection and morphometry using a camera-mounted light microscope (x100). A total of 394 life stages of mites were collected. Three different genera were identified, including Leptotrombidium, Schoengastiella, and Microtrombicula. Leptotrombidium imphalum (72.59%; n=286) was the predominant species, followed by Schoengastiella punctata (8.12%; n=32). Some specimens were identifiable only up to genus level, Leptotrombidium sp. (3.55%; n=14) and Microtrombicula sp. (4.82%; n= 19). Some (7.11%; n=28) were not trombiculid mites, while 3.81%; n=15 was damaged beyond identification. Leptotrombidium imphalum was detected for the first time parasitizing the murids - Rattus novergicus and Tatera indica in the district of Galle, a new locality. In addition, S. punctata was recorded in a new locality in the Gampaha district, Western province with a new host association, Golunda ellioti. This study emphasizes the need for further entomological surveys in ST disease-endemic areas. Developing a morphological identification key for chigger mites in Sri Lanka is a top priority to facilitate field surveys.
Anopheles culicifacies breeding in polluted water bodies in Trincomalee district of Sri Lanka
(BioMed Central, 2013) Gunathilaka, N.; Fernando, T.; Hapugoda, M.; Wickremasinghe, R.; Wijeyerathne, P.; Abeyewickreme, W.
BACKGROUND: Anopheles culicifacies, the major vector of malaria in Sri Lanka, is known to breed in clean and clear water. The main objective of the study was to detect the breeding habitat diversity of An. culicifacies. METHODS:Potential larval habitats for Anopheles mosquitoes were surveyed on a monthly basis for 17 months (January 2011--June 2012) in four different selected sampling sites (Murthankulam, Kommnaimottai, Paranamadawachchiya and Kokmotawewa) in Trincomalee District of Sri Lanka. RESULTS: A total of 2,996 larval specimens representing 13 Anopheles species were reported from 16 different breeding habitats. According to density criterion, An. culicifacies, Anopheles subpictus, Anopheles barbirostris, Anopheles peditaeniatus and Anopheles nigerrimus were dominant. Anopheles nigerrimus, An. subpictus and An. peditaeniatus were observed as constant in relation to their distribution. The most productive breeding site for An. culicifacies was drains filled with waste water in remote areas; the second highest productivity was found in built wells. CONCLUSIONS: These results indicate that An. culicifacies has adapted to breed in a wide range of water bodies including waste water collections although they were earlier considered to breed only in clean and clear water. Copyright © 2013 Gunathilaka et al.; licensee BioMed Central Ltd.
Appearance of Anopheles jeyporiensis James from Sri Lanka; a new species to the mosquito checklist
(The Japan Society of Medical Entomology and Zoology, 2015) Gunathilaka, N.; Abeyewickreme, W.; Hapugoda, M.; Wickremasinghe, A.R.
Previous records of Sri Lankan Anopheles were most imperfect, and even the number and names of the species present were very doubtful. There was no systematic study conducted for Sri Lankan adult anophelines since 1990. Therefore, the objective of this study was to explore the species abundance and morphological variations of anopheline mosquitoes in Sri Lanka. Entomological surveys were conducted on a monthly basis from June 2010 to December 2013 in Trincomalee District, using five entomological techniques. Entomological surveys identified a total of 131,804 mosquito specimens belong to 18 anopheline species. One of which was An. jeyporiensis, a species that was not in the checklist in Sri Lanka. Its basic morphological features are similar to the members in Myzomyia series under the subgenus Cellia. Following characteristics were used to confirm the species as An. jeyporiensis; Centre of the scutum covered with short oblong white scales extending back to scutellum; Vein R 1 usually with accessory pale spot on preapical dark (PD) area; Foretarsomere 1 with apical pale band nearly 2.0 width of tarsomere diameter.
Assessment of anxiety, depression, stress, and associated psychological morbidities among patients receiving ayurvedic treatment for different health Issues: first study from Sri Lanka.
(Hindawi Pub. Co., 2019) Gunathilaka, H.J.; Vitharana, P.; Udayanga, L.; Gunathilaka, N.
BACKGROUND:Good mental condition is a vital part of health. Physical impairments would potentially have psychiatric manifestations during the course of a disease that could cause patients to experience a wide range of psychological conditions. This study was conducted to determine prevalence of anxiety, depression, stress, and psychological morbidities among the patients who received warded treatments at Gampaha Wickramarachchi Ayurveda Teaching Hospital, Sri Lanka. METHODS: A total of 148 patients admitted to the hospital were selected for the study on a random systematic basis under four systemic groups (gastrointestinal, integumentary, musculoskeletal, and nervous system) depending on the chief complaint. The presence of depressive, anxiety, and stress symptoms was assessed by the Depression Anxiety Stress Scale 21 item version (DASS 21). The General Linear Model (GLM) was used for statistical analysis. RESULTS:Over 50% of the participants in all four patient groups belonged to age group of 35 to 65 years, encompassing the fraction of population that actively contribute to the workforce in the society. Stress, anxiety, and depression values of patients belonging to different complications varied significantly, as indicated by GLM (p < 0.05). Patients diagnosed with integumentary system-related issues denoted the highest stress levels (27.7 ± 2.54), while the mean stress values among the other systemic groups were not significantly different among each other. The highest anxiety levels were indicated by patients with nervous system-related issues (18.6 ± 1.51), while the lowest anxiety levels were indicated by patients with integumentary disorders (6.0 ± 2.73). The highest depression level was identified from patients suffering from integumentary system-related disorders (31.7 ± 3.42), followed by nervous system (23.2 ± 1.78), gastrointestinal (19.5 ± 3.77), and musculoskeletal (16.8 ± 1.57) disorders. CONCLUSION:Overall, high distress levels were observed among the majority of the patients. Furthermore, integumentary issues may lead to significant psychological impacts. As most of the patients seek for Ayurveda treatments when their diseased condition becomes chronic, it is vital to focus on a biopsychosocial approach to patient assessment and patient care, in actual practice.
Assessment of knowledge and attitude towards the palliative care among nurses in Sri Lanka: A hospital- based study.
(Sage Publishing, 2023) Wijesinghe, T.; Gunathilaka, N.; Mendis, S.; Udayanga, L.
OBJECTIVE: Palliative care is an intervention that improves the quality of life of patients. Nurses have a primary role in providing palliative care. Their knowledge and attitudes toward palliative care is important in care delivery. There is minimal information in Sri Lanka to document the knowledge and attitude of palliative care among nurses. Therefore, the present study was conducted to assess the knowledge and attitude of palliative care among nurses in Sri Lanka. METHOD: A cross-sectional, descriptive study was conducted on 200 selected nurses at Colombo North Teaching Hospital, Sri Lanka fulfilling the inclusion criteria. Socio-demographic information of the study participants was obtained through a self-administered questionnaire. The awareness and attitude levels toward the PC were assessed using the Palliative Care Knowledge Test (PCKT) and Frommelt Attitude Toward Care of the Dying, respectively. RESULTS: More than half of the participants (55%) had an inadequate knowledge level regarding the palliative care (<50% for the PCKT score). Regarding the attitude on the palliative care, the majority stated nursing care to a dying person is a worthwhile experience (92%; n = 184). Many of them disagreed with avoiding the care of dying patients (strongly disagree: 37%; n = 74, disagree: 52.5%; n = 105). Overall, 85.5% of study participants had a positive attitude towards the palliative care. According to binary logistic regression, gender (P = .04; OR = 3.57; CI = 1.03-12.41) and working setup (P < .001) were significantly associated with having a positive attitude. The knowledge level was higher among nurses working in surgical wards (OR = 7.84). Those with >10 years of experience were statistically significant to have a positive attitude (P = .02; OR = 1.35; CI = 1.13-5.50). CONCLUSION: The nurses had inadequate knowledge of the PC even though they had a positive attitude toward it. Therefore, it is essential to uplift the awareness level among health workers. This warrants the need for palliative care education in the nursing curriculum and continuous professional development.
An automated machine learning approach to detect Leishmania parasites: An alternative tool for Leishmaniasis disease diagnosis
(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Amarathunge, J. A.Y.S.; Gunathilaka, N.; Sudusinghe, H.; Nilaweera, T. H. W. T.
Leishmaniasis is a neglected tropical disease caused by a protozoan parasite that poses a significant threat to human life on a global scale. Leishmaniasis is endemic in 99 countries with more than 12 million people infected. Despite being the primary diagnostic method, microscopy needs technical expertise. Since there is no systematized surveillance programme for Leishmaniasis in Sri Lanka, trained personnel to be involved in disease diagnosis by microscopy is limited and only a few health care institutions have such trained individuals. Therefore, this study aimed to study the feasibility of using an automated machine learning programme to detect Leishmania parasites in the microscopic fields. A machine learning model is built on the TensorFlow framework and employs a combination of Convolutional Neural Networks for feature extraction and classification. A total of 150 views of 75 microscopically positive slides for Leishmania parasites (amastigotes) were photographed. Slides that were negative for the parasites were also captured in similar numbers. All captures were fed into the model and tested with 25 positive and negative fields. The machine learning model developed in this study detected 94.1% (n=34) negative fields as negative for Leishmania parasites. Of the positive fields, 93.3% (n=32) of them were detected as positive for the parasites by the developed model. The model indicated 92% accuracy for the detection of Leishmania parasites in the microscopic fields. This level of accuracy can significantly enhance early detection and prompt treatment, potentially reducing the disease burden, complications, and healthcare costs in regions where resources are limited. The model’s versatility permits this approach to be adapted for the detection of other parasitic diseases in Sri Lanka which are not common at present. The proposed method would be a better alternative to disease diagnosis in low-resource settings with limited technical expertise. However, it is recommended to validate the model with more sample data to obtain a better accuracy and applicability.
Biology, bionomics and life-table studies of Anopheles stephensi (Diptera: Culicidae) in Sri Lanka and estimating the vectorial potential using mathematical approximations
(Elsevier, 2023) Jude, J.; Gunathilaka, N.; Udayanaga, L.; Fernando, D.; Premarathne, P.; Wickremasinghe, R.; Abeyewickreme, W.
Background: Anopheles stephensi is an invasive mosquito in Sri Lanka that can potentially transmit malaria. The transmission intensity is linked with biology, bionomic and behavioral aspects of a vector that are associated with the Vectorial Capacity (VC). However, the influence of larval conditions eventually affects the vectorial potential of An. stephensi are not well understood. Methods: A colony of An. stephensi was established at the Regional Centre of the Open University of Sri Lanka, Jaffna District. The colony was maintained under confined conditions according to standard protocols. Biotypes of An. stephensi were characterized by referring to the number of egg ridges. Information on (a) biological aspects of eggs (duration for egg hatching, egg development and hatchability), (b) larval development time, larval survivorship pupation success, resting depth of larvae), (c) pupae (adult emergence rate, average time for adult emergence) and (d) adults (biting frequency, mating success gonotrophic cycle, fecundity, duration for egg-laying, percentage of sexes, adult survival/longevity) were evaluated under life-table analysis. Further, selected morphometric characters of each life cycle stage were recorded from the eggs (length and breadth), larvae (head length, width of head, length of thorax, width of thorax, length of abdomen, width of abdomen, and the total length of larvae), pupae (cephalothoracic length and width) and adults (length & width of wing, thorax and abdomen). The VC was calculated using a mathematical-based approach. Descriptive statistics, General Linear Model (GLM) and independent-sample t-test were used for the statistical analysis. Results: All three biotypes were identified based on egg morphology. Mysorensis biotype (47%; n = 470) was predominant followed by type (38.1%; n = 381) and intermediate (14.9%; n = 149). The mean egg length (F(2,997) = 3.56; P = 0.029) and breadth (F(2,997) = 4.57; P = 0.011) denoted significant differences among the three biotypes. The mating success of females observed was 80.7 ± 4.45%. The mean hatching period was 1.9 ± 0.03 days, with a hatching rate of 86.2 ± 0.77%. Overall, 8.0 ± 0.14 days were required for larval development and 30.3 ± 0.14 h were spent in the pupal stage. The pupation success was 94.5 ± 0.37%, and the majority were males (53.1 ± 0.73%). The mean fecundity was 106.5 ± 6.38 eggs and a gonotrophic cycle of 3.4 ± 0.06 days. The female survival rate was 43.2 ± 2.4%, with a mean biting frequency of 66.6 ± 3.5%. The average VC of adult An. stephensi was estimated to be 18.7. Conclusions: The type biotype, which is an effective vector in the Indian subcontinent is present in Sri Lanka. According to the mathematical approximation, An. stephensi found locally has a vectorial capacity of over 18. Therefore, this study warrants the health authorities and vector control programmes to continue the entomological surveys, monitoring of vector densities and implementing appropriate vector control interventions based on biology and bionomic information of vectors.
Bionomic aspects of dengue vectors Aedes aegypti and Aedes albopictus at domestic settings in urban, suburban and rural areas in Gampaha District, Western Province of Sri Lanka
(BioMed Central, London, 2022) Dalpadado, R.; Amarasinghe, D.; Gunathilaka, N.; Ariyarathna, N.
Background: The lack of information on behavioural patterns of Aedes aegypti and Aedes albopictus has become a significant limitation in vector control and disease management programmes. Therefore, the current study was focused on determining some bionomics aspects: breeding, resting, host-seeking and feeding preferences of Ae. aegypti and Ae. albopictus in Sri Lanka. Methods: Larval and adult surveys were conducted from April 2017 to April 2019 monthly in six selected Medical Officer of Health (MOH) areas in Gampaha Distinct, Western province, Sri Lanka, representing urban, suburban and rural settings. Resting preferences of adult mosquitoes were observed from indoor and outdoor places using a Prockopack aspirator. The information on resting height, surface, material and locality was recorded. Human-baited double-net traps were used to determine the host-seeking time of Aedes mosquitoes. Statistical differences in the spatial distribution of mosquitoes in selected MOH areas and prevalence of vectors were analysed using general linear model (GLM). A chi-square test was used to analyse the resting behaviour. Results: Total of 19,835 potential breeding sites were examined at 13,563 premises, and 18.5% (n = 1856) were positive for Aedes larvae. Distribution of Ae. aegypti and Ae. albopictus was statistically significant at species level (df = 1; F = 137.134; P < 0.05 GLM) and study setting (df = 2; F = 8.125; P < 0.05). Aedes aegypti breeding was found mainly in temporary removals (18.8%; n = 34), discarded non-degradables (12.15%; n = 22) and tyres (9.95%; n = 18). Natural (14.7%; n = 246) and temporary removals (13.6%; n = 227) and discarded non-reusable items were the key ovipositing sites for Ae. albopictus. In the adult mosquito survey, the majority was comprised of Ae. albopictus (54.5%; n = 999), which denoted exophilic nature (90.8%; n = 758), and 45.5% (n = 835) represented by Ae. aegypti mosquitoes who were mainly endophilic (84.3%; n = 842). Aedes aegypti rested on cloth hangings and curtains, followed by the furniture, while Aedes albopictus was predominant in outdoor vegetation. In both vectors, biting patterns denoted a typical diurnal pattern with two peaks of host-seeking and biting activity in the morning and afternoon. Conclusions: The majority (80%) of the larval habitats were artificial containers. The use of larvicides for vector control as the prominent measure is questionable since applying these chemicals may target only 20% of the total breeding grounds, which are permanent. The resting places of adult mosquitoes are mainly indoors. Therefore, using thermal space spraying of insecticide may not be appropriate, and indoor residual spraying is recommended as a suitable intervention to target adult mosquitoes. This study warrants a holistic vector control approach for all medically important mosquitoes and insects, ensuring the rational use of finance and resources.
Breeding habitat distribution of medically important mosquitoes in Kurunegala, Gampaha, Kegalle, and Kandy districts of Sri Lanka and potential risk for disease transmission: A Cross-sectional study
(Hindawi Pub. Corp., 2020) Ranasinghe, K.; Gunathilaka, N.; Amarasinghe, D.; Udayanga, L.
ABSTRACT: Some arbovirus infections, especially dengue, have increased rapidly over the last few decades in Sri Lanka. Prevalence and distribution of different mosquito species have been limitedly documented, which remains grossly inadequate in providing evidence for potential health risks. In this study, the diversity and species composition of mosquitoes in four selected districts in Sri Lanka (Kurunegala, Gampaha, Kegalle, and Kandy) were investigated. Entomological surveys were conducted from a total of 160 temporary and permanent mosquito breeding habitats identified in the study area from June 2017 to October 2018. Mosquito immature stages were sampled using standard dipping, siphoning, or pipetting methods and identified up to the species level. Percentage relative abundance and habitat characteristics such as species richness, dominance, and Shannon-Weiner diversity were calculated for each surveyed habitat type. Associations between co-occurring species were estimated by Hulbert's coefficient of interspecific association (C8). A total of 4663 mosquito larvae belonging to seven genera and fifteen species of mosquitoes were collected. The relative distribution of mosquito species differed significantly among the four studied districts (X 2 = 143.248; df = 33; P < 0.001). According to Kruskal-Wallis statistics (P < 0.05 at 95% of significance), all diversity indices for immature stages of medically important mosquitoes varied significantly across different breeding sites. Paddy fields had the significantly highest species richness of 4.0 ± 2.82. The coefficients of interspecific association among all the recorded medically important vector mosquitoes were found negative during the present study. The findings of the current study would be useful to identify the entomological potential for disease transmission and facilitate the implementation of appropriate vector control interventions. This would ultimately provide an avenue to improve the personal skills of health staff rather than limiting their knowledge to specified disease vectors, under which the control program is concerned.
Breeding sites of Phlebotomine sand flies in cutaneous leishmaniasis disease endemic areas of the Kurunegala District in Sri Lanka
(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Wijerathna, T.; Gunathilaka, N.; Gunawardena, K.; Rodrigo, W.
Leishmaniasis is a disease transmitted by the bite of infected female sand flies. Disease control largely depends on the knowledge on natural breeding sites of sand flies. In Sri Lanka, only limited information is available on microhabitats of immature sand flies. Therefore, the present study was conducted to identify natural breeding habitats of sand flies in three cutaneous leishmaniasis endemic areas, namely; Galgamuwa, Polpithigama and Maho in the Kurunegala District of Sri Lanka. Study areas were selected based on the number of patients reported to respective Medical Officer of Health (MOH) during the year 2013 - 2016. A preliminary survey was conducted in April 2017 and possible breeding sites were identified for the survey based on field investigations and previous literature. A breeding habitat checklist was prepared for main habitat categories. Field investigations for immature stages were conducted on a monthly basis from May 2017 - June 2018. Three soil samples were collected randomly from each potential breeding habitat and transported to the laboratory. The soil samples were divided into equal portions, and immature stages of sand flies in one portion were screened by direct microscopic examination and sugar flotation method. The rest of the soil samples were incubated at 260C and 75-80% Relative Humidity (RH) under confined laboratory conditions for adult emergence. Adult sand flies were identified using morphological identification keys. A total of 433 potential breeding sites were surveyed under 21 habitat categories. Of them, soil mounds were predominant (n=51) followed by leaf litter (n=46), termite hills (n=42) and tank/river margins (n=36). However, only four habitat types were positive for immature stages of Phlebotomus argentipes, namely; paddy fields (n=5/10), moist soil in dried tanks (n=2/12), soil beneath decaying organic matter (n=2/7) and cattle huts (n=1/23). All positive sites were enriched with organic matter containing moderate moisture levels. However, further studies are required to understand the physiochemical parameters of breeding sites and by that minimize the sand fly population through management of habitat conditions.
Canine filaria species in selected lymphatic filariasis endemic and non-endemic areas in Sri Lanka
(Springer International, 2022) Rathnayake, S.; Chandrasena, N.; Wijerathna, T.; Mallawarachchi, H.; Gunathilaka, N.
Subperiodic brugian filariasis and dirofilariasis show a rising trend in Sri Lanka posing a threat to public health. As information was limited on canine filaria species in Sri Lanka, we studied the filaria parasites among dog populations in lymphatic filariasis (LF) endemic and non-endemic regions by microscopy and molecular methods. Thick blood smears (TBSs) were performed among 295 dogs presenting to veterinary clinics for surgical or sterilization procedures in Galle (LF endemic) and Mullaitivu (LF non-endemic) districts, of which 55.6% were positive for any microfilariae. We identified Dirofilaria repens (50.8%) and Brugia spp. (20.6%) by microscopy, which, included mono-infections (D. repens 35.3% and Brugia spp. 5%) and co-infections (15.6%). Infections in Galle and Mullaitivu were 61% and 44.9% respectively. The brugian filariasis rate was significantly higher among canines in LF endemic Galle district (29.9%) than in Mullaitivu (LF non-endemic) (1.1%) (P < 0.001), while D. repens infections were comparable in both districts. Genomic DNA extracted from 10% of microfilariae positive TBSs was amplified using pan-filarial primers targeting the internal-transcriber-spacer region-2 (ITS-2). Sequencing of amplicons confirmed the presence of D. repens (89.28%), Brugia pahangi (7.14%) and B. malayi (3.57%) infections. The phylogeny constructed and analysed in MEGA X indicated genetic variability among D. repens and B. pahangi isolates from Sri Lanka. With this study, we were able to report B. pahangi infections for the first time in Sri Lanka.
A Challenge for a unique dengue vector control programme: Assessment of the spatial variation of Insecticide resistance status amongst Aedes aegypti and Aedes albopictus populations in Gampaha District, Sri Lanka
(BioMed Central, 2021) Dalpadado, R.; Gunathilaka, N.; Amarasinghe, D.; Udayanaga, L.
BACKGROUND: To date, dengue is considered an important public health problem in Sri Lanka. Irrational use of insecticides without evidence-based applications has primed the development of resistance in mosquito vectors. METHOD: The present study investigated the resistance status of Aedes aegypti and Aedes albopictus to commonly used insecticides in three selected Medical Officer of Health (MOH) areas (i.e., Attanagalla, Dompe, and Negombo) in Gampaha District, Western Province of Sri Lanka. Entomological surveys were performed using ovitraps and larval collections. Larval bioassays were carried out to determine the LC50, LC90, and LC95 and susceptibility status for organophosphate temephos, whereas adult bioassays were performed to test the 0.03% deltamethrin and 0.8% malathion susceptibility. RESULTS: The study revealed that the temephos concentrations required to control Ae. aegypti (13.7-17.7 times) and Ae. albopictus (4.6-7.6 times) are higher than the diagnostic concentration (0.012 mg/L) proposed by the World Health Organization. The highest resistance levels were observed for both Ae. aegypti (14 ± 1.87) and Ae. albopictus (36 ± 1.87) collected from the Negombo MOH area. Therefore, the WHO recommended diagnostic concentration is no longer effective in controlling Ae. aegypti and Ae. albopictus larvae in these areas. Both the dengue vectors have evolved a high level of insecticide resistance to malathion and deltamethrin in the Gampaha District except Ae. albopictus mosquitoes in rural areas. Further, vectors in rural areas are indicated susceptible (>98%) to pyrethroids and emergence of resistance (<97%) for organophosphate insecticides. CONCLUSION: The results of this study warrant the vector management authorities on the proper application of insecticides and rational use in vector control. The susceptibility status of vector mosquitoes should be continuously monitored especially in dengue-endemic areas parallel to the routine surveillance programme. Further molecular studies are strongly recommended to determine the Knockdown Resistance (kdr) mutations among Aedes populations.
Climate change induced vulnerability and adaption for dengue incidence in Colombo and Kandy districts: the detailed investigation in Sri Lanka
(BioMed Central., 2020) Udayanga, L.; Gunathilaka, N.; Iqbal, M. C. M.; Abeyewickreme, W.
BACKGROUND: Assessing the vulnerability of an infectious disease such as dengue among endemic population is an important requirement to design proactive programmes in order to improve resilience capacity of vulnerable communities. The current study aimed to evaluate the climate change induced socio-economic vulnerability of local communities to dengue in Colombo and Kandy districts of Sri Lanka. METHODS: A total of 42 variables (entomological, epidemiological, meteorological parameters, land-use practices and socio-demographic data) of all the 38 Medical Officer of Health (MOH) areas in the districts of Colombo and Kandy were considered as candidate variables for a composite index based vulnerability assessment. The Principal Component Analysis (PCA) was used in selecting and setting the weight for each indicator. Exposure, Sensitivity, Adaptive Capacity and Vulnerability of all MOH areas for dengue were calculated using the composite index approach recommended by the Intergovernmental Panel on Climate Change. RESULTS: Out of 42 candidate variables, only 23 parameters (Exposure Index: six variables; Sensitivity Index: 11 variables; Adaptive Capacity Index: six variables) were selected as indicators to assess climate change vulnerability to dengue. Colombo Municipal Council (CMC) MOH area denoted the highest values for exposure (0.89: exceptionally high exposure), sensitivity (0.86: exceptionally high sensitivity) in Colombo, while Kandy Municipal Council (KMC) area reported the highest exposure (0.79: high exposure) and sensitivity (0.77: high sensitivity) in Kandy. Piliyandala MOH area denoted the highest level of adaptive capacity (0.66) in Colombo followed by Menikhinna (0.68) in Kandy. The highest vulnerability (0.45: moderate vulnerability) to dengue was indicated from CMC and the lowest indicated from Galaha MOH (0.15; very low vulnerability) in Kandy. Interestingly the KMC MOH area had a notable vulnerability of 0.41 (moderate vulnerability), which was the highest within Kandy. CONCLUSIONS: In general, vulnerability for dengue was relatively higher within the MOH areas of Colombo, than in Kandy, suggesting a higher degree of potential susceptibility to dengue within and among local communities of Colombo. Vector Controlling Entities are recommended to consider the spatial variations in vulnerability of local communities to dengue for decision making, especially in allocation of limited financial, human and mechanical resources for dengue epidemic management. KEYWORDS: Climate change; Dengue; Sri Lanka; Vulnerability.
Clinicopathological Profile of Cutaneous Leishmaniasis in Army Personnel in the Kilinochchi and Mulllativu Districts of Sri Lanka
(Sri Lanka Medical Association, 2020) Wijesinghe, H.D.; Gunathilaka, N.; Semege, S.; Pathirana, K.P.N.; Manamperi, N.; de Silva, M.V.C.; Fernando, S.D.
INTRODUCTION AND OBJECTIVES: Leishmaniasis is caused by an intra cellular protozoan of the genus Leishmania. The clinicopathological profile of cutaneous leishmaniasis (CL) varies according to the species. Leishmania donovani is the causative organism for leishmaniasis in Sri Lanka. This study describes the clinicopathological features of cutaneous leishmaniasis among army personnel serving in two Northern districts of the country. METHODS: In this collaborative cross-sectional study, the histopathology of fifty cases of CL confirmed by at least two methods (slit skin smear, lesion aspirate, tissue impression and histology) were reviewed. The parasitic load was assessed semi-quantitatively. The histological features were correlated with the clinical presentation and organism load. RESULTS: The majority (89.8%; n=44) presented with a single lesion mostly located in the upper limb (69.4%, n=34). The lesion types included papule (34.7%, n=17), nodule (32.7%, n=16) and ulcer (30.6%, n=15). Evolution time of lesions averaged 31.55 weeks. Epidermal changes were observed in 49 and included hyperkeratosis (90.0%; n=45), acanthosis (44.0%; n=22), atrophy (34.0%; n=17) and interface change (66%; n=33). Dermal changes were seen in all cases and characterized by a lymphohistioplasmacytic inflammatory infiltrate of variable intensity with ill-formed granuloma in 19 cases (38%) and well-formed epithelioid granulomas in 22 cases (44%). Focal necrosis was present in 20 % (n=10). Leishmania amastigote forms were observed in 88% (n=44). Transepidermal elimination (P=0.025), granuloma (P=0.027) formation and type of lesion (P=0.034) were significantly associated with organism load with granuloma formation being associated with reduction in organism load. CONCLUSION: Histopathological changes were characterised by a diffuse lymphohistioplasmacytic infiltrate, ill-defined granuloma or well-formed granuloma. Well-formed granulomata were associated with a reduction in organism load.
Comparative analysis of the larvicidal activity of temephos (EC50) and novaluaron (EC10) to control Anopheles stephensi in Sri Lanka
(Elsevier, 2023) Jude, J.; Gunathilaka, N.; Udayanga, L.; Fernando, D.; Premarathne, P.; Wickremasinghe, R.; Abeyewickreme, W.
Background: Anopheles stephensi was first recorded in the coastal area of Mannar District, Sri Lanka, in December 2016. Since then, this vector has been isolated from other districts in the Northern and Eastern Provinces of Sri Lanka. Chemical control is the main arm of vector control that can be used to reduce the vector densities within a short period. Thus, the present study aimed at evaluating the efficacy of using selected insecticides for the control of An. stephensi larvae. Method: The third and fourth instar larval stages of An. stephensi (F2 generation) of field mosquitoes that were caught using cattle baited net trap collections from Columbuthurai, Kurunagar, and Navanthurai areas in Jaffna District, Sri Lanka, were obtained from the laboratory colony established at Jaffna. Batches of 100 larvae were taken for experiments and introduced separately to a concentration series of temephos and novaluron (0.04-400 ppm). A control test was also performed at each setup without introducing insecticides. The mortality rates of An. stephensi larvae exposed to different concentrations of larvicides were recorded at 1, 24 and 48-h intervals. The experiment was replicated five times at individual concentrations for each selected chemical. Data were analyzed using the General Linear Model (GLM) and Probit analysis. Results: The highest mortality rate (100%) at a 1-h exposure period was observed from temephos at >100 ppm. The mortality rates varied significantly for different concentrations and larvicides (p < 0.05). At 24-h of the exposure period, the 100% mortality of An. stephensi larvae were observed from both temephos and novaluron even at 0.04 ppm. Conclusion: Both temephos and novaluron reported 100% mortality rates in An. stephensi larvae at 1-h and 24-h exposure periods. Based on the findings, temephos and novaluron can be recommended as effective larvicides for chemical-based control of An. stephensi in Jaffna, Sri Lanka. Further, it is recommended to conduct a field-based study, where habitat types and water quality are highly heterogeneous and may affect the residual activity.
A Comprehensive analysis on abundance, distribution, and bionomics of potential malaria vectors in Mannar District of Sri Lanka
(Hindawi Publishing Corporation, 2019) Gunathilaka, N.; Hapugoda, M.; Wickremasinghe, R.; Abeyewickreme, W.
BACKGROUND:A detailed knowledge of the distribution of the malaria vectors in Mannar district of Sri Lanka has not been studied after 1927. Past records indicated the presence of only seven species of anophelines, namely, An. culicifacies, An. subpictus, An. barbirostris, An. peditaeniatus, An. nigerrimus, An. Jamesii, and An. maculatus. There have been many changes in terms of distribution of Anopheles in the district over time. METHODS: Entomological surveillance was conducted on a monthly basis, comprising indoor hand collection, window trap collection, cattle-baited net collection, cattle-baited hut collection, and larval survey from June 2010 to June 2012 in 12 study areas under three entomological sentinel sites. The relationship between seven abiotic variables of the breeding habitats was measured. Pearson's correlation coefficients were used to determine the associations between climatic variables and anopheline densities. RESULTS:A total of 74,181 mosquitoes belonging to 14 Anopheles species were recorded. An. subpictus was the most predominant species from all techniques representing 92% (n=68,268) of the total anopheline collection. However, Anopheles culicifacies was not recorded from any site during the study period. Larval surveys identified 12 breeding habitat categories including waste water collections, lagoon water collections, and drains which were not recorded as breeding habitats by previous studies. The mean dissolved oxygen level of waste water collections was 3.45±0.15 mg/l. The mean salinity and conductivity of lagoon water collections were 21105±1344 mg/l and 34734±1974 μs/cm, respectively.CONCLUSION: The present study provides the updated knowledge on anopheline distribution and vector bionomics. Therefore, documentation of the current knowledge would be useful for learners and health authorities to design appropriate vector control measures in the prevention of reintroduction of malaria.
Comprehensive evaluation of demographic, socio-economic and other associated risk factors affecting the occurrence of dengue incidence among Colombo and Kandy Districts of Sri Lanka: a cross-sectional study
(BioMed Central, 2018) Udayanga, L.; Gunathilaka, N.; Iqbal, M.C.M.; Lakmal, K.; Amarasinghe, U.S.; Abeyewickreme, W.
BACKGROUND: Comprehensive understanding of risk factors related to socio-economic and demographic status and knowledge, attitudes and practices (KAP) of local communities play a key role in the design and implementation of community-based vector management programmes, along with the identification of gaps in existing control activities. METHODS: A total of 10 Medical Officers of Health (MOH) areas recording high dengue incidence over the last five years were selected from Colombo (n = 5) and Kandy (n = 5) Districts, Sri Lanka. From each MOH area, 200 houses reporting past dengue incidence were selected randomly as test group (n = 1000 for each district) based on the dengue case records available at relevant MOH offices. Information on socio-economic and demographic status and knowledge, attitudes and practices were gathered using an interviewer administered questionnaire. The control group contained 200 households from each MOH area that had not reported any dengue case and the same questionnaire was used for the assessment (n = 1000 for each district). Statistical comparisons between the test and control groups were carried out using the Chi-square test of independence, cluster analysis, analysis of similarities (ANOSIM) and multi-dimensional scaling (MDS) analysis. RESULTS: Significant differences among the test and control groups in terms of basic demographic and socio-economic factors, living standards, knowledge, attitude and practices, were recognized (P < 0.05 at 95% level of confidence). The test group indicated similar risk factors, while the control group also shared more or less similar characteristics as depicted by the findings of cluster analysis and ANOSIM. Findings of the present study highlight the importance of further improvement in community education, motivation and communication gaps, proper coordination and integration of control programmes with relevant entities. Key infrastructural risk factors such as urbanization and waste collection, should be further improved, while vector controlling entities should focus more on the actual conditions represented by the public on knowledge, attitudes and personal protective practices. CONCLUSIONS: The design of flexible and community friendly intervention programmes to ensure the efficacy and sustainability of controlling dengue vectors through community based integrated vector management strategies, is recommended.
Comprehensive evaluation of demographic,socio-economic and other associated risk factors affecting the occurrence of dengue incidence among Colombo and Kandy Districts of Sri Lanka: a cross-sectional study
(Parasites & Vectors (2018) 11:478, 2018) Udayanga, L.; Gunathilaka, N.; Iqbal, M.C.M.; Lakmal, K.; Amarasinghe, U.S.; Abeyewickreme, W.
Background: Comprehensive understanding of risk factors related to socio-economic and demographic status and knowledge, attitudes and practices (KAP) of local communities play a key role in the design and implementation of community-based vector management programmes, along with the identification of gaps in existing control activities. Methods: A total of 10 Medical Officers of Health (MOH) areas recording high dengue incidence over the last five years were selected from Colombo (n = 5) and Kandy (n = 5) Districts, Sri Lanka. From each MOH area, 200 houses reporting past dengue incidence were selected randomly as test group (n = 1000 for each district) based on the dengue case records available at relevant MOH offices. Information on socio-economic and demographic status and knowledge, attitudes and practices were gathered using an interviewer administered questionnaire. The control group contained 200 households from each MOH area that had not reported any dengue case and the same questionnaire was used for the assessment (n = 1000 for each district). Statistical comparisons between the test and control groups were carried out using the Chi-square test of independence, cluster analysis, analysis of similarities (ANOSIM) and multidimensional scaling (MDS) analysis. Results: Significant differences among the test and control groups in terms of basic demographic and socio-economic factors, living standards, knowledge, attitude and practices, were recognized (P < 0.05 at 95% level of confidence). The test group indicated similar risk factors, while the control group also shared more or less similar characteristics as depicted by the findings of cluster analysis and ANOSIM. Findings of the present study highlight the importance of further improvement in community education, motivation and communication gaps, proper coordination and integration of control programmes with relevant entities. Key infrastructural risk factors such as urbanization and waste collection, should be further improved, while vector controlling entities should focus more on the actual conditions represented by the public on knowledge, attitudes and personal protective practices. Conclusions: The design of flexible and community friendly intervention programmes to ensure the efficacy and sustainability of controlling dengue vectors through community based integrated vector management strategies, is recommended.
Delayed anxiety and depressive morbidity among dengue patients in a multi-ethnic urban setting: first report from Sri Lanka
(BioMed Central, 2018) Gunathilaka, N.; Chandradasa, M.; Champika, L.; Siriwardana, S.; Wijesooriya, L.I.
BACKGROUND: Although the physical consequences of dengue are well documented, delayed psychological co-morbidities are not well studied to date. Therefore, the objective of the present study was to determine the prevalence of depressive, anxiety and stress symptoms among past dengue patients. METHODS: A community-based, case-control study in a multi-ethnic urban setting was conducted in Sri Lanka involving adults who were diagnosed to have dengue fever by a positive dengue IgM antibody response between 6 and 24 months ago. Self-administered Depression, Anxiety and Stress Scale (DASS-21), Centre for Epidemiological Studies Depression Scale (CESD-20) and a structured clinical interview by a psychiatrist were done in the patients and in an age and gender-matched control group. RESULTS: Fifty-three participants each in the patient (mean age 42.9 years, SD 15.5) and control (mean age 41.6 years, SD 15.3) groups were surveyed. The ages ranged from 18 to 70 years and 64.2% were females. The majority (90.6%; n = 48) of the individuals had been diagnosed with dengue fever followed by dengue haemorrhagic fever (9.4% n = 5). Denguepatients had higher DASS-21 mean depressive scores (means 11.7/9.4, SD 6.4/4.0, t = 2.2, p = .028), anxiety scores (means 10.7/7.2, SD 6.8/1.8, t = 3.6, p = .0005), stress scores (means 12.0/8.8, SD 5.3/3.5, t = 3.6, p = .0004) and CESD-20 scores (means 16.1/11.7, SD 9.4/7.3, t = 2.6, p = .008) than controls. The DSM-5 depressive disorder was clinically detected by the psychiatrist among 15.1 and 7.5% in patient and control groups (OR 2.1; CI .5-7.7; p = .22). Limitations: a limitation is the small sample size. CONCLUSION: Patients with past dengue had significantly higher depressive, anxiety and stress symptoms than the control group according to the DASS-21 and CESD-20 tools. To our knowledge, this is the first report on delayed psychological morbidity related to dengue. This may warrant healthcare professionals to incorporate mental counselling for dengue patients.
Dengue prediction modelling and development of area-specific thresholds for epidemic management in urban settings of Gampaha district, Sri Lanka
(International Research and Innovation Symposium on Dengue amidst the Pandemic, 2022) Dalpadado, R.; Amarasinghe, D.; Gunathilaka, N.; Wijayanayake, A.
Introduction and objectives The growing global threat of dengue in both endemic and non-endemic countries have shifted the attention to establishing an early warning system to assist in dengue control and effectively allocating scarce public health resources to manage outbreaks. Thus, the current study was designed to develop localized thresholds to aid in sustainable dengue vector control measures in three Medical Officer of Health (MOH) areas (Negombo, Wattala, Kelaniya) in the Gampaha District. Method The cross-correlation function analysis (CCF) was performed to check the effects of climatic variables (average rainfall, rainy days, average temperature, humidity) and Breteau Index (BI) with dengue case incidence from 2014 to 2019. The dengue incidence at time t, BIs with a one-month lag; Aedes aegypti; BIA(t-1), Aedes albopictus; BIB (t-1) and monthly average rainfall; RFavg (t-2), rainy days; RD (t-2), Average relative humidity; RHavg (t-2) at twomonth lag and monthly average temperature; Tavg at three-month lag were checked. Areaspecific thresholds were derived from multiple linear regression. The model was validated for the Jaela MOH area for the same period. Results Stepwise regression has excluded temperature, rainfall and BIB in urban areas and a statistically significant strong association (r= 0.775) was displayed with BIA(t-1) and RHavg(t-2). When the incidence of the cases exceeded 25, it reached an alarming situation while exceeding 44 was classified as an epidemic in urban areas. BIA>1, RHavg >85%, BIA>2; RHavg>81%, the model implies an early outbreak scenario and when BIA >3; RHavg > 88%, BI>4; RHavg>84%, BIA>5; RHavg>81%, and whenever BIA > 6; RHavg>77% it reached up to severe epidemics. The model accurately predicted all outbreaks in the Jaela MOH area. International Research and Innovation Symposium on Dengue amidst the Pandemic 63 Conclusions and recommendations The common thresholds utilized for vector control entities remain ineffective and cannot be applied throughout the country. Therefore, early warning indications can plan a prior month source reduction in a low-risk zone. In contrast, government-led source reduction programs should be maximized and an intense integrated vector control method must be implemented before it reaches an epidemic.