Environmental persistence and transmission dynamics of Serratia AS1 in mosquito habitats: advancing paratransgenesis for malaria control.

UNLABELLED: Malaria remains a major global health challenge, particularly in developing countries, necessitating innovative control strategies. With rising resistance of Plasmodium to drugs and Anopheles mosquitoes to insecticides, paratransgenesis-using engineered symbiotic bacteria to deliver anti-pathogen molecules-offers a promising alternative. Translating this approach to field applications requires rigorous evaluation under semi-field conditions. We evaluated the environmental stability and transmission dynamics of Serratia AS1-mCherry, a paratransgenesis candidate, in Anopheles stephensi habitats under semi-field conditions in Bandar Abbas, Iran. Serratia AS1 successfully colonized mosquito midguts and ovaries, persisted in larval breeding water for 14 days, and remained stable on sugar-soaked cotton pads for 4-6 days. Transmission routes include transstadial, venereal, and vertical transmission, in addition to adult acquisition from larval habitats (sipping), demonstrating robust colonization and dissemination. Water-based delivery effectively disseminates Serratia AS1 among mosquito populations, highlighting its potential for paratransgenesis-based malaria control. This study establishes the feasibility of using Serratia AS1 with effector molecules in field settings, offering a sustainable strategy for managing vector-borne diseases.

IMPORTANCE: Malaria remains a major health challenge, especially in developing countries where traditional control methods like insecticides and drugs are becoming less effective due to resistance. This study explores a promising new approach called paratransgenesis, which uses genetically modified bacteria to fight malaria. We tested a bacterium called Serratia AS1, which can live inside mosquitoes and spread through their populations. Our experiments showed that Serratia AS1 can survive in mosquito breeding sites and spread effectively among mosquitoes through multiple routes, such as larval water, sugar sources, and even from parent mosquitoes to their offspring. These findings suggest that Serratia AS1 could be used to deliver anti-malaria molecules to mosquitoes in the wild, offering a sustainable and innovative way to control the disease. This work brings us one step closer to using paratransgenesis as a practical tool to reduce malaria transmission and save lives.