First field and laboratory trial of VectorBac® WG around the airport zone of the capital city of Libreville, Gabon

Context/Purpose: The urban ecosystem of Akanda behind the airport of the capital city of Libreville in Gabon, harbors diverse and dense mosquito larval habitats and hotspots for malaria and arboviruses transmission. To effectively conduct vector control, it is imperative to adopt an integrated approach by adding biolarvicides to the toolbox. The main objective of this study is to evaluate the efficacy of a biolarvicide under laboratory and field conditions. Methods: In Gabon, this current pilot and preliminary study sought to test the efficacy of the biolarvicide VectorBac® Water dispersable Granule (WG) (VBG) during the rainy season period (March to May 2024) under field and laboratory conditions following the 2005 World Health Organisation protocol. Results: For the bioassay of VBG, in the laboratory, the required dose to kill 88% and 100% of the larvae in rearing cups was 0.001 g/mL and 0.01 g/mL respectively. Under field conditions, the percentage larval density reduction irrespective of the microhabitat type ranged from 90 to 100% and the mosquito larval density reduction between test and control groups in the field differed statistically (X2=34; p = 0.026). Conclusion: The larvae from Akanda tested under field and laboratory conditions were very sensitive to the standard dose recommended by the manufacturer after 24 hrs post-treatment with VBG. This pilot study provides baseline information that is required to conduct a longitudinal study to evaluate the residual effect of VBG in different ecological settings in Gabon.