The impact of environmental and host factors on wolbachia density and efficacy as a biological tool

Wolbachia, a bacterium found naturally in some species of Aedes and Culex mosquitoes, has gained significant attention for it's potential in controlling mosquito-borne diseases and suppressing mosquito populations. However, Wolbachia-mediated pathogen blockage, Wolbachia dynamics in field populations and vertical transmission have been reported to be density-dependent. Several factors, including host genetics, diet, temperature, and co-infections can influence Wolbachia titers within its host. The interplay between these factors can have significant influence on the effectiveness of Wolbachia-mediated pathogen blockage and cytoplasmic incompatibility. However, there is a knowledge gap regarding the regulation of Wolbachia density within its host, which could affect its effectiveness as a biocontrol tool. Therefore, this review aims to understand the complex tripartite association between the environment, host, and endosymbiont, and how these relationships are crucial in harnessing the full potential of Wolbachia as a biological tool. Further, we highlight how host, pathogen, and environmental factors influence Wolbachia density and how their interplay can impact CI and WMPB. We further review the strategies adopted to maintain/control Wolbachia densities in field populations.