Abstract
BackgroundManagement of large quantities of eggs will be a crucial aspect of the efficient and sustainable mass production of mosquitoes for programmes with a Sterile Insect Technique component. The efficiency of different hatching media and effectiveness of long term storage methods are presented here.MethodsThe effect on hatch rate of storage duration and three hatching media was analysed: deionized water, boiled deionized water and a bacterial broth, using Two-way ANOVA and Post hoc Tukey tests, and the Pearson correlation coefficient was used to find the effect on the proportion of collapsed eggs. Two long term storage methods were also tested: conventional storage (egg paper strips stored in zip lock bags within a sealed plastic box), and water storage (egg papers in a covered plastic cup with deionized water). Regression analyses were used to find the effect of water storage and storage duration on hatch rate.ResultsBoth species hatched most efficiently in bacterial broth. Few eggs hatched in deionized water, and pre-boiling the water increased the hatch rate of Ae. aegypti, but not Ae. albopictus. A hatch rate greater than 80 % was obtained after 10 weeks of conventional storage in Ae. aegypti and 11 weeks in Ae. albopictus. After this period, hatching decreased dramatically; no eggs hatched after 24 weeks. Storing eggs in water produced an 85 % hatch rate after 5 months in both species. A small but significant proportion of eggs hatched in the water, probably due to combined effects of natural deoxygenation of the water over time and the natural instalment hatching typical of the species.ConclusionsThe demonstrated efficiency of the bacterial broth hatching medium for both Ae. albopictus and Ae. aegypti facilitates mass production of these two important vector species in the same facility, with use of a common hatching medium reducing cost and operational complexity. Similarly the increased hatch rate of eggs stored in water would allow greater flexibility of egg management in a large programme over the medium term, particularly if oxygenation of the water by bubbling oxygen through the storage tray could be applied to prevent hatching during storage.
Highlights
Management of large quantities of eggs will be a crucial aspect of the efficient and sustainable mass production of mosquitoes for programmes with a Sterile Insect Technique component
Methods such as the Sterile Insect Technique (SIT) using irradiated males [3,4,5], the Incompatible Insect Technique (IIT) using Wolbachia-infected males [6,7,8] or use of genetically modified mosquito strains such as those carrying RIDL constructs [9,10,11] are potential tools for inclusion in area-wide integrated pest management (AW-IPM) programmes aiming to suppress natural mosquito populations
Eggs from the DW and boiled deionized water (BDW) treatments were afterwards submerged in bacterial broth (BB) to determine whether the low hatch rate was really due to the hatching medium and not due to the quality of the egg batches
Summary
Management of large quantities of eggs will be a crucial aspect of the efficient and sustainable mass production of mosquitoes for programmes with a Sterile Insect Technique component. Researchers are seeking effective and environmentally friendly methods to control arthropod-borne diseases, as the effectiveness of traditional chemical insecticides is weakened by increasing insecticide resistance, and due to concerns about negative side effects on non-target species and environmental pollution [1, 2] Methods such as the Sterile Insect Technique (SIT) using irradiated males [3,4,5], the Incompatible Insect Technique (IIT) using Wolbachia-infected males [6,7,8] or use of genetically modified mosquito strains such as those carrying RIDL constructs [9,10,11] are potential tools for inclusion in area-wide integrated pest management (AW-IPM) programmes aiming to suppress natural mosquito populations. Key aspects of egg management will be the ability to store eggs whilst maintaining high viability over time, and to achieve a high rate of hatching when required
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