Infection avoidance behaviour: female fruit flies adjust foraging effort in response to internal and external cues of viral infection

Infection avoidance behaviours are the first line of defence against pathogenic encounters. Behavioural plasticity in response to internal or external cues can therefore generate heterogeneity in infection. We tested whether Drosophila melanogaster exhibits infection avoidance behaviour during foraging, and whether this behaviour is modified by prior exposure to Drosophila C Virus (DCV) and by the risk of DCV encounter. We examined two measures of infection avoidance: (1) the motivation to feed in the presence of an infection risk and (2) the preference to feed on a clean food source over a potentially infectious source. We found no clear evidence for preference of clean food sources over potentially infectious ones. However, infection avoidance was present in female flies, which were less motivated to feed when presented with a risk of encountering DCV, but this was only the case if they had been previously exposed to this viral pathogen. We discuss the relevance of plasticity in avoidance behaviours during ecologically relevant scenarios such as foraging for host fitness and pathogen spread.