The effects of sleep deprivation on susceptibility to parasitic infection in Drosophila nigrospiracula

Sleep serves an essential function, and as such sleep deprivation has numerous negative effects on a wide range of organisms, including Drosophila. The link between sleep and cellular/humoral immunity is well studied, but behavioural immunity has been neglected for the most part. Here, we investigate the role of sleep deprivation on Drosophila nigrospiracula susceptibility to parasitism by the ectoparasitic mite, Macrocheles subbadius. We tested the hypothesis that sleep deprivation reduces behavioural resistance against mites, resulting in higher rates of infection among sleep-deprived (SD) flies compared to non-sleep-deprived flies, and that this is mediated by lower endurance (in negative geotaxis assays) among SD flies. We tested the impact of sleep deprivation on two age groups, flies 14 and 21 days post-eclosion. The prevalence of infection was 15% higher and mite abundance nearly 3x higher in older flies compared to younger flies. Moreover, older sleep-deprived flies experienced increased susceptibility to infection and lower climbing endurance compared to control flies. 21-day-old SD flies were 11% more likely to be infected and accumulated nearly double the number of mites as control flies. As such, we performed endurance assays on 21-day-old flies; control flies were 1.7x more likely to initiate climbing and climbed 6x longer in duration than SD flies. Taken together, our results show that increased susceptibility to parasitism among sleep-deprived flies is mediated by a concomitant decline in endurance. These findings contribute to our understanding of the importance of sleep and consequently the adverse effects of sleep deprivation on animals, particularly with regard to behavioural immunity.