Medicine
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This repository contains the published and unpublished research of the Faculty of Medicine by the staff members of the faculty
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Item The presence of strongyloidiasis and associated risk factors in patients undergoing treatment at the National Cancer Institute, Maharagama, Sri Lanka(Sri Lanka Medical Association, 2023) Weerasekera, C.J.; Menike, C.W.; Wimalasiri, U.; Wijerathna, T.; Jayathilake, D.C.C.; Somawardane, U.A.B.P.; Saravanamuttu, U.; Yoganathan, N.; Perera, N.; Gunathilaka, N.; de Silva, N.R.; Wickremasinghe, D.R.INTRODUCTION: Strongyloides stercoralis can cause severe disease in the immunocompromised. Without a proper gold-standard diagnostic technique, strongyloidiasis is scarcely studied both globally and locally. OBJECTIVES: We aimed to estimate the prevalence of strongyloidiasis among immunocompromised adult patients and to identify risk factors. METHODS: This study was carried out between February to October 2022. A faecal sample and 2 ml of venous blood were collected from consented patients. Direct faecal smear, agar plate, Harada-Mori and Charcoal cultures were performed on the faecal samples. Qualitative Polymerase Chain Reaction (PCR) was performed on selected faecal samples using S. stercoralis targeting ITS1 region. Strongyloides IgG ELISA was carried out on the serum samples using DRG Strongyloides IgG ELISA kit. RESULTS: Collectively, 144 patients (males = 68, females = 76) provided blood/faecal sample or both. Relevant to strongyloidiasis-associated symptoms, some patients had diarrhoea (n=12) and eosinophilia (n=11). Some of them (n=74) had occupational or recreational exposure to soil as potential risk factors. Overall, 24 patients were positive for strongyloidiasis from one or more diagnostic method (5 PCR and 19 ELISA). There were zero culture or direct smear positives. There was no significant association between disease positivity with either of the clinical features or risk factors. CONCLUSION: The prevalence of strongyloidiasis in patients with malignancies was 16.66%. Strongyloidiasis is existent in the immunocompromised in Sri Lanka even in the absence of suggestive clinical features or regular exposure to risk factors. Screening immunocompromised patients with sensitive techniques such as PCR for timely diagnosis and treatment is recommended.Item Genetic diversity of Leishmania donovani isolates from cutaneous lesions of military personnel in the Mullaitivu and Kilinochchi districts of the Northern Province, Sri Lanka(Wolters Kluwer, 2022) Wijerathna, T.; Gunathilaka, N.; Semege, S.; Pathirana, N.; Rodrigo, W.; Fernando, D.Objective: To compare the DNA sequences of Leishmania (L.) donovani isolated from individuals in two districts of the Northern Province with other parts of Sri Lanka and neighboring countries. Methods: Samples were collected from military personnel at the Army Hospital, Narahenpita, Sri Lanka from November 2018 to March 2020. A portion of the samples was fixed, stained with Giemsa and observed under the light microscope. The genomic The DNA was extracted from the remaining portion of the samples using DNEasy blood tissue kit (Qiagen, Germany) and amplified using Leishmania genus-specific primers for molecular diagnosis initially. DNA was amplified using L. donovani species-specific primers by PCR and the amplified product was sequenced for comparison of nucleotide sequences. Results: Out of 76 suspected patients, at least one biological sample of 45 (59.2%) was positive for L. amastigotes upon microscopy. Overall, 33 (43.4%) were positive in Leishmania genus-specific PCR, but only 23 (30.3%) were positive in L. donovani specific PCR. The dendrogram indicates that the current sequences clustered together with those from Nepal and Gampaha districts (Western Province), Sri Lanka, while the Indian and Eastern African sequences clustered separately. Conclusions: The genetic diversity was low among the isolates, indicating a single and possibly a local point of origin. However, the similarity of Sri Lankan and Nepal strains indicate a possibility of a shared point of origin, which needs more extensive evidence to confirm.Item Time series analysis of leishmaniasis incidence in Sri Lanka: evidence for humidity-associated fluctuations(Springer Verlag, 2023) Wijerathna, T.; Gunathilaka, N.Leishmaniasis is a vector-borne disease of which the transmission is highly influenced by climatic factors, whereas the nature and magnitude differ between geographical regions. The effects of climatic variables on leishmaniasis in Sri Lanka are poorly investigated. The present study focused on time-series analysis of leishmaniasis cases reported from Sri Lanka with selected climatic variables. Variance stabilized time series of leishmaniasis patients of entire Sri Lanka and major districts from 2014 to 2018 was fitted to autoregressive integrated moving average (ARIMA) models. All the possible models were generated by assigning different values for autoregression and moving average terms using a function written in R statistical program. The top ten models with the lowest Akaike information criterion (AIC) values were selected by writing another function. These models were further evaluated using RMSE and MAPE error parameters to select the optimal model for each area. Cross-autocorrelation analyses were performed to assess the associations between climate and the leishmaniasis incidence. Most associated lags of each variable were integrated into the optimal models to determine the true effects imposed. The optimal models varied depending on the area. SARIMA (0,1,1) (1,0,0)12 was optimal for the country level. All the forecasts were within the 95% confidence intervals. Humidity was the most notable factor associated with leishmaniasis, which could be attributed to the positive impacts on sand fly activity. Rainfall showed a negative impact probably as a result of flooding of sand fly larval habitats. The ARIMA-based models performed well for the prediction of leishmaniasis in the short term.Item Genetic variation of sand flies (Diptera: Psychodidae) in Gampaha and Kurunegala districts of Sri Lanka: Complementing the morphological identification(Wolters Kluwer Medknow Publications, 2022) Wijerathna, T.; Gunathilaka, N.; Rodrigo, W,OBJECTIVE: To identity the variation of sand flies in the Gampaha and Kurunegala districts of Sri Lanka and to assess DNA barcoding as a complementing method for morphological identification. METHODS: A total of 38 441 sand flies were collected from selected localities in Gampaha and Kurunegala districts using standard entomological techniques from May 2017 to December 2018. Specimens were identified using morphological features and compared with mitochondrial cytochrome C oxidase subunit I gene- based DNA barcoding as an alternative tool. RESULTS: Morphological and molecular identification confirmed the presence of four species under two genera (Phlebotomus and Sergentomyia). Phlebotomus argentipes was the predominant species, followed by Sergentomyia (S.) punjabensis, S. babu insularis, and an unidentified Sergentomyia sp. Phlebotomus argentipes showed a clear genetic differentiation from other species. S. babu insularis and S. punjabensis showed a higher genetic affinity to each other than the unidentified species. The unidentified Sergentomyia species is morphologically similar to S. zeylanica, but differs only in clavate gonostyle. CONCLUSIONS: DNA barcoding is an effective technique for the identification of sand flies. Further studies using molecular techniques will improve the knowledge of the cryptic diversity of Sri Lankan sand fly fauna. Establishing a reliable and standardized identification system for sand fly species in Sri Lanka is recommended.Item Detection of Leishmania donovani DNA within field-caught Phlebotomine Sand Flies (Diptera: Psychodidae) in three cutaneous leishmaniasis endemic foci of Kurunegala District, Sri Lanka(Hindawi Pub. Corp., 2021) Wijerathna, T.; Gunathilaka, N.; Gunawardena, K.; Fujii, Y.; Gunasekara, D.ABSTRACT: Leishmaniasis is a parasitic infection transmitted through the bite of female phlebotomine sand flies. Microscopy is the gold standard to detect parasites within the sand flies and for vector incrimination. However, molecular-based detection has become more popular nowadays in the identification of Leishmania parasites since it provides detection and species identification simultaneously with no need of laborious procedures. The entomological surveys were conducted monthly from May to October 2017 using standard entomological techniques. Field-caught sand flies were identified to the species level followed by DNA extraction. The polymerase chain reaction (PCR) was performed using species-specific primers to detect Leishmania donovani parasites. A total of 1,662 sand flies were encountered from the entomological surveys, and the majority of them were Phlebotomus argentipes (n = 1517; 91.27%), while others were Sergentomyia punjabiensis (n = 140; 8.72%). Leishmania donovani parasite DNA was detected only from P. argentipes (2.3%; n = 2). The detection of Leishmania DNA in P. argentipes suggests the possible role of this species as a vector for leishmaniasis in Sri Lanka.Item The Diversity of midgut bacteria among wild-caught Phlebotomus argentipes (Psychodidae: Phlebotominae), the Vector of leishmaniasis in Sri Lanka(Hindawi Pub. Co., 2020) Gunathilaka, N.; Perera, H.; Wijerathna, T.; Rodrigo, W.; Wijegunawardana, N.D.A.D.ABSTRACT: Phlebotomus argentipes is the main suspected vector for leishmaniasis in Sri Lanka. Investigations on the presence of aerobic bacteria in the gut of sand flies which evidence a potential approach to control leishmaniasis transmission through a paratransgenic strategy are still not available for the local sand fly populations. Field-caught unfed female sand flies collected from three selected Medical Officer of Health (MOH) areas (Polpithigama, Maho, and Galgamuwa) in Kurunegala District, Sri Lanka from August to December 2018 were used. Prokaryotic 16S ribosomal RNA partial gene was amplified and sequenced. Morphological identification revealed the presence of only one sand fly species, P. argentipes (n = 1,969). A total of 20 organisms belonging to two phyla (Proteobactericea and Furmicutes) were detected within the gut microbial community of the studied sand fly specimens. This study documents the first-ever observation of Rhizobium sp. in the midgut of P. argentipes. The presence of Bacillus megaterium, which is considered as a nonpathogenic bacterium with potential use for paratransgenic manipulation of P. argentipes suggest that it may be used as a delivery vehicle to block the vectorial transmission of Leishmania parasites. In addition, Serratia marcescens may be used as a potential candidate to block the parasite development in sand fly vectors since it has evidenced antileishmanial activities in previous investigations. Hence, further studies are required to gain full insight into the potential use of this bacterium in the control of Leishmania parasites through paratransgenesis.Item Descriptive Investigation of Strongyloidiasis Infection and Characterization of Strongyloides stercoralis Using Morphological and Molecular-Based Methods(Hindawi Pub. Corp., 2020) Gunathilaka, N.; Chandrasena, N.; Wijerathna, T.; Fuji, Y.; Gunasekara, D.; Gunatilaka, R.P.; Premaratna, R.ABSTRACT: Strongyloidiasis is caused by the nematode Strongyloides stercoralis which has the unique ability to reproduce and complete its entire life cycle within the human host through its autoinfection cycle. Diagnosis of this infection is important because of its potential to cause fatal hyperinfection syndrome or disseminated infections in those with defective cellular immunity. Parasitological methods based on faecal microscopy and culture often fail to detect low-intensity infections. A multiplex polymerase chain reaction (PCR) assay was developed for the detection of S. stercoralis, Ascaris lumbricoides, and Enterobius vermicularis by designing primers specific for the ITS1 region of ribosomal DNA of S. stercoralis and A. lumbricoides and 18S region of rRNA of E. vermicularis. A 61-year-old patient presented with chronic gastrointestinal and respiratory symptoms and weight loss with a stool microscopy positive for helminth larvae. Stool cultures with the Harada-Mori technique yielded L3 larvae which were identified as S. stercoralis based on morphology. The multiplex PCR performed on DNA extracted from stool elicited the expected band at 129 bp on gel electrophoresis of the PCR yield providing molecular evidence of intestinal strongyloidiasis. The patient's gastrointestinal symptoms improved with a six-day course of albendazole (400 mg twice daily). Negative posttreatment stool microscopy, culture, and PCR confirmed successful clearance of infection. Molecular-based PCR assay is a promising tool to diagnose and assess the therapeutic efficacy of anthelmintics in intestinal helminthiases such as strongyloidiasis.Item Morphological identification keys for adults of sand flies (Diptera: Psychodidae) in Sri Lanka(BioMed Central, 2020) Wijerathna, T.; Gunathilaka, N.BACKGROUND: Phlebotomine sand flies are a medically important group of insects that is responsible for the transmission of leishmaniasis. Surveillance plays a major role in vector control programmes through exploring species abundance, potential entomological risk and designing appropriate control measures. In field surveillance programmes of such nature, morphological identification of vector species is of paramount importance. However, in Sri Lanka, there is no published taxonomic key available for the identification of leishmaniasis vectors. METHOD: Identification keys for both male and females of the sand flies recorded in Sri Lanka were developed using morphological features. Main identification features were compared with the original observation of specimens collected from surveys and the use of published literature. Photographic illustrations of morphological features are included with the intention of making the keys user-friendly for non-taxonomists. RESULTS: A total of 22 sand fly species (Diptera: Psychodidae) of the genera Phlebotomus and Sergentomyia reported in Sri Lanka from 1910 to 2019 are included in the present work. CONCLUSION: This simplified key, along with photographs taken from specimens would be beneficial to the health staff, entomologists and research staff who deal with leishmaniasis control programmes and vector-related studies. KEYWORDS: Identification; Morphology; Sand flies; Taxonomy; Vectors.Item Recent developments and future directions in the paratransgenesis based control of Leishmania transmission(Elsevier, 2020) Wijerathna, T.; Gunathunga, S.; Gunathilaka, N.ABSTRACT: Vector-borne diseases are one of the main concerns regarding global health. Among these, leishmaniasis stands as one of the most serious issues. This disease is transmitted via the bite of female phlebotomine sand flies. Due to the drawbacks such as the development of resistance associated with conventional vector control methods, paratransgenesis has become more popular in the recent past. A range of bacteria inhabit the gut of different species of sand flies. Bacillus subtilis, B. megaterium, and Enterobacter cloacae dissolvens are some of the common bacteria with ideal characteristics for this technique. Among the large number of natural anti-microbial peptides (AMPs) recovered from animals, DS hypo-01, Phylloseptin-1 and melittin are found to be the most effective. Hybrids of Cecropin A and melittin such as CA(1–8)M(1–18), D-CA(1–8)M(1–18) and N-Ac-CA(1–8)M(1–18) are also suitable candidates. Use of peptides initially released in an inactive form to activate upon exposure to a specific molecule is a potential solution for the lower specificity of AMPs. Single chain antibodies on the other hand, have high specificity, but effectiveness is lower than AMPs. The genetic transformation of the selected bacteria and the generation of paratransgenic sand flies through transtadial transmission are feasible under laboratory conditions. Safe delivery techniques such as microencapsulation are being tested to increase the specificity reducing environmental issues. Nevertheless, extensive studies with more practical approaches are required before applying this technique in the field. KEYWORDS: Leishmaniasis; Paratransgenesis; Antileishmanial peptides; Gut microbiota; Biological control.Item Diurnal adult resting sites and breeding habitats of Phlebotomine sand flies in Cutaneous Leishmaniasis endemic areas of Kurunegala District, Sri Lanka(BioMed Central, 2020) Wijerathna, T.; Gunathilaka, N.BACKGROUND: Sand flies are responsible for the transmission of several disease pathogens including Leishmania. Sand flies breed in habitats with high levels of humidity and organic matter. They are nocturnal in nature and peak activity ranges from dusk to dawn. The scientific evidence on breeding ecology and diurnal resting sites of sand fly fauna are important aspects of planning and implementing vector control activities. However, such fundamental information is grossly inadequate in Sri Lanka to support the control efforts in the country. Therefore, the present study addresses some of the important aspects of sand fly breeding ecology and diurnal resting sites. METHODS: Potential resting sites were thoroughly observed, and sand flies were collected using a battery-operated aspirator and sticky papers when appropriate from three selected Medical Officer of Health (MOH) areas (Polpithigama, Maho and Galgamuwa) in Kurunegala district, Sri Lanka. Soil samples were collected from each potential breeding site. Half of each soil sample was incubated for 45 days. The other half was screened for immature stages. Adult sand flies collected from field and emerged adults at the insectary under confined incubation were identified using morphological characteristics. RESULTS: Pepper bushes and termite mounds were the most notable resting sites while, betel bushes, cattle huts, piles of coconut shells, latrines, manna bushes and tree holes were also positive for sand fly adults. Only two species, Phlebotomus argentipes and Sergentomyia punjabensis, were reported. Soil samples were collected from a total of 432 sites and 7 of them were positive for immature stages. Predominant breeding habitats identified during the present study were mud flats and moist soils of rice paddies, the soil below decaying hay, drying irrigational tank bottom moist soil, and the floors of cattle huts. CONCLUSIONS: This study demonstrates that the potential adult resting sites and breeding habitats are abundant in the Polpithigama, Maho and Galgamuwa MOH areas. Therefore, vector control activities targeting both adult and immature stages of sand flies are recommended. KEYWORDS: Breeding sites; Leishmaniasis; Resting sites; Sand fly; Sri Lanka.