Fruit flies learn to avoid odours associated with virulent infection

Area of Science:

• Animal behavior
• Pathogen-host interactions
• Neuroethology

Background:

• Learning to avoid toxic substances is common in many animals.
• However, the ability of animals to learn to avoid cues linked to infectious diseases is less understood.
• This study investigates pathogen-associated olfactory learning in insects.

Purpose of the Study:

• To determine if Drosophila melanogaster can learn to avoid olfactory cues associated with a virulent intestinal pathogen.
• To investigate if this learned avoidance is dependent on pathogen virulence.

Main Methods:

• Drosophila melanogaster were exposed to food containing a virulent pathogen (Pseudomonas entomophila) scented with a specific odorant.
• A control group was exposed to pathogen-laced food with a different odorant or an avirulent pathogen mutant.
• Subsequent olfactory preference tests were conducted to assess learned avoidance.

Main Results:

• Flies exposed to virulent P. entomophila associated the odorant with infection and subsequently avoided it.
• This learned avoidance was not observed when flies were exposed to an avirulent mutant of P. entomophila.
• The pathogen itself was not aversive to taste when directly added to food.

Conclusions:

• A virulent pathogen infection can serve as an aversive stimulus, enabling associative learning in flies.
• Drosophila can learn to associate food odors with pathogen contamination and reduce attraction to contaminated food.
• This demonstrates a novel mechanism for pathogen avoidance in insects mediated by learned olfactory cues.