Olfactory learning and memory in the disease vector mosquito, Aedes aegypti

Olfactory learning in blood-feeding insects, such as mosquitoes, could play an important role in host preference and disease transmission. However, standardized protocols allowing testing of their learning abilities are currently lacking, and how different olfactory stimuli are learned by these insects remains unknown. Using a Pavlovian conditioning paradigm, we trained individuals and groups of Aedes aegypti mosquitoes to associate an odorant conditioned stimulus (CS), with a blood reinforced thermal stimulus (unconditioned stimulus; US). Results showed that the success of olfactory conditioning was dependent upon the CS and that mosquitoes’ ability to learn could interfere with the action of the insect repellent DEET. Results demonstrated that pre-exposure and the presence of DEET in the CS reduced the aversive effects of DEET. In addition, using cold-shock treatments and a protein synthesis inhibitor the nature of the formed memories was explored. Together, these results show that learning is a critical component in odor responses in Ae. aegypti, and provide the first evidence for the functional role of different memory traces in these responses.