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Insecticide susceptibility and dengue vector status of wild Stegomyia albopicta in a strategically important area of Assam, India

BACKGROUND: Dengue vector control programmes are facing operational challenges due to resistance against commonly used insecticides throughout the endemic countries. Recently, there has been appreciable increase in the dengue cases in India, however, no recent data are available on susceptible statu...

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Bibliographic Details
Published in:Parasites & vectors 2014-07, Vol.7 (1), p.295-295
Main Authors: Dhiman, Sunil, Rabha, Bipul, Yadav, Kavita, Baruah, Indra, veer, Vijay
Format: Article
Language:English
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Summary:BACKGROUND: Dengue vector control programmes are facing operational challenges due to resistance against commonly used insecticides throughout the endemic countries. Recently, there has been appreciable increase in the dengue cases in India, however, no recent data are available on susceptible status of dengue vectors. We have studied the susceptibility level of St. albopicta to commonly used insecticides in India. Adult mosquitoes were tested for the presence of dengue virus. METHODS: St. albopicta larval bioassays were carried out to determine the lethal concentrations (LC₁₀, LC₅₀and LC₉₉) and the resistance ratios (RR₁₀, RR₅₀and RR₉₉) for temephos. Susceptibility to 4% DDT, 0.05% deltamethrin and 5% malathion was assessed following standard procedure. Knock-down times (KDT₁₀, KDT₅₀and KDT₉₉) were estimated and knock-down resistance ratios (KRR₁₀, KRR₅₀and KRR₉₉) were calculated. VectorTest™ dengue antigen assay was used to detect the dengue virus in the field collected mosquitoes. RESULTS: In larval bioassays, the RR ranged from 1.4 (for RR₉₉) to 1.7 (for RR₅₀), which suggested that the tested St. albopicta were susceptible to temephos. There was no deviation among the lethal concentration data from linearity (r² = 0.61). Adult St. albopicta mosquitoes were resistant to DDT, while fully susceptible to deltamethrin and malathion. The knock-down values (KDT₁₀, KDT₅₀and KDT₉₉) obtained for DDT displayed straight line in log-dose-probit analysis and follow linear regression model. The KRR₉₉for DDT was 4.9, which indicated a 4.9 folds increase in knock-down resistance to DDT. However, for malathion and deltamethrin, the KRR₉₉values were 1.6 and 1.5 respectively suggesting that mosquitoes were knock-down sensitive. None of the mosquito pool was dengue virus positive. CONCLUSION: St. albopicta showed resistance to DDT and reduced sensitivity to deltamethrin and malathion. This data on insecticide resistance could help public health authorities in India to design more effective vector control measures. More dengue vector specimens need to be scanned to identify the potential dengue vector.
ISSN:1756-3305
1756-3305
DOI:10.1186/1756-3305-7-295