Browsing by Author "Wijerathna, T."

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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.
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.
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.
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.
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.
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.
The Economic Impact of Cutaneous Leishmaniasis in Sri Lanka.
(Hindawi Publishers, 2018) Wijerathna, T.; Gunathilaka, N.; Gunawardena, K.
Cutaneous leishmaniasis (CL) is a neglected tropical disease which affects mainly the poorest communities in developing countries. Considering the limited published information on economic impact of CL in Sri Lanka, the current study was conducted with the objective of revealing the nature and magnitude of the economic impact of CL in three selected disease endemic regions in Kurunegala District, Sri Lanka. The patient records of CL notified of relevant Medical Officer of Health (MOH) office during 2013- 2016 were obtained. Patient households were visited and data collection was done using an interviewed administered questionnaire. The majority of patients (57%) were economically active at the time of infection. Of them, 65% were the only contributors to household economy. Total median costs including both direct and indirect costs were 66.85 USD (Rs. 10,831) (IQR = 57.26 - 86.78 USD), while total median economic loss to households was 61.27 USD (Rs. 9,927) (IQR= 49.61- 75.04 USD). From provider perspective, total median cost per patient was 22.83 USD (Rs. 3,696). The mean total economic loss was denoted as 65.26 USD (Rs. 10,572) which is about 5.4% of the annual household income and 20.9% of the mean annual per capita income of the study population. Although economic impact of CL infection is not catastrophic according to current interpretation, the infection may have significant economic impacts on households when considering the mean economic loss to household as a percentage of the mean annual per capita income of the population.
Entomological and epidemiological investigations in a newly established focus of cutaneous leishmaniasis in Kegalle district, Sri Lanka
(Faculty of Graduate Studies, University of Kelaniya Sri Lanka, 2022) Wickramasinghe, K.; Wijerathna, T.; Gunathilaka, N.; Perera, A.; Bandara, S.
Leishmaniasis is a protozoan infection transmitted by phlebotomine sand flies. The published information on the vector distribution, abundance and potential risk factors that are favorable for disease transmission in Kegalle district are not available. Hence, understanding the trends in disease establishment, epidemiological characteristics, and the bioclimatic suitability of the area for disease prediction. The total number of leishmaniasis patients notified in Kegalle district and Sri Lanka from 2016-2020 was obtained from the Epidemiology Unit, Sri Lanka. Rambukkana and Warakapola Medical Officer of Health (MOH) areas that have reported the highest numbers of cases from 2016 – 2018 in Kegalle district were selected as the study sites in the current study. Patients were visited and socio-economic, demographic, environmental and awareness-related information was collected using an interviewer-administered questionnaire. A randomly selected household with no records of CL in the same locality of the patient household was included as the control group to match the case group at a 1:1 ratio. Entomological surveys were conducted from July 2019- July 2020 using standard entomological techniques. Bioclimatic suitability was evaluated using ecological niche modeling (ENM). A total of 107 patients were reported from Rabukkana and Warakapola MOH areas from 2016-2020. Of them 88 were traced and included in the study. The risk factors were assessed using the chi squared test at 95% confidence intervals. Age was divided into ten-year age groups for analysis. The findings indicate that leishmaniasis in the Kegalle district progressed to the outbreak level within 3 years since the first recorded case in 2016. School students (n=22, 25%, P<0.05) and individuals between 11-20 years of age (n = 33, 37.5%, P<0.05) were identified as the main risk groups. The presence of composting sites (n=65, 73.9%, P<0.05) that provide potential breeding grounds for sand flies, abandoned lands (n=63, 71.6%, P<0.05) which are potential diurnal resting sites of adult sand flies, and suboptimal (dark or normal) lighting conditions (n=87, 98.8%, P<0.05) in the house that may facilitate vector activity were denoted as significant risk factors for leishmaniasis occurrence compared the control group. The level of awareness of the disease was poor in both the test and control groups. Ecological niche modeling revealed that the areas closer to the Kurunegala district, a predominant leishmaniasis endemic district in the intermediate zone, have high bioclimatic suitability for leishmaniasis. The sand flies including, P. argentipes (n=121, 42%) and S. zeylanica (n=164, 56.9%) were present in high densities in this area. Hence, the control efforts focused on raising awareness, while implementing vector control and effective case management, prioritizing the high-risk areas is vital.
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.
Establishment of a colony of Phlebotomus argentipes under laboratory conditions and morphometric variation between wild-caught and laboratory-reared populations.
(Hindawi Pub. Corp., 2020) Wijerathna, T.; Gunathilaka, N.; Gunawardena, K.
ABSTRACT:The field-based studies on sand flies are not adequate to uncover information required for the control of the leishmaniasis through reduction of vector populations. Therefore, establishment and maintenance of laboratory colonies of sand flies is an essential step in leishmaniasis research. In the current study, a colony of P. argentipes was established from wild-caught sand flies following standard procedures from the published literature. Morphological measurements of laboratory-reared and wild-caught individual sand flies were compared to assess the difference between two groups. The colony was successfully established under confined laboratory conditions. The comparison of morphometric parameters revealed that the laboratory-reared sand flies are significantly larger than those caught from wild, suggesting a possibility of increased fitness of sand flies under favorable environmental conditions which may cause higher prevalence in the disease. The current study reports the first successful attempt in colonizing sand flies under laboratory conditions. However, the colony data suggest that the conditions extracted from the published literature need to be optimized to suit local settings in order to achieve maximum population sizes within the available amount of resources.
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.
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.
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.
Kidney damage biomarkers detect acute kidney injury but only functional markers predict mortality after paraquat ingestion
(Amsterdam, Elsevier/North Holland, 2015) Mohamed, F.; Buckley, N.A.; Jayamanne, S.; Pickering, J.W.; Peake, P.; Palangasinghe, C.; Wijerathna, T.; Ratnayake, I.; Shihana, F.; Endre, Z.H.
Acute kidney injury (AKI) is common following paraquat ingestion. The diagnostic performance of injury biomarkers was investigated in serial blood and urine samples from patients from 5 Sri Lankan hospitals. Functional AKI was diagnosed using serum creatinine (sCr) or serum cystatin C (sCysC). The 95th centile in healthy subjects defined the urinary biomarker cutoffs for diagnosing structural AKI. 50 poisoned patients provided 2 or more specimens, 76% developed functional AKI [AKIN stage 1 (n=12), 2 (n=7) or 3 (n=19)]; 19/26 patients with AKIN stage 2/3 also had functional AKI by sCysC criteria (≥50% increase). Urinary cystatin C (uCysC), clusterin (uClu) and NGAL (uNGAL) increased within 24h of ingestion compared with NoAKI patients and healthy controls. Each biomarker demonstrated moderate diagnostic utility [AUC-ROC: uCysC 0.79, uNGAL 0.79, uClu 0.68] for diagnosis of functional AKI at 16h. Death occurred only in subjects with functional AKI. Structural biomarker-based definitions detected more AKI than did sCr or sCysC, but did not independently predict death. Renal injury biomarkers did not add clinical value to patients who died rapidly due to multi-organ failure. Use of injury biomarkers within 16-24h may guide early intervention for reno-protection in less severe paraquat poisoning.
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.
Phlebotomine sand flies (Psychodidae: Diptera) of Sri Lanka: a review on diversity, biology and bionomics
(Magnolia Press, Auckland, New Zealand, 2019) Wijerathna, T.; Gunathilaka, N.
Phlebotomine sand flies are medically important insects widespread throughout the world and responsible for the transmission of several diseases to humans and other animals including leishmaniasis and sand fly fever. In Sri Lanka, a total of 22 species of sand flies belonging to two genera, namely: Phlebotomus and Sergentomyia, have been recorded with 6 and 16 species, respectively. The current study reports a complete list of the species of sand flies reported from Sri Lanka with a review on global and local distribution, biology and bionomics of each species as per published literature up to June 2018.
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.
Potential challenges of controlling Leishmaniasis in Sri Lanka at a disease outbreak
(Hindawi Pub. Co., 2017) Wijerathna, T.; Gunathilaka, N.; Gunawardena, K.; Rodrigo, W.
The present works reviewed the existing information on leishmaniasis in Sri Lanka and in other countries, focusing on challenges of controlling leishmaniasis in the country, in an outbreak. Evidence from recent studies suggests that there is a possibility of a leishmaniasis outbreak in Sri Lanka in the near future. Difficulty of early diagnosis due to lack of awareness and unavailability or inadequacy of sensitive tests are two of the main challenges for effective case management. Furthermore, the absence of a proper drug for treatment and lack of knowledge about vector biology, distribution, taxonomy and bionomics, and reservoir hosts make the problem serious. The evident potential for visceralization in the cutaneous variant of L. donovani in Sri Lanka may also complicate the issue. Lack of knowledge among local communities also reduces the effectiveness of vector and reservoir host control programs. Immediate actions need to be taken in order to increase scientific knowledge about the disease and a higher effectiveness of the patient management and control programs must be achieved through increased awareness about the disease among general public and active participation of local community in control activities.
Presence of leishmaniasis causing agent, Leishmania donovani, in biting midges (Culicoides sp) at a disease endemic area of Sri Lanka: Could it be a probable vector?
(Faculty of Graduate Studies, University of Kelaniya Sri Lanka, 2022) Wijerathna, T.; Wimalasiri, U.; Wijegunawardena, A.; Gunathilaka, N.; Rodrigo, W. W. P.
Biting midges are a group of dipteran insects of the family Ceratopogonidae. Some species of biting midges are known to be vectors for filaria parasites that infect humans, and some are known to be vectors of viruses that infect livestock. Evidence suggests that biting midges may be a potential vector for Leishmania parasites in other countries. Biting midges are found in high densities in leishmaniasis endemic regions of Sri Lanka. This high density and biting nuisance suggest that these insects may have a possible role as secondary vectors (if not primary vectors) for leishmaniasis in these areas. The first criterion of leishmaniasis vector incrimination is the detection of parasites from the suspected vectors. Therefore, the present study examined the Leishmania donovani parasites circulate within biting midge populations at a leishmaniasis endemic area in Sri Lanka. The study was conducted in Medawachchiya Medical Officer of Health area in Anuradhapura District, Sri Lanka. Biting midges were collected using cattle baited net traps during December 2021. The collected specimens were identified using morphological identification keys. The specimens were surface sterilized using 70% ethanol and the DNA was extracted from the fly using MightyPrep reagent for DNA (Takara, Japan). The parasite DNA was detected using a Polymerase Chain Reaction (PCR) using Leishmania donovani specific primers that target kinetoplast minicircle gene. The amplicons were visualized under UV light after running on a 2% agarose gel stained with ethidium bromide. A total of 42 biting midges were collected and all of them were females. The collection consisted of a single species similar to Culicoides imicola in morphology. The gel electrophoresis and subsequent UV visualization indicated that two of the samples were positive for L. donovani DNA indicating a parasite circulation rate of 4.76% within the wild biting midge population. The results of the current study suggest that the L. donovani, the main causative agent of leishmaniasis in Sri Lanka, circulates within biting midge populations indicating a possibility of this species being a vector for leishmaniasis in Sri Lanka. According to the World Health Organization (WHO) criteria for leishmaniasis vector incrimination, the detection of the parasites within the insect is the first step. Further studies to assess the luxuriant growth of the parasite within midge midgut and experimental transmission using animal models are needed to confirm the vector status. Considering the medical and veterinary importance, the studies on biting midges of Sri Lanka are recommended.