Bt Research 2025, Vol.16, No.6, 251-258 http://microbescipublisher.com/index.php/bt 252 sustainably reduce the incidence of diseases. By addressing the limitations of current vector control, this study helps to develop innovative, effective and acceptable biological control strategies within the framework of integrated vector control. 2 Fundamental Characteristics and Insecticidal Mechanism of Bacillus thuringiensis (Bt) 2.1 Biological features and classification of Bt strains Bt is not a recent trend. As an insecticidal tool, it has been used in agriculture and public health for many years. This type of bacteria is Gram-positive and can form spores. The key lies in the fact that it incidentally "produces" insecticidal proteins during this process. Interestingly, there are significant differences among various Bt strains, mainly depending on which insecticidal genes they carry and what the crystal proteins they produce look like. Some strains only target a certain type of insect, while others have a broader range, such as showing decent activity against Lepidoptera, Coleoptera and diptera insects. For instance, the BtG strain has been found to possess a relatively unique combination of cry genes, which makes its insecticidal ability stronger. Overall, Bt is relatively environmentally friendly, so it is increasingly being used as a "green insecticide" (Arsov et al., 2023). 2.2 Types and functions of insecticidal crystal proteins (Cry, Cyt, Vip) produced by Bt The insecticidal function of Bt, in the final analysis, still depends on several types of toxic proteins it produces. These three main types are Cry, Cyt and Vip. Among them, the Cry protein is perhaps the most well-known - because it generates encapsulated crystals during spore formation and its insecticidal mechanism has been studied most thoroughly. The Cry protein binds to specific receptors in the insect's intestine, and the killing effect begins here. In contrast, although the Cyt protein does not have such a strong effect on its own, when combined with Cry, it can enhance the toxic effect. Vip protein is slightly special. It is not produced when spores are formed but begins to be generated during the nutritional period. It also has another feature, which is that it can be effective against pests that have already been "immune" to Cry. This is particularly important in resistance management. Especially Vip3, whose efficacy against lepidoptera pests has been verified many times, is often found in genetically modified crops along with Cry (Palma et al., 2014; Bravo et al., 2017; Gupta et al., 2021). 2.3 Mechanism of Bt toxins: from ingestion to death of target insects The process of pest control is not as simple as "swallowing it in one gulp and dying immediately". Bt toxin must first be ingested by the larvae of pests before it can be activated by proteases in the intestines. The activated toxins do not wander around randomly but will target specific receptors, such as cadherin, aminopeptidase, and ABC transporters, to bind at these "docking interfaces". Next, the toxin molecules polymerize into larger structures, insert into the cell membrane, make holes, disrupt the ionic balance, and eventually cause the cells to die, paralyze the intestines, and the insects naturally cannot hold on. As for Vip3, its process is slightly different. It needs to be cleaved by proteases and restructured to take on a needle-like shape before being inserted into intestinal cells. Interestingly, this process is more complex than Cry, but precisely because of the differences, Vip toxins have become an important supplement in resistance management. Understanding these mechanisms is not only for the fun of research, but can indeed provide practical ideas for improving the effect of Bt and delaying the emergence of drug resistance (Pardo-Lopez et al., 2013; Nunez-Ramirez et al., 2020). 3 Vectors of Vector-Borne Diseases and Target Insect Species 3.1 Mosquitoes (e.g., Aedes aegypti, Culex spp.) and virus transmission (e.g., Dengue, Malaria) When it comes to vector-borne diseases, the first thought that mostly comes to mind is "mosquitoes". Indeed, such insects can be seen almost everywhere in the chain of disease transmission. Mosquitoes like Aedes aegypti and Culex are not only carriers of dengue fever, but also the main drivers of a series of diseases such as Zika, chikungunya fever and even West Nile virus. Anopheles mosquitoes play another "role", mainly responsible for the transmission of malaria. The problem is not only that there are many types, but also that the types of pathogens they spread are very diverse, including viruses and parasites. With global warming and the expansion of human activities, the geographical distribution of these mosquitoes is also constantly expanding. Areas that were previously uncommon have now become high-risk zones. It is not to say that all mosquito species are equally
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