Background The larval bionomics of Aedes across the Jaffna peninsula in northern Sri Lanka was investigated to obtain information needed for developing more effective larval source reduction measures to control endemic arboviral diseases. Methods The habitats of preimaginal stages of Aedes mosquitoes were surveyed, and ovitrap collections were carried out in densely populated areas of the Jaffna peninsula. Aedes larval productivities were analysed against habitat characteristics, rainfall and dengue incidence. Adults emerging from collected larvae were tested for dengue virus (DENV). Results Only Aedes aegypti, Ae. albopictus and Ae. vittatus were identified in the field habitat collections and ovitraps. Aedes aegypti was the predominant species in both the field habitat and ovitrap collections, followed by Ae. albopictus and small numbers of Ae. vittatus. Tires and open drains were the preferred field habitats for Ae. aegypti, although larval productivity was higher in discarded plastic containers. The three Aedes species differed in field habitat preferences. Concomitant presence of the three Aedes species was observed in the field habitats and ovitraps. Larval productivities were inversely correlated with the salinity of the field habitat. Rainfall in the preceding month significantly correlated with larval productivity in the field habitats. DENV serotype 2 was detected in Ae. aegypti collected from ovitraps in the city of Jaffna. High Breteau, House and Container indices of 5.1, 5.1 and 7.9%, respectively, were observed in the field habitat surveys and ovitrap indices of up to 92% were found in Jaffna city. Conclusions Aedes larval indices in populated areas of the peninsula showed a high potential for dengue epidemics. Unacceptable littering practices, failure to implement existing dengue control guidelines, vertical transmission of DENV in vector mosquitoes and preimaginal development in brackish water and open surface drains, as well as in domestic wells that provide potable water, are serious constraints to the current Aedes larval source reduction methods used to control dengue in the Jaffna peninsula. Similar shortcomings in arboviral disease control are likely present in other resource-constrained tropical coastal zones worldwide.
Temporal and spatial information on land use/cover is a prerequisite for effective planning decisions in the context of social and economic development. Satellite remote sensing data have become increasingly important in the study of land use/cover changes. This paper uses multitemporal satellite data to measure and spatially characterize land use/cover changes in the Jaffna Peninsula, northern Sri Lanka over the two decades from 1984 to early 2004 in terms of potential drivers. Over this period, the Jaffna Peninsula has been impacted severely by armed conflict between the government of Sri Lanka and the Liberation Tigers of Tamil Eelam. A postclassification method is used to compare land use/cover classes from satellite images using Geographical Information Systems (GIS) to analyze the spatial pattern of land use/cover changes over the study period. Results indicate that the land use/cover pattern has been very dynamic since early the 1980s, showing a remarkable decrease in agricultural land use and concomitant increase in non-agricultural land uses. The ethnic conflict and its consequences, particularly large-scale population migrations, have been the main driving forces for such land use/cover changes in the Jaffna Peninsula. The results of this study are not only important in aiding efforts to reconstruct this area after decades of physical and socioeconomic devastation, but should also prompt similarly urgent studies in other inaccessible war-torn areas of the world.
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A random survey of aquatic Oligochaeta was conducted in Chennai, Villupuram, Dindugal, Thiruvallur, and Sivagangai districts of Tamil Nadu from November 2010 to March 2012. Thirteen taxa were identified from a total of 644 aquatic oligochaetes examined from various qualitative samples of aquatic vegetation and sediments. Chennai district had 3 families: Naididae, Pristinidae and Tubificidae along with a polychaete. The naidids were most diverse with 5 species: Branchiodrilus semperi, Aulophorus furcatus, Dero digitata, Dero indica and Dero zeylanica, the pristinids were represented by Pristina brevichaeta and Pristina jenkinae and the tubificids by 2 species, Branchiura sowerbyi and Limnodrilus hoffmeisteri. The nine aquatic oligochaetes collected from Chennai were already reported from this region. Two naidids, Branchiodrilus semperi and D. indica, along with the tubificid Branchiura sowerbyi, were collected from Villupuram district and they constitute the first reports for that district. Limnodrilus udekemianus from Kodaikanal, Dindugal district constitutes the first report for that region of Tamil Nadu. Megadriles belonging to the family Octochaetidae (Dichogaster bolaui?) and unidentified Megascolecidae collected from Thiruvallur and Sivaganga districts respectively were found to occur in aquatic habitats.
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