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This repository contains the published and unpublished research of the Faculty of Medicine by the staff members of the faculty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 Distribution and seasonal variation of malaria vectors in the Mannar and Jaffna Districts; an entomological investigation during the phase of prevention of re-establishment of malaria in Sri Lanka(Springer Link, 2024) Jude, J.; Gunathilaka, N.; Wijerathna, T.; Fernando, D.; Wickremasinghe, R.; Abeyewickreme, W.Sri Lanka has been declared “malaria-free” since 2016. The presence vectors and the cent establishment of new vectors are key challenges. This study documents the distribution of malaria vectors in previously high malaria endemic areas in Sri Lanka. Three locations were selected in Mannar and Jaffna districts. Entomological surveillance was carried out during January 2019 to January 2020 in both districts using cattle baited net (CBNT), hand collection (HC), and larval collection. The variation of mosquito abundance with selected climatic variables were evaluated using Pearson’s correlation. A total of 44,526 anophelines belonging to 12 species was encountered from both districts. The CBNT was the most productive technique that represented 78.65% (n = 35,022) of the total collection. Anopheles subpictus was the predominant species among adult collections in both districts, while in larval surveys, An. stephensi (60.1%; n = 2963) and An. varuna (40.9%; n = 1026) were observed in Jaffna and Mannar districts, respectively. The adult density indicated significantly strong positive correlations to the rainfall (r = 0.619, P < 0.05) and humidity (r = 0.524, P < 0.05) in both Jaffna and Mannar (rainfall: r = 0.553, P < 0.05; humidity: r = 0.553, P < 0.05). The number of larvae was not directly correlated with climatic variables. The present study reports the presence of An. culicifacies, An. subpictus and An. stephensi. Considering the fact that imported malaria cases are reported across the country the fact that there is an entomological risk to transmit malaria locally is a challenge. This warrants the continuous monitoring of vector population and seasonal variation, especially in previous malaria endemic regions.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 The epidemiological trend of cutaneous leishmaniasis in Kegalle district, Sri Lanka: A newly established disease focus and assessment of bioclimatic suitability for disease establishment using ecological niche modelling(Elsevier, 2023) Wijerathna, T.; Wickramasinghe, K.; Gunathilaka, N.; Perera, A.; Bandara, S.Cutaneous leishmaniasis is prevalent in Sri Lanka since 1992. It remains as a health issue with increasing numbers and spreading from endemic to non-endemic areas in the county. Kegalle district is a new disease focus, which notified the first case in 2016. However, there is no documented evidence of the vector distribution, abundance and potential risk factors in this district. Two Medical Officer of Health (MOH) areas (Rambukkana and Warakapola) that had reported the highest numbers of cases in the Kagalle district was selected and recorded cases (2016-2020) were obtained. The patients were visited and socio-economic, demographic, environmental and awareness-related information was collected using an interviewer-administered questionnaire. Entomological surveys were conducted from July 2019- July 2020 using three standard entomological techniques. Bioclimatic suitability for the disease transmission was evaluated using ecological niche modelling. A total of 107 patients were reported from both MOH areas and 88 were recruited for the study. The study showed that leishmaniasis in the Kegalle district progressed to an outbreak level within 3 years after reporting the first case. School students (n = 22, 25%, P < 0.05) and individuals between 11 and 20 years of age (n = 33, 37.5%, P<0.05) were identified as the main risk groups, while the presence of composting sites (n = 65, 73.9%, P < 0.05), abandoned lands (n = 63, 71.6%, P < 0.05) in the surrounding and suboptimal (dark or normal) lighting conditions (n = 87, 98.8%, P < 0.05) in the house were identified as main risk factors. Areas closer to the adjacent district (Kurunegala), which is a known endemic district for leishmaniasis indicated a high probability (0.3-0.5) for disease transmission. Sergentomyia zeylanica (n = 164, 56.94%), was identified as the predominant sand fly species followed by Phlebotomus argentipes (n = 121, 42.01%), Sergentomyia babu insularis (n = 2, 0.69%) and Sergentomyia punjabensis (n = 1, 0.35%). Phlebotomus argentipes was captured mostly for outdoor resting sites and S. zeylanica was recoded from both indoor and outdoor. The presence of vectors that can transmit leishmaniasis in these areas along with the potential risk factors could increase the transmission risk and disease establishment in new areas that are ecologically favourable for disease transmission. Therefore, vector control entities should undertake immediate measures to stop spreading the disease into new areas.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 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.Item Population dynamics of phlebotomine sand flies (Diptera: Psychodidae) in cutaneous leishmaniasis endemic areas of Kurunegala District, Sri Lanka(Elsevier, 2022) Wijerathna, T.; Gunathilaka, N.; Gunawardena, K.; Rodrigo, W.Sand flies are the primary vectors of leishmaniasis. Disease management with effective vector control depends on the knowledge of vector population dynamics. In Sri Lanka, despite few isolated entomological collections, long-term studies are not reported to date. In the reported study, monthly entomological surveillance was conducted from May 2017 to December 2018 in Polpithigama, Maho, and Galgamuwa Medical Officer of Health (MOH) areas using standard entomological techniques. Climatic data were collected from the Department of Meteorology, Sri Lanka. Patient records were collected from each MOH office. A total of 38,339 sand flies were collected. The majority were Phlebotomus argentipes (99.50%, n=38,147), while the rest was Sergentomyia punjabensis (0.50%, n=192). Wind speed reduces sand fly abundance (r= -0.519, P<0.05) evidently by limiting the movement. Rainfall increases sand fly abundance (r= 0.842, P<0.05, lag = 6 months) probably by improving favorable conditions in breeding sites. The actual effect of humidity is not conclusive without further research. The observed higher prevalence of leishmaniasis in the study sites could be due to the higher sand fly density in these areas. The number of patients shows a strong positive correlation (r=0.516, P<0.05) to the sand fly abundance with a lag of 7 months. Systematic surveillance of sand flies as a part of general healthcare services is strongly recommended to identify and prevent possible outbreaks through timely planned vector control measures.Item An investigation of a new cutaneous leishmaniasis endemic area in Western Sri Lanka(Oxford University Press, 2021) Mallawarachchi, C.H.; Chandrasena, N.; Wijerathna, T.; Dalpadado, R.; Mallawarachchi, M.S.M.N.S.; Gunarathna, D.G.A.M.; Gunathilaka, N.BACKGROUND: The aim was to investigate an emerging focus of cutaneous leishmaniasis (CL) in Gampaha district, Western Sri Lanka. METHODS: Sociodemographics of CL patients in Mirigama, Gampaha district, were compared with controls using a structured questionnaire. Clinical data and geographic positioning system coordinates of patients were recorded. Sandflies collections were performed in four selected sites using indoor hand collection (162 units) and cattle-baited net traps (n=3). RESULTS: Of 73 patients (mean age 43.6 y; SD 20), 58.9% were males. Lesions consisted of nodules (52.1%) and ulcers (47.9%). Single lesions were seen in 69.9% of patients, while 30.1% had multiple lesions. Except for one mucosal lesion, all the others were cutaneous. Treatment consisted of sodium stibogluconate and cryotherapy (46.6%), sodium stibogluconate (45.2%) or cryotherapy (8.2%). Multiple lesions were more likely to receive combination therapy (p=0.013). The majority of those employed (81.1%; 27/33) were engaged in outdoor work. Male gender, low education attainment and poor disease awareness were significant risk factors for CL (p<0.05). Four households reported multiple cases. Phlebotomus argentipes was detected in all cattle-baited net traps and 35.3% of indoor hand collection units. CONCLUSIONS: CL is emerging in Gamapha district with Mirigama as the epicentre. Case distribution indicates local transmission, with P. argentipes as the probable vector. KEYWORDS: Sri Lanka; cutaneous leishmaniasis; emerging infectious diseases.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.
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