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Authors: Nadira D. Karunaweera, Sanath Senanayake, Samitha Ginige, Hermali Silva, Nuwani Manamperi, Nilakshi Samaranayake, Rajika Dewasurendra, Panduka Karunanayake, Deepa Gamage, Nissanka de Silva, Upul Senarath, Guofa Zhou

Journal: PLoS Negl Trop Dis

Leishmaniasis is on the rise in Sri Lanka in contrast to the declining trend in rest of South Asia. Spatiotemporal analysis and disease risk factors are useful for understanding transmission mechanisms and predicting future disease distribution to facilitate control. In this study we analyzed data on cutaneous leishmaniasis cases from Sri Lanka from 2001 to 2019. We asked three important questions regarding the driving forces behind the intensified leishmaniasis transmission: 1) Are the transmission dynamics in different areas synchronized? 2) What is the role of neighboring-area dispersal in shaping transmission dynamics? 3) How important is climatic variability in transmission dynamics? We used a multi-step approach to answer these questions. In addition to cross-correlation analysis, we built a mixed spatiotemporal regression-autoregression model to analyze risk factors, which is unique in leishmaniasis research because the simplified model was also useful for predicting future disease distribution. We found that the incidence dynamics in different districts could be divided into three synchronized groups based on similarity. Risk factor analysis indicated that precipitation, neighboring-district dispersal, and local infection carryover played important roles in shaping transmission dynamics. The spatiotemporal model predicted intensifying transmission with increasing case numbers, and expansion of high-transmission areas. Targeted interventions are urgently needed to stem the outbreak.

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Authors: D. P. W. Jayatunga,I. N. Harischandra,N. V. Chandrasekhara and B. G. D. N. K. de Silva

Journal: Life

The mosquito Anopheles (Cellia) subpictus sensu lato (s.l.) is a major secondary vector of malaria in Sri Lanka. The sibling species composition in this species complex in Sri Lanka remains debatable. Compensatory base changes (CBCs) in the secondary structures of internal transcribed spacer 2 (ITS2) are reliable sources to predict sexual incompatibility among closely related species. The objective of the present study was to investigate the An. subpictus s.l. populations in Sri Lanka using the CBC analysis. Mosquito DNA was amplified and sequenced for the ITS2 region. The sequences were annotated using ITS2 Database. ITS2 secondary structures were constructed and analyzed for CBCs using various bioinformatics tools. The ITS2 regions consisted of two different lengths, 575 bp and 480 bp. The two CBCs and three hemi CBCs identified in the present study suggest that there may be at least two sexually incompatible sibling species. In conclusion, it is likely that there may be only two reproductively isolated sibling species in the An. subpictus species complex in Sri Lanka. However, due to high divergence of ITS2 in these species, it is reasonable to assume that they may be undergoing a speciation event to separate as a distinct species.