Browsing by Author "de Silva, N."

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100 Years of Mass Deworming Programmes: A Policy Perspective From the World Bank's Disease Control Priorities Analyses
(London : Academic Press, 2018) Bundy, D.A.P.; Appleby, L.J.; Bradley, M.; Croke, K.; Hollingsworth, T.D.; Pullan, R.; Turner, H.C.; de Silva, N.
For more than 100 years, countries have used mass drug administration as a public health response to soil-transmitted helminth infection. The series of analyses published as Disease Control Priorities is the World Bank's vehicle for exploring the cost-effectiveness and value for money of public health interventions. The first edition was published in 1993 as a technical supplement to the World Bank's World Development Report Investing in Health where deworming was used as an illustrative example of value for money in treating diseases with relatively low morbidity but high prevalence. Over the second (2006) and now third (2017) editions deworming has been an increasingly persuasive example to use for this argument. The latest analyses recognize the negative impact of intestinal worm infection on human capital in poor communities and document a continuing decline in worm infection as a result of the combination of high levels of mass treatment and ongoing economic development trends in poor communities.
Acute Dermato-Lymphangio-Adenitis Following Administration of Infliximab for Crohn's Disease.
(American College of Gastroenterology, 2019) Liyanage, I.K.; Niriella, M.A.; de Silva, A.P.; de Silva, N.; de Silva, H.J.
Tumor necrosis factor-α inhibitor (TNF-α) is frequently used for Crohn's disease and other autoimmune conditions. Increased risk of infection is an accepted adverse effect of TNF-α, and routine screening for potential infections are carried out before initiation of therapy. We report the case of a patient who developed a localized painful swelling near the injection site, which was diagnosed as acute dermato-lymphangio-adenitis due to filarial infection. This adds to the limited number of case reports on parasitic complications following TNF-α therapy
Admission to medical schools in Sri Lanka: predictive validity of selection criteria
(Sri Lanka Medical Association, 2006) de Silva, N.R.; Pathmeswaran, A.; de Silva, N.; Edirisinghe, J.S.; Kumarasiri, P.V.R.; Parameswaran, S.V.; Seneviratne, R.; Warnasuriya, N.; de Silva, H.J.
OBJECTIVE: To assess the extent to which current selection criteria predict success in Sri Lanka's medical schools. METHODS: The study sample consisted of all students selected to all six medical schools in two consecutive entry cohorts. The aggregate marks of these students at the General Certificate of Education (GCE) Advanced Level examination, the district of entry, admission category, candidate type (school/private) and gender, were identified as entry point variables. Success in medical school was measured in four ways: the ability to pass the first summative examination and the final examination at the first attempt, and obtaining honours in either examination. Multivariate analysis using logistic regression was used to assess the extent to which these entry point factors predict variability in outcome measures.RESULTS: Aggregate scores among the 1740 students in the study sample ranged from 212 to 356, with a median of 285. The male:female ratio was 1.4:1. Private candidates (taking the examination for the third time) accounted for 22% of students. Being a school candidate, female and having a higher aggregate score, were the only independent predictors of success for all four outcome measures. The aggregate score alone accounted for only 1-7% of the variation in performance in medical school. CONCLUSIONS: Marks obtained at the A Level examination (the only academic criterion currently used for selection of medical students in SriLanka) is a poor predictor of success in medical school.
Analysis of elemental profiles in selected industrial effluents reaching Kelani River using inductively coupled plasma spectrometry
(Sri Lanka Association for the Advancement of Science, 2013) Pathiratne, K.A.S.; Pathiratne, A.; Hemachandra, C.K.; de Silva, N.
Anthelmintics: a review of their comparative clinical pharmacology
(Springer International, 1997) de Silva, N.; Guyatt, H.; Bundy, D.
Virtually all the important helminth infections in humans can be treated with one of 5 anthelmintics currently in use: albendazole, mebendazole, diethylcarbamazine, ivermectin and praziquantel. These drugs are vital not only for the treatment of individual infections, but also useful in controlling transmission of the more common infections. This article reviews briefly the pharmacology of these 5 drugs, and then discusses current issues in the use of anthelmintics in the treatment and/or control of soil-transmitted nematode infections, filariasis, onchocerciasis, schistosomiasis (and other trematode infections), neurocysticercosis and hydatidosis. Mebendazole and albendazole are most effective against intestinal nematodes, but are contraindicated during the first trimester of pregnancy. The efficacy of prolonged therapy with these 2 drugs for treatment of larval cestode infections has not yet been established. Diethylcarbamazine is widely used to treat and control lymphatic filariasis, but adverse effects related to death of microfilariae or damage to adult worms may be marked. While ivermectin has been used in the treatment of patients with onchocerciasis, it is also undergoing investigation against lymphatic filariae. Praziquantel, used to treat schistosome infections, is also effective in other trematode infections and adult cestode infections
Assessment of knowledge and perceptions on leishmaniasis: An island-wide study in Sri Lanka
(Public Library of Science, 2022) Dewasurendra, R.; Silva, H.; Samaranayake, N.; Manamperi, N.; de Silva, N.; Karunanayake, P.; Senarath, U.; Senanayake, S.; Zhou, G.; Karunaweera, N.
Cutaneous leishmaniasis (CL) is a notifiable disease in Sri Lanka with increasing case numbers reported from every part of the country. In addition to disease treatment and vector control measures, knowledge and perceptions in a community are key contributors to a successful intervention program. An island-wide survey was carried out to assess the knowledge and perceptions regarding CL across the island, with 252 confirmed CL cases and 2,608 controls. Data was collected by trained personnel, using a pre-tested Case Reporting Form (CRF). Although the percentage who referred to CL by its correct name was low (1.4%), majority stated that it is a fly induced skin disease (79.1%). Knowledge on the symptoms, curability and the name of the vector was high in these communities, but specific knowledge on vector breeding places, biting times and preventive methods were poor. The patients were more knowledgeable when compared to the controls. Differences in the level of knowledge could be identified according to the level of education of the participants as well as across the different areas of the country. The main source of information was through the healthcare system, but the involvement of media in educating the communities on the disease was minimal. While this study population was unaccustomed to the use of repellants or sprays, the use of bed nets was high (77.7% of the participants) in this study population. Although misconceptions and incorrect practices are rare in Sri Lankan communities, promoting health education programs which may improve disease awareness and knowledge on vector and its control will further strengthen the control and prevention strategies.
Clinical use of anthelmintics
(1997) de Silva, N.; Guyatt, H.; Bundy, D.
Cochrane Reviews on deworming and the right to a healthy, worm-free life
(Public Library of Science, 2015) de Silva, N.; Ahmed, B.N.; Casapia, M.; de Silva, H.J.; Gyapong, J.; Malecela, M.; Pathmeswaran, A.
Constructive Relativism
(University of Kelaniya, 2005) de Silva, N.
In this paper a new philosophical approach is presented, that could be termed Paticcasamuppadin that is different from the conventional materialistic and idealistic approaches. The materialists starting with the Greeks in the west, and the Dravyavadins in Bharat, in general attempted to reduce all phenomena to a materialist base. The Buddhist idealists in the form of Vinnanavadins and the Greek idealists on the other hand wanted to show that the mind is supreme, and that the so-called material world was the creation of the mind. We present a different approach, where the world as an observer ‘sees’ is created by the observer due to avidya of anicca, dukka and anatta which could be ‘roughly translated’ as ignorance of impermanence and soullessness. The ‘world’ is anicca, dukka, anatma and sunya. However, anicca and anatta are not concepts, and as such it is futile to attempt to translate them into English or any other language. Even in Pali they should be considered as non-concepts that defy explanation using concepts or other words. Also, unlike in Madhyamikavada sunya is not elevated to a concept with sunyata coming into the picture as a noun. We argue that the world is nothing but the creation of the observer, and the world is same as the knowledge of the world. In the present approach it is not assumed that a world exits independent of the observer who attempts to know or gather ‘information’ of an already existing world. The observer creates knowledge of the world, and hence the world exists relative to the sense organs, mind and the culture of the observer. The knowledge is thus created by the mind with the aid of the other sense organs. There is no knowledge or world, before such knowledge of the world is created, and the knowledge is created as concepts, theories, etc., by the observer. Thus, the so-called world is the conceptual and theoretical world of the observer that has been created in the mind. It should be noted that the concepts need not be in the form of words, as images formed in the mind are also considered as concepts. However, according to the approach presented in the paper the mind is not an absolute that has an independent existence. A ‘model’ is created in which the mind of an observer is also created by the mind itself! The mind is presented as a stream of ‘cittas’ which themselves are the concepts that could be supposed to exist in the smallest duration that can be created (grasped) by the mind. The logic of the present approach is cyclic and fourfold, and not Aristotelian.
The Costs and cost-cffectiveness of mass treatment for intestinal nematode worm infections using different treatment thresholds
(Public Library of Science, 2009) Hall, A.; Horton, S.; de Silva, N.
BACKGROUND: It is estimated that almost a half of all of people living in developing countries today are infected with roundworms, hookworms, or whip worms or combinations of these types of intestinal nematode worms. They can all be treated using safe, effective, and inexpensive single-dose generic drugs costing as little as USD 0.03 per person treated when bought in bulk. The disease caused by intestinal nematodes is strongly related to the number of worms in the gut, and it is typical to find that worms tend to be aggregated or clumped in their distribution so that <20% of people may harbour >80% of all worms. This clumping of worms is greatest when the prevalence is low. When the prevalence rises above 50%, the mean worm burden increases exponentially, worms are less clumped, and more people are likely to have moderate to heavy infections and may be diseased. Children are most at risk. For these reasons, the World Health Organization (WHO) currently recommends mass treatment of children > or =1 year old without prior diagnosis when the prevalence is > or =20% and treatment twice a year when the prevalence is > or =50%. METHODS AND FINDINGS: The risk of moderate to heavy infections with intestinal nematodes was estimated by applying the negative binomial probability distribution, then the drug cost of treating diseased individuals was calculated based on different threshold numbers of worms. Based on this cost analysis, a new three-tier treatment regime is proposed: if the combined prevalence is >40%, treat all children once a year; >60% treat twice a year; and >80% treat three times a year. Using average data on drug and delivery costs of USD 0.15 to treat a school-age child and USD 0.25 to treat a pre-school child (with provisos) the cost of treating children aged 2-14 years was calculated for 105 low- and low-middle-income countries and for constituent regions of India and China based on estimates of the combined prevalence of intestinal nematode worms therein. The annual cost of the three-tier threshold was estimated to be USD 224 million compared with USD 276 million when the current WHO recommendations for mass treatment were applied. CONCLUSION: The three-tier treatment thresholds were less expensive and more effective as they allocated a greater proportion of expenditures to treating infected individuals when compared with the WHO thresholds (73% compared with 61%) and treated a larger proportion of individuals with moderate to heavy worm burdens, arbitrarily defined as more than 10 worms per person (31% compared with 21%).
A digital library for ola leave books
(University of Kelaniya, 2008) de Silva, N.; Adikari, G.; Piyadasa, J.D.A.I.; Dharmarathna, G.P.G.
Effect of mebendazole threapy in pregnancy on birth outcome
(Sri Lanka Medical Association, 1998) de Silva, N.; Sirisena, J.; Gunasekera, D.; de Silva, J.
OBJECTIVES : A prospective, unmatched, case-control study was done to assess the safety of mebendazole threapy in pregnancy, a hitherto uninvestigated factor. DESIGN : All women delivering in the University Obstetrics Unit of the Ragama Teaching Hospital between May 1996 and, March 1997 were administered a questionnaire soon after delivery. Details of the birth and the baby were recorded; suspected defects were confirmed by a paediatrician. The incidence of congenital defects in babies of mothers who had taken mebendazole during the pregnancy was compared with the incidence among those who had not taken an anthelmintic (controls). Data analysis was done using Epi Info 6.03. RESULTS : Of 3688 women, 73.5% had taken mebendazole, 24.8% had not taken any any anthelmintic , 1.1% had taken an anthelmintic but could not identify it and 0.6% had taken pyrantel or albedazole. The incidence of birth defects was 2.36% {64/2711) in the mebendazole group compared with 2.3% (21/913) in the controls (odds ratio 1.03, 95% confidence limits 0.61 - 1.75). This difference was not statistically significant even when corrected for other known risk factors by stratified analysis . Data regarding timing of mebendazole threapy was available for 2660 women; 6.9% in the first trimester, 83.8% in the second, and 9.2% in the third. The incidence of birth defects among women who had taken mebendazole in the first trimester was 3.24% (6/185). giving an odds ratio of 1.42 against the controls; this was also not statistically significant.CONCLUSIONS : The use of mebendazole in pregnancy does not lead to a significant increase in the risk of congenital defects.
Evaluation of rapid extraction and isothermal amplification techniques for the detection of Leishmania donovani DNA from skin lesions of suspected cases at the point of need in Sri Lanka
(BioMed Central, 2018) Gunaratna, G.; Manamperi, A.; Bohiken-Fascher, S.; Wickremasinghe, R.; Gunawardena, K.; Yapa, B.; Pathiana, N.; Pathirana, H.; de Silva, N.; Sooriyaarachchi, M.; Deerasinghe, T.; Mondal, D.; Ranasinghe, S.; Abd EI Wahed, A.
BACKGROUND: Leishmaniasis is a disease caused by vector-borne protozoans. In Sri Lanka, the cutaneous form of the disease is predominant, which is usually diagnosed using Giemsa-stained slit skin smear examination and by histology. However, the sensitivity of slit skin smears and histology are reportedly low. Moreover, facilities for the highly sensitive polymerase chain reaction (PCR) are available only in a few highly-equipped parasitology laboratories. Therefore, there is a need for low cost, sensitive and specific screening tests for diagnosis of leishmaniasis at the point of need. RESULTS: In this study, a mobile suitcase laboratory applying novel extraction (SpeedXtract) and isothermal amplification and detection (recombinase polymerase amplification assay, RPA) methods were evaluated for the diagnosis of cutaneous leishmaniasis in Sri Lanka. First, the developed assay was applied to three different sample types (punch biopsy, slit skin smears and fine needle aspirates) at a local hospital. The results showed that the 2 mm punch biopsy sample produced the best exponential amplification curve and early fluorescence signal in the RPA assay. Secondly, punch biopsies were collected from 150 suspected cutaneous leishmaniasis cases and screened with SpeedXtract/RPA, RNAlater/PCR and ATL buffer/PCR, in addition to Giemsa-stained slit skin smears. Fifty-seven samples were negative in all detection methods. In total 93 samples were positive with assay sensitivities of 65.5% (SpeedXtract/RPA), 63.4% (RNAlater/PCR) and 92.4% (ATL buffer/PCR). The Giemsa-stained slit skin smear delivered the worst clinical sensitivity (32.2%). CONCLUSIONS: The SpeedXtract/RPA method under field conditions took 35 min, while almost 8 h were needed to finalize the extraction and detection by PCR in the laboratory. The SpeedXtract/RPA method produced similar sensitivity to samples preserved in RNAlater and subjected to PCR amplification, but both were less sensitive than ATL-preserved samples subjected to PCR amplification. There is a need for a standardization of sample collection and nucleic acid extraction methods.
An experiment on interference
(Research Symposium 2009 - Faculty of Graduate Studies, University of Kelaniya, 2009) Chandana, A.W.S.; Siripala, W.; de Silva, N.
Experiments on interference
(University of Kelaniya, 2008) Chandana, A.W.S.; Siripala, W.P.; de Silva, N.
We report a few experiments carried out to demonstrate the formation of interference patterns with thin Aluminium sheets placed along zero probability positions (positions where the probability of finding a particle is zero). The presence of the Aluminium sheets did not destroy the interference patterns though one would have expected the particles to interact with the sheets and wash out the patterns. In the experiment arrangement, Laser beam (He/Ne gas laser, wave length 633nm, maximum power <1mW ), a double-Slit (a= O.lmm, b = 1mm), digital camera, Aluminium sheets (0.056cm x 3cm x 40cm), two lenses and traveling microscope were needed. Eight thin Aluminium sheets of dimensions 0.56cm x 3cm x 30cm were placed along zero probability positions within the central maxima of interference pattern, and 20 more thin small Aluminium sheets of dimension 0.056cm x 3cm x 6cm were paced along zero probability positions of the diffraction pattern. The interference patterns were not changed as can be seen in the figure 1 Now the front edge of the first Aluminium sheet from the left of the eight sheets that were placed within the central maxima was moved through 4mm without moving the rear end of the sheet. The diffraction and interference patterns were washed off as shown in the figure 2.
A general relativistic solution for the space time generated by a spherical shell with constant uniform density
(University of Kelaniya, 2008) Wimaladharma, N.A.S.N.; de Silva, N.
In this paper we present a general relativistic solution for the space time generated by a spherical shell of uniform density. The Einstein's field equations are solved for a distribution of matter in the form of a spherical shell with inner radius a and outer radius b and with uniform constant density p . We first consider the region which contains matter (a < r < b ). As the metric has to be spherically symmetric we take the metric in the form ds2 =ev c2dt2 -eA.dr2 -r2d0.2, where d0.2 = (dB2 +sin2B drjJ2 ), A and v are functions of r as in Adler, Bazin and Schiffer1 where the space time metric for a spherically symmetric distribution of matter in the form of sphere of uniform density has been worked out. Solving the field equations, we o btain eA. = 1 ( r2 1 EJ --+ R2 -r and 2 Here R 2 = �� , where c and K are the velocity of the light and the gravitational 87rKp constant respectively and A , B and E are constants to be determined. Let the metric for the matter free regions be ds2 =ev c2dt2 -eA.dr2 -r2d0.2, where as before from spherical symmetry A and v are functions of r . Solving the field equations, we o btain, e" and e'' in the form e' �� (I : 7) and e" �� n(l + ��), for the regions 0 < r b. where D and G are constants. For the region 0 < r b, the metric should be Lorentzian at in finity. So D = 1. Hence the metric for the exterior matter free region is ds' = ( 1 + ��}'dt'- (I +l��r 2 -r2dn2 • Then we can write the metric for the space-time as ds2 = D c2 dt2 - dr2 -r2dQ2 , whenO < r b. - !! - - (b3 - a3) E- 2 G R - R 2 ' (i ) __ (ii) 157 where r 2(a3 - r3 + rR2 Y ( - 9a 6 J;- 3a3rYz R2 + 2rh R 4 ) f Yz dr = --------,-- Yz.,--------'------------'----- (1 - C + _a_3 -) 2 r% ( a3 - r3 + rR2 ) 2 (-27a9 + 27a6r3 - 2 7a6rR2 + 4a3 R6 - 4r3 R6 + 4rR6) R2 R2 r rR2 tP -J; a3 + r3 (-I + :: ) ] F(f/Jim)= fV - msin2 e) dB tP ( )Yz ff ff and E(f/J I m)= f 1 -m sin 2 e dB , -- < fjJ <- 0 2 2 0 are the Elliptic integrals of first kind and second kind respectively, where fjJ =Arcsin (- ;+r3) (r3 - r2) and Here r1 =The first root of ( - 1 + R2 r2 + a3r3 )r2 =The second root of ( - 1+R2 r2 +a3r3. ). r3 =The third root of ( - 1+R2 r2 +a3r3). Furthermore we know that the potential fjJ of a shell of inner radius a1 and outer radius b1 and constant uniform density in Newtonian gravitation is given by fjJ = 2ffKp(a12 -b12) ,;. 2ffKp 2 4ffKp 3 2 b 2 'f'=-3-r +�� a1 - ffKP 1 fjJ = _ 4ffKp (a13 - b13) Using the fact that g00 = ( 1 + ��). (for example in Adler, Bazin and Schiffer1 )we find that the constants a,, b1 in Newtonian gravitation and D can be written in the form __ (iii) __ (iv) D =(I+ 3(a�;,b/ l} Hence the final form of the metric is O
The Global burden of snakebite: a literature analysis and modelling based on regional estimates of envenoming and deaths
(Public Library of Science, 2008) Kasturiratne, A.; Wickremasinghe, A.R.; de Silva, N.; Gunawardena, N.K.; Pathmeswaran, A.; Premaratna, R.; Savioli, L.; Lalloo, D.G.; de Silva, H.J.
BACKGROUND: Envenoming resulting from snakebites is an important public health problem in many tropical and subtropical countries. Few attempts have been made to quantify the burden, and recent estimates all suffer from the lack of an objective and reproducible methodology. In an attempt to provide an accurate, up-to-date estimate of the scale of the global problem, we developed a new method to estimate the disease burdendue to snakebites. METHODS AND FINDINGS: The global estimates were based on regional estimates that were, in turn, derived from data available for countries within a defined region. Three main strategies were used to obtain primary data: electronic searching for publications on snakebite, extraction of relevant country-specific mortality data from databases maintained by United Nations organizations, and identification of grey literature by discussion with key informants. Countries were grouped into 21 distinct geographic regions that are as epidemiologically homogenous as possible, in line with the GlobalBurden of Disease 2005 study (Global Burden Project of the World Bank). Incidence rates for envenoming were extracted from publications and used to estimate the number of envenomings for individual countries; if no data were available for a particular country, the lowest incidence rate within a neighbouring country was used. Where death registration data were reliable, reported deaths from snakebite were used; in other countries, deathswere estimated on the basis of observed mortality rates and the at-risk population. We estimate that, globally, at least 421,000 envenomings and 20,000 deaths occur each year due to snakebite. These figures may be as high as 1,841,000 envenomings and 94,000 deaths. Based on the fact thatenvenoming occurs in about one in every four snakebites, between 1.2 million and 5.5 million snakebites could occur annually. CONCLUSIONS: Snakebites cause considerable morbidity and mortality worldwide. The highest burden exists in South Asia, Southeast Asia, and sub-Saharan Africa. Comment in Estimating the global burden of snakebite can help to improve management. [PLoS Med. 2008]
Helminth infections: soil-transmitted helminth infections and schistosomiasis
(Oxford University Press and World Bank, 2006) Hotez, P. J.; Bundy, D.A.P.; Beegle, K.; Brooker, S.; Drake, L.; de Silva, N.; Montresor, A.; Engels, D.; Jukes, M.; Chitsulo, L.; Chow, J.; Laxminarayan, R.; Michaud, C. M.; Bethony, J.; Correa-Oliviera, R.; Xiao Shu-Hua; Fenwick, A.; Savioli, L.
Human resources for health in Sri Lanka over the post-independence period: key issues
(Sri Lanka Medical Association, 2023) de Silva, D.; Chandratilake, M.; de Silva, N.
No abstract available
Intestinal Nematodes: Ascariasis
(Saunders-Elsevier, 2012) Bundy, D.A.P.; de Silva, N.; Brooker, S.