Does Tap Water Quality Compromise the Production of Aedes Mosquitoes in Genetic Control Projects?

SIMPLE SUMMARY: Scientists all over the world are continually rearing and producing insects in laboratories for many purposes including pest control programmes. Aedes aegypti and Ae. albopictus are mosquitoes of public health importance due to their ability to vector human and animal pathogens and thus vector control represents an important component of many disease control programmes. Water is a factor of great importance in the larval environment of mosquito species. However, obtaining sufficient water of reliable quality for mosquito rearing is still challenging, especially in developing and least developed countries, where access even to clean drinking water is limited. In prospect of cost-effective methods for improved mass-rearing toward SIT application, we assessed the impact of using tap water on the development and quality of Aedes mosquitoes. Results showed that, tap water with hardness/electrical conductivity beyond certain levels (140 mg/l CaCO(3) or 368 µS/cm) was shown to have a negative impact on the production of Ae. albopictus and Ae. aegypti mosquitoes. These results suggest that the quality of water should be checked when using for rearing mosquitoes for release purposes in order to optimize the production performance of mass-rearing facilities. This may have important implications for the implementation of the sterile insect technique in areas where reverse osmosis water is a scarce or costly resource. ABSTRACT: A mosquito’s life cycle includes an aquatic phase. Water quality is therefore an important determinant of whether or not the female mosquitoes will lay their eggs and the resulting immature stages will survive and successfully complete their development to the adult stage. In response to variations in laboratory rearing outputs, there is a need to investigate the effect of tap water (TW) (in relation to water hardness and electrical conductivity) on mosquito development, productivity and resulting adult quality. In this study, we compared the respective responses of Aedes aegypti and Ae. albopictus to different water hardness/electrical conductivity. First-instar larvae were reared in either 100% water purified through reverse osmosis (ROW) (low water hardness/electrical conductivity), 100% TW (high water hardness/electrical conductivity) or a 80:20, 50:50, 20:80 mix of ROW and TW. The immature development time, pupation rate, adult emergence, body size, and longevity were determined. Overall, TW (with higher hardness and electrical conductivity) was associated with increased time to pupation, decreased pupal production, female body size in both species and longevity in Ae. albopictus only. However, Ae. albopictus was more sensitive to high water hardness/EC than Ae. aegypti. Moreover, in all water hardness/electrical conductivity levels tested, Ae. aegypti developed faster than Ae. albopictus. Conversely, Ae. albopictus adults survived longer than Ae. aegypti. These results imply that water with hardness of more than 140 mg/l CaCO(3) or electrical conductivity more than 368 µS/cm cannot be recommended for the optimal rearing of Aedes mosquitoes and highlight the need to consider the level of water hardness/electrical conductivity when rearing Aedes mosquitoes for release purposes.