Avaliação da atividade larvicida de uma linhagem de Bacillus thuringiensis isolado de ambiente amazônico em condições de semicampo sobre populações de Aedes aegypti e em organismos não- alvo

Abstract

Aedes aegypti is the main vector of arboviruses that cause diseases such as dengue, zika, chikungunya, and urban yellow fever, representing a major concern for public health. Several measures are adopted to mitigate the impacts caused by this mosquito, including mechanical, chemical, and biological control. Bacillus thuringiensis (Bti) is an insect vector control agent for diseases and agricultural pests, widely used in biological control programs around the world. However, environmental factors such as ultraviolet radiation, pH, salinity, and temperature can affect its persistence, decreasing its biological plausibility in nature. In this context, finding new bacteria from the Amazon biome with bioinsecticidal potential is crucial for the implementation of new entomopathogenic agents in the region. The objective of this study was to evaluate the larvicidal potential of a Bacillus thuringiensis strain isolated from the Amazon environment under semi-field conditions and its toxicity in non-target organisms. This study was carried out at the Laboratory of Biological Control and Biotechnology of Malaria and Dengue (LCBBMD) of the Amazon Research Institute (INPA). The strains GD02.13-B. thuringiensis and AM65-52 (Bacillus thuringiensis var. israelensis) were used to evaluate their effects in the laboratory and semi-field. Mortality and chemical and physical factors, such as pH and temperature, were analyzed weekly for fifty days. Bacterial persistence was determined by counting viable colonies in comparison with the standard strain. The strains toxic to Aedes aegypti larvae were also tested on tadpoles of the genus Scinax, a non-target organism. The results showed that the cellular components of the GD02.13 strain were more efficient than those of the standard strain, both in laboratory and semi-field conditions. Exposure of tadpoles to the cellular components of the GD02.13 and AM65-52 strains did not result in mortality up to five days of evaluation. Therefore, the development of bacterial larvicides for biological control could be significant and cost-effective, with activity directed at target organisms, in addition to being promising as vector control measures for the mosquito A. aegypti.