Biocontrol potential of Azolla pinnata for culex quinquefasciatus management in Uganda

Abstract

Background: Culex quinquefasciatus is a major vector for lymphatic filariasis (LF), a disease of great public health importance in Uganda. However, there is limited evidence on the biocontrol methods for Culex quinquefasciatus management in Uganda. This current study therefore, is aimed at assessing one of the potential biocontrol methods for Culex quinquefasciatus management in Uganda of which “the biocontrol potential of Azolla pinnata for Culex quinquefasciatus management in Uganda” is a prospective candidate Methods: The study was conducted from Makerere university lower invertebrate laboratory in February 2021. Four, one-litre plastic tanks were added with varying concentrations of Azolla pinnata in the following order, T1 (10 g in 500 ml), T2 (20 g in 500 ml), T3 (30 g in 500 ml), T4 (0 g in 500 ml), then 100 larvae at their second instar were introduced into each tank. The larvae were fed on fish feed and cat feed. Daily changes in pH, DOC, and number of larvae that emerge into adults in all water tanks were monitored. The concentration of Azolla pinnata was categorized as low (10 g), moderate (20 g,) high (30 g), and no Azolla (0 g). Percentage of larvae that emerged into adults were categorized as very low (<45%), moderate (≤55%), and very high (≥80%). Results: The results suggest that, number of larvae that emerged into adults greatly reduced with increasing concentration of Azolla pinnata (g/500 ml of water), that is to say, T1 (74 %), T2 (54 %) T3 (43 %). In addition, the effect of increasing Azolla pinnata infestation was: decreasing pH of infested water, (P< 0.05), (ii) increasing dissolved oxygen content (DOC) of water, (p˂ 0.05), and (iii) decreasing number of larvae that emerged into adults, (p˂ 0.05). Conclusion: These results suggest that high concentrations of fresh Azolla pinnata increases Culex quinquefasciatus larval mortality by reducing the pH of the infested water. Keywords: Culex quinquefasciatus, Azolla pinnata