Comparative Evaluation of Larvicides for Larval Source Management of Mosquitoes in Lagos, Nigeria.

Adetoro, Fouad A.; Anikwe, Joe C.; Makanjuola, Winifred A.; Omotayo, Ahmed I.; Awolola, Samson T.

doi:10.21608/eajbsa.2022.221971

Comparative Evaluation of Larvicides for Larval Source Management of Mosquitoes in Lagos, Nigeria.

Document Type : Original Article

Authors

¹ Department of Zoology, University of Lagos, Akoka, Yaba, Lagos, Nigeria.

² Department of Zoology, University of Lagos, Akoka, Yaba, Lagos, Nigeria

³ Department of Public Health and Epidemiology, Nigeria Institute of Medical Research, Yaba, Lagos, Nigeria. P.M.B 2013, Yaba, Lagos, Nigeria

10.21608/eajbsa.2022.221971

Abstract

The use of larval source management (LSM) in sub-Saharan Africa is limited, however, widespread report of insecticide resistance in adult mosquitoes has engendered renewed interest in LSM; especially larviciding. Hence, this study evaluated bioefficacy and residual efficacy of commercially available larvicides;Temephos, Spinosad, Bacillus thuringiensis var. isrealensis (Bti) and Bacillus thuringiensis var. israelensis/Bacillus sphaericus (Bti/Bs) on larvae of Anopheles gambiae s.l, Culex quinquefasciatus and Aedes aegypti in Lagos, Nigeria. Acute toxicity assay was used to determine LC₉₅ and the LC₉₅ was doubled to determine discriminating doses. Residual efficacy was assessed by exposing larvae to discriminating doses of larvicides in deionised water and in water collected from larval habitat for 28 days and 24 hr mortality post-introduction of larvae was checked for 2nd, 4th, 7th, 14th, 21st and 28th day. Probit analysis was used to estimate LC₉₅ and residual efficacy at mortality ≥95%. T-Test was used to determine the level of significance (P<0.05) of the residual effect. Temephos (0.007mg/l) was the most toxic considering 24h LC₉₅. The trend of LC₉₅ (Temephos < Spinosad < Bti/Bs < Bti) in Anopheles gambiae s.l was the same for Culex quinquefasciatus and Aedes aegypti. Residual effect of Bti/Bs > Bti > Temephos > Spinosad on mosquito larvae from Lagos, Nigeria. The trend of residual efficacy is the same in both bioassays albeit reduced when larvicides were dissolved in water collected from larval habitats. Strong bioefficacy and better residual capacity of Bti/Bs make it a better larviciding agent against Anopheles gambiae s.l, Culex quinquefasciatus and Aedes aegypti in Lagos, Nigeria.

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