Tharmasegaram Tharmatha
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Research Subjects
Tharmasegaram Tharmatha has a total of 9 co-authors. Here are the top co-authors by number of shared publications:
- Pavillupillai J Jude
Department of Zoology, Faculty of Science, University of Jaffna, Jaffna, 40000, Sri Lanka
2 shared publications - Ranjan Ramasamy
ID-FISH Technology, 556 Gibraltar Drive, Milpitas, CA 95035, USA
2 shared publications - Sinnathamby Noble Surendran
Department of Zoology, University of Jaffna, Jaffna, Sri Lanka
2 shared publications - Gobika Sivasubramaniyam
Department of Chemistry, Faculty of Science, University of Jaffna, Jaffna, Sri Lanka
1 shared publication - Kanapathy Gajapathy
Department of Zoology, Faculty of Science, University of Jaffna, Jaffna 40000, Sri Lanka.
1 shared publication - Meena Senthilnanthanan
Department of Chemistry, Faculty of Science, University of Jaffna, Jaffna, Sri Lanka
1 shared publication
Latest Publications
- Open Access
- 22 November 2012
- Published by Springer Nature in Parasites & Vectors
- Vol. 5 (1) , 269
Salinity-tolerant larvae of mosquito vectors in the tropical coast of Jaffna, Sri Lanka and the effect of salinity on the toxicity of Bacillus thuringiensis to Aedes aegypti larvae
Background: Dengue, chikungunya, malaria, filariasis and Japanese encephalitis are common mosquito-borne diseases endemic to Sri Lanka. Aedes aegypti and Aedes albopictus, the major vectors of dengue, were recently shown to undergo pre-imaginal development in brackish water bodies in the island. A limited survey of selected coastal localities of the Jaffna district in northern Sri Lanka was carried out to identify mosquito species undergoing pre-imaginal development in brackish and saline waters. The effect of salinity on the toxicity of Bacillus thuringiensis israelensis larvicide to Ae. aegypti larvae at salinity levels naturally tolerated by Ae. aegypti was examined. Methods: Larvae collected at the selected sites along the Jaffna coast were identified and salinity of habitat water determined in the laboratory. The LC50 and LC90 of B. thuringiensis toxin, the active ingredient of a commercial formulation of the larvicide BACTIVEC®, were determined with Ae. aegypti larvae. Bioassays were also carried out at salinities varying from 0 to18 ppt to determine the toxicity of Bacillus thuringiensis to fresh and brackish water-derived larvae of Ae. aegypti. Results: Larvae of four Anopheles, two Aedes, one Culex and one Lutzia species were collected from brackish and saline sites with salinity in the range 2 to 68 ppt. The LC50 and LC90 of B. thuringiensis toxin for the second instar larvae of Ae. aegypti in fresh water were 0.006 ppm and 0.013 ppm respectively, with corresponding values for brackish water populations of 0.008 and 0.012 ppm respectively. One hundred percent survival of second instar fresh water and brackish water-derived Ae. aegypti larvae was recorded at salinity up to 10 and 12 ppt and 100% mortality at 16 and 18 ppt, yielding an LC 50 for salinity of 13.9 ppt and 15.4 ppt at 24 h post-treatment respectively for the two populations. Statistical analysis showed significantly reduced toxicity of B. thuringiensis to fresh and brackish water-derived Ae. aegypti larvae at high salinities. Conclusion: A variety of mosquito vectors of human diseases undergo pre-imaginal development in brackish or saline waters in coastal areas of the Jaffna district in northern Sri Lanka. Salinity has a small but significant negative impact on the toxicity of B. thuringiensis toxin to Ae. aegypti larvae at salinity levels where Ae. aegypti larvae are found in the environment. This has implications for the use of B. thuringiensis toxin as a larvicide in brackish waters.
- 22 November 2012
- Published by Springer Nature in Parasites & Vectors
- Vol. 5 (1) , 269
Open AccessSalinity-tolerant larvae of mosquito vectors in the tropical coast of Jaffna, Sri Lanka and the effect of salinity on the toxicity of Bacillus thuringiensis to Aedes aegypti larvae
Background: Dengue, chikungunya, malaria, filariasis and Japanese encephalitis are common mosquito-borne diseases endemic to Sri Lanka. Aedes aegypti and Aedes albopictus, the major vectors of dengue, were recently shown to undergo pre-imaginal development in brackish water bodies in the island. A limited survey of selected coastal localities of the Jaffna district in northern Sri Lanka was carried out to identify mosquito species undergoing pre-imaginal development in brackish and saline waters. The effect of salinity on the toxicity of Bacillus thuringiensis israelensis larvicide to Ae. aegypti larvae at salinity levels naturally tolerated by Ae. aegypti was examined. Methods: Larvae collected at the selected sites along the Jaffna coast were identified and salinity of habitat water determined in the laboratory. The LC50 and LC90 of B. thuringiensis toxin, the active ingredient of a commercial formulation of the larvicide BACTIVEC®, were determined with Ae. aegypti larvae. Bioassays were also carried out at salinities varying from 0 to18 ppt to determine the toxicity of Bacillus thuringiensis to fresh and brackish water-derived larvae of Ae. aegypti. Results: Larvae of four Anopheles, two Aedes, one Culex and one Lutzia species were collected from brackish and saline sites with salinity in the range 2 to 68 ppt. The LC50 and LC90 of B. thuringiensis toxin for the second instar larvae of Ae. aegypti in fresh water were 0.006 ppm and 0.013 ppm respectively, with corresponding values for brackish water populations of 0.008 and 0.012 ppm respectively. One hundred percent survival of second instar fresh water and brackish water-derived Ae. aegypti larvae was recorded at salinity up to 10 and 12 ppt and 100% mortality at 16 and 18 ppt, yielding an LC 50 for salinity of 13.9 ppt and 15.4 ppt at 24 h post-treatment respectively for the two populations. Statistical analysis showed significantly reduced toxicity of B. thuringiensis to fresh and brackish water-derived Ae. aegypti larvae at high salinities. Conclusion: A variety of mosquito vectors of human diseases undergo pre-imaginal development in brackish or saline waters in coastal areas of the Jaffna district in northern Sri Lanka. Salinity has a small but significant negative impact on the toxicity of B. thuringiensis toxin to Ae. aegypti larvae at salinity levels where Ae. aegypti larvae are found in the environment. This has implications for the use of B. thuringiensis toxin as a larvicide in brackish waters.
- Open Access
- 22 December 2011
- Published by Springer Nature in Parasites & Vectors
- Vol. 4 (1) , 239
Molecular evidence for the presence of malaria vector species a of the Anopheles annularis complex in Sri Lanka
Anopheles annularis s.l. is a wide spread malaria vector in South and Southeast Asia, including Sri Lanka. The taxon An. annularis is a complex of two sibling species viz. A and B, that are differentiated by chromosome banding patterns and ribosomal gene sequences in India. Only species A is reported to be a malaria vector in India while the occurrence of sibling species in Sri Lanka has not been documented previously.
- 22 December 2011
- Published by Springer Nature in Parasites & Vectors
- Vol. 4 (1) , 239
Open AccessMolecular evidence for the presence of malaria vector species a of the Anopheles annularis complex in Sri Lanka
Anopheles annularis s.l. is a wide spread malaria vector in South and Southeast Asia, including Sri Lanka. The taxon An. annularis is a complex of two sibling species viz. A and B, that are differentiated by chromosome banding patterns and ribosomal gene sequences in India. Only species A is reported to be a malaria vector in India while the occurrence of sibling species in Sri Lanka has not been documented previously.