Autor(es): Jude Pavilupillai J, Tharmasegaram Tharmatha, Sivasubramaniyam Gobika, Senthilnanthanan Meena, Kannathasan Selvam, Raveendran Selvarajah, Ramasamy Ranjan, Surendran Sinnathamby N

Resumo: Dengue, chikungunya, malaria, filariasis - Japanese encephalitis are common mosquito-borne diseases endemic to Sri Lanka. Aedes aegypti - Aedes albopictus, the major vectors of dengue, were recently shown to undergo pre-imaginal development in brackish water bodies in the isl-. 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 - 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. Larvae collected at the selected sites along the Jaffna coast were identified - salinity of habitat water determined in the laboratory. The LC?? - LC?? 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 to 18 ppt to determine the toxicity of Bacillus thuringiensis to fresh - brackish water-derived larvae of Ae. aegypti. Larvae of four Anopheles, two Aedes, one Culex - one Lutzia species were collected from brackish - saline sites with salinity in the range 2 to 68 ppt. The LC?? - LC?? of B. thuringiensis toxin for the second instar larvae of Ae. aegypti in fresh water were 0.006 ppm - 0.013 ppm respectively, with corresponding values for brackish water populations of 0.008 - 0.012 ppm respectively. One hundred percent survival of second instar fresh water - brackish water-derived Ae. aegypti larvae was recorded at salinity up to 10 - 12 ppt - 100% mortality at 16 - 18 ppt, yielding an LC?? for salinity of 13.9 ppt - 15.4 ppt at 24 h post-treatment respectively for the two populations. Statistical analysis showed significantly reduced toxicity of B. thuringiensis to fresh - brackish water-derived Ae. aegypti larvae at high salinities. 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.

Palavras-Chave: Aedes aegypti; Bacillus thuringiensis; Dengue; Jaffna; Mosquito vectors; Salinity; Sri Lanka

Imprenta: Parasites & Vectors, v. 5, p. 269, 2012

Identificador do objeto digital: 10.1186/1756-3305-5-269

Descritores: Chikungunya virus - Pathogenesis ; Chikungunya virus - Viral infections ; Chikungunya Virus - Virus ; Chikungunya virus - Larvicide ; Chikungunya virus - Ovicida ; Chikungunya virus - Transmission ; Chikungunya virus - Dengue ; Chikungunya virus - Epidemiology ; Chikungunya virus - Public health

Data de publicação: 2012

INDICADORES

ACESSO