Biological control of the mosquito Aedes aegypti

Methods

Summary

The project methods are simple and well established.  The entomopathogenic roundworm (ER) will be cultured to large numbers in insects (honeycomb moth and mealworm beetle). Insect larvae will be infected by the ER and killed within 1 or 2 days.  Upon death, the ER will multiply in the cadaver, from which hundreds of thousands of roundworms will emerge.  The roundworms will be collected and used in the assays against mosquito larvae.

Mosquito eggs will be kept in water at 26C to emerge. Hatched larvae will be let to molt until the stages L3 and L4. These are the larval stages susceptible to ERs.  Fifteen L3/L4 and 1,500 roundworms will be transferred to water-filled containers (floor drain, water reservoir, used tire, etc).  For each kind of container we´ll use 10 repeats, and each assay will be conducted twice.

The efficacy of the ER will be assessed 7 days later. The proportion of dead mosquito larvae will be assessed in the containers treated with ERs and in the blank controls.

Challenges

The major challenge will be to single out micro-environmental factors that may increase or decrease the efficacy of the ER.  The amount of water in the containers, its temperature and the direct sun incidence on outdoor settings (such as used tires and water reservoirs) may affect the efficacy of the ER, as it would happen to any biocontrol agent used against mosquito larvae.

Pre Analysis Plan

The data will be analysed through standard statistical tests to compare the proportion of dead mosquito larvae in the containers treated with ERs and in the blank controls.  If the roundworms get established in the containers overtime - through reproduction inside the dead mosquito larvae - regression analysis will be used to examine roundworm and insect larvae survival overtime.