Evaluation of the effectiveness of Aquatain, Bacillus thuringiensis var. israelensis, and Temephos Anopheles arabiensis and Anopheles stephensi larvae in the laboratory and field settings.

Abstract

<title>Abstract</title> <bold>Background</bold>: The main tools for the control of malaria vectors in sub-Saharan Africa (SSA), including Ethiopia are long lasting insecticidal nets and indoor residual spraying. However, the sustainability of IRS and ITNs is threatened by the emergence of insecticide resistances, behavioral avoidance, as well as presence of outdoor biting mosquito populations. Thus, complementary interventions such as larval source management (LSM), which includes larviciding, are required to achieve better result in malaria vector control. This study aimed to evaluate the efficacy of three larvicides (Aquatain AMF®, temephos and <italic>Bacillus thuringiensis var. israelensis </italic>(<italic>Bti</italic>) against larvae of <italic>Anopheles arabiensisi</italic> and <italic>An. stephensi</italic>. <bold>Method</bold>: The tests were conducted in the laboratory and in semi-natural habitats on the 3^rd and 4^th larval instars of both insectary-reared and wild-collected immature <italic>Anopheles</italic> mosquitoes, respectively. For the field study, larvae were collected from three sites (Awash Sebat Kilo, Metahara and Adama towns). Three productive larval habitats in three villages were treated with Aquatain, temephos and <italic>Bti</italic>, and compared with untreated habitats (control). <bold>Results</bold>: In the laboratory, the percent mortality ranged 95% to 100% and 60% to 100% for <italic>An. arabiensis</italic> and <italic>An. stephensi</italic> colonies, respectively, while the percent larval mortality ranged 97% to 100% and 74% to 100% for field collected wild <italic>An. arabiensis</italic> and <italic>An. stephensi,</italic> respectively. In the natural field study, the percent immature stages reductions ranged 84% - 96%, 89% - 95% and 77% - 96% at Awash, Metahara and Adama respectively. The three larvicides (Aquatain, Temephos and <italic>Bti</italic>) clearly showed high larviciding efficacies both in the laboratory and field evaluations. Despite its efficacy, temephos changed the color of the water to whitish and has got strong smell. As a result, the community scared of the treated habitats. <bold>Conclusion</bold>: It is highly recommendable that Aquatain and/or <italic>Bti </italic>larvicides be used in malaria control program as complementary malaria vector control tools.