Browsing by Author "Isbister, G."

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Community incidence of snakebite and envenoming in Sri Lanka; results of a national survey
(Sri Lanka Medical Association, 2014) Pathmeswaran, A.; Kasturiratne, A.; Gunawardena, N.K.; Wijayawickrama, B.A.; Jayamanne, S.F.; Ediriweera, D.S.; Isbister, G.; Dawson, A.; Lalloo, D.G.; de Silva, H.J.
INTRODUCTION AND OBJECTIVES: We undertook the first ever country-wide community-based survey to determine the incidence of snakebite in Sri Lanka. METHODS: Data were collected through household interviews by trained data collectors.125 clusters were allocated to each of the 9 provinces of the country. Within each province the clusters were divided among the districts in proportion to their population. A Grama Niladhari (GN) division was defined as a cluster for data collection. The clusters were selected using simple random sampling, and in each cluster 40 households were sampled consecutively from a random starting point. RESULTS: Data relating to 165,665 individuals (0.8% of the population of Sri Lanka) living in 44,136 households in 1,118 clusters was collected from June 2012 to May 2013. 695 (males 418) snakebites and 323 (males!93) significant envenomings (local tissue necrosis or systemic envenoming) were reported during the 12 months preceding the interview. The overall community incidence of snakebites and significant envenoming were 398 and 151 per 100,000 population, respectively. 446 (64.2%) bites and 208 (64.4%) envenomings were in people aged 30 to 59 years. There was wide variation between districts, the worst affected being Mullaitivu, Anuradhapura, Batticaloa, and Poionnaruwa, ali in the dry zone, mainly agricultural areas of the country. CONCLUSIONS: Sri Lanka has a high community incidence of snakebite and envenoming with a marked geographical variation.This variation underlines both the inaccuracy of extrapolating data of localised surveys to national or regional levels and the need to prioritise distribution of resources for treatment of snakebite even in small countries.
Community incidence of snakebite in the Amiradhapura district
(Sri Lanka Medical Association, 2013) Kasturiratne, A.; Gunawardena, N.K.; Wijayawickrama, B.A.; Jayamanne, S.F.; Pathmeswaran, A.; Isbister, G.; Dawson, A.; de Silva, H.J.
INTRODUCTION AND OBJECTIVES: The community incidence of snakebite in Sri Lanka is unknown. To investigate incidence of snakebite, we undertook a community study in the Anuradhapura district as part of an ongoing countrywide survey on snakebite. METHODS: The survey was designed to sample at least 1% of the population in each district Within the district, a Grama Niladhari (GN) division, was defined as a cluster for data collection. The number of clusters required to sample at least 1 % of the population was first determined, and clusters were then selected using simple random sampling. In each selected cluster 40 households were sampled consecutively from a random starting point. Population estimates of snakebite were constructed for the district. RESULTS: The Anuradhapura district has a total of 694 GN divisions, and 84 were surveyed. This included 3357 households and a population of 13,428 (1.6% of the district's population). Eightysix snakebites were reported within the last 12 months. Extrapolating this to the district (mid-year population=855,373), the estimated snakebites in Anuradhapura district was 5478. The crude community incidence of snakebite in the Anuradhapura district was 640.5 per 100, 000 population. CONCLUSIONS: The incidence of snakebite in the community is high in the Anuradhapura district, with one in 156 persons bitten annually.
Envenoming Snakebite Risk Map for Sri Lanka
(Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2016) Ediriweera, D.; Kasturiratne, A.; Pathmeswaran, A.; Pathmeswaran, A.; Gunawardena, N.; Jayamanne, S.; Wijayawickrama, B.; Isbister, G.; Giorgi, A.D.E.; Diggle, P.; Lalloo, D.; de Silva, J.
Snakebite is a neglected tropical disease. Hospital based statistics often underestimate snakebite incidence because a significant proportion of victims seek traditional treatments. Since geospatial risk assessments of snakebite envenoming are rare, health care resources are distributed based on administrative boundaries rather than on a need analysis. The aim of the study was to develop a snakebite envenoming risk map for Sri Lanka. Epidemiological data was obtained from a community-based island-wide survey. The sample was distributed equally among the nine provinces. 165,665 participants living in 1118 Grama Niladhari divisions were surveyed. Model-based geostatistics was used to determine the geographical distribution of envenoming bite incidence. The Monte Carlo maximum likelihood method was used to obtain parameter estimates and plug-in spatial predictions of risk. A predictive model was developed with natural and social environmental variables to construct an estimated envenoming bite incidence map and a probability contour map (PCM) to demonstrate the spatial variation in the predictive probability that local incidence does or does not exceed national envenoming snakebite incidence (i.e. 151 per 100,000). Envenoming bite incidence had a positive association with elevation up to 195 meters above sea level, with incidence dropping at higher elevations. The incidence of envenoming was higher in the dry zone compared to intermediate and wet climatic zones and decreased with increasing population density. Developed risk maps showed substantial within-country spatial variation in envenoming bites. Conclusion: The risk maps provide useful information for healthcare decision makers to allocate resources to manage snakebite envenoming in Sri Lanka. We used replicable methods which can be adapted to other geographic regions after re-estimating spatial covariance parameters for each region of interest.
Evaluating spatiotemporal dynamics of snakebite in Sri Lanka: Monthly incidence mapping from a national representative survey sample
(Public Library of Science, 2021) Ediriweera, D.S.; Kasturiratne, A.; Pathmeswaran, A.; Gunawardena, N.K.; Jayamanne, S.F.; Murray, K.; Iwamura, T.; Isbister, G.; Dawson, A.; Lalloo, D.G.; de Silva, H.J.; Diggle, P.J.
BACKGROUND: Snakebite incidence shows both spatial and temporal variation. However, no study has evaluated spatiotemporal patterns of snakebites across a country or region in detail. We used a nationally representative population sample to evaluate spatiotemporal patterns of snakebite in Sri Lanka. METHODOLOGY: We conducted a community-based cross-sectional survey representing all nine provinces of Sri Lanka. We interviewed 165 665 people (0.8% of the national population), and snakebite events reported by the respondents were recorded. Sri Lanka is an agricultural country; its central, southern and western parts receive rain mainly from Southwest monsoon (May to September) and northern and eastern parts receive rain mainly from Northeast monsoon (November to February). We developed spatiotemporal models using multivariate Poisson process modelling to explain monthly snakebite and envenoming incidences in the country. These models were developed at the provincial level to explain local spatiotemporal patterns. PRINCIPAL FINDINGS: Snakebites and envenomings showed clear spatiotemporal patterns. Snakebite hotspots were found in North-Central, North-West, South-West and Eastern Sri Lanka. They exhibited biannual seasonal patterns except in South-Western inlands, which showed triannual seasonality. Envenoming hotspots were confined to North-Central, East and South-West parts of the country. Hotspots in North-Central regions showed triannual seasonal patterns and South-West regions had annual patterns. Hotspots remained persistent throughout the year in Eastern regions. The overall monthly snakebite and envenoming incidences in Sri Lanka were 39 (95%CI: 38-40) and 19 (95%CI: 13-30) per 100 000, respectively, translating into 110 000 (95%CI: 107 500-112 500) snakebites and 45 000 (95%CI: 32 000-73 000) envenomings in a calendar year. CONCLUSIONS/SIGNIFICANCE: This study provides information on community-based monthly incidence of snakebites and envenomings over the whole country. Thus, it provides useful insights into healthcare decision-making, such as, prioritizing locations to establish specialized centres for snakebite management and allocating resources based on risk assessments which take into account both location and season.
Health seeking behavior of snakebite victims in Sri Lanka: findings from an island-wide community-based study
(Sri Lanka Medical Association, 2014) Kasturiratne, A.; Pathmeswaran, A.; Gunawardena, N.K.; Ediriweera, E.P.D.S.; Wijayawickrama, B.A.; Jayamanne, S.F.; Isbister, G.; Dawson, A.; Lalloo, D.G.; de Silva, H.J.
INTRODUCTION AND OBJECTIVES: Health seeking behaviour of snakebite victims in the community has rarely been described and we investigated this as part of a community-based island-wide study on snakebite in Sri Lanka. METHODS: The national snakebite study was conducted in a!! 25 districts, in SriJ_anka in 2012/2013. 44,136 households were sampled in randomly selected clusters. In these households, any member reported to have experienced a snake bite within the preceding 12 months was considered a case. Data related to the health seeking behavior of snakebite were obtained using an interviewer-administered questionnaire. RESULTS: Among 165,665 individuals surveyed, 695 (60% males; median age 43 years) snakebite victims were identified. 323 (46.5%) had evidence of envenoming. 682 (98.2%) had sought health services after the bite. 381 (54.8%) sought allopathic medicine and 99.7% of them obtained this service from the state health sector, while 43.3% sought alternative medicine. The lowest rates of seeking allopathic medicine were seen in the Kalutara (8.7%) and Kegalie (10.7%) districts while highest rates were seen in the districts Mannar, Mullativu and Kilinochchi (100%). Puttalam (92.9%), Vavuniya (92.3%},) Ampara (89.5%), Jaffna (88.9%) and Anuradhapura (86.0%) also had high rates. 70.1% of the victims with envenoming sought allopathic medicine. Victims who had envenoming were significantly more likely to seek allopathic medicine (OR=3.35; 95% confidence interval 2.44-4.59) than those without envenoming. CONCLUSIONS: A considerable proportion of snake bite victims still seek alternative medicines in Sri Lanka.'A wide variation of practices exists across the country. Victims with envenoming are more likely to seek allopathic medicine.