Chironomid larvae, important hosts facilitating the persistence of Vibrio cholerae in water reservoirs of a cholera-endemic area of north Cameroon.

Introduction: chironomid larvae are present in aquatic systems, including freshwater, and often are important hosts for Vibrio cholerae. Chironomid larvae interact with V. cholera and may shield the bacterium from environmental stressors, resulting in its dissemination. This study aimed to determine the role of chironomid larvae in the persistence of V. cholera in the water reservoirs of a cholera-endemic area of Cameroon. Methods: chironomid larvae and water samples were collected from scoop holes of the Kaliao and Mizao temporary streams in Maroua during the cholera inter-epidemic (dry) season. V. cholera was isolated from chironomid larvae and water samples on thiosulfate citrate bile salt sucrose agar and biochemically identified. Water temperature, salinity, electrical conductivity, total dissolved solids, oxygen saturation, dissolved oxygen, and hardness (including calcium and magnesium) were analyzed for their influence on V. cholerae-larvae interactions. Results: Vibrio cholera was isolated in 45.45% of cases (95% CI: 32.5-58.9) from chironomid larvae. In contrast, 27.72% of water samples without larvae tested positive for V. cholera (95% CI: 18.4-38.6), only 4.54% of samples simultaneously harbored V. cholera in both larvae and water (95% CI: 1.2-11.3). The probability of detecting V. cholera was significantly higher in chironomid larvae than in water (p < 0.05), suggesting a strong ecological association. Furthermore, water samples with higher dissolved oxygen saturation (up to 91%) and elevated magnesium concentrations (up to 133.65 mg/L) were consistently V. cholerae-negative, suggesting a potential inverse relationship between these parameters and bacterial presence. Conclusion: the study highlights chironomid larvae as potential reservoirs for V. cholerae, emphasizing the need to monitor both larval habitats and water quality for better cholera surveillance and control in endemic regions.