Figure 1.
West Nile virus infection viraemia, body mass and WNV-induced mortality results. Effects of experimental West Nile virus exposure on house sparrows (Passer domesticus) exposed to artificial light at night (ALAN; 8 lx during night hours for two to three weeks prior to WNV exposure) versus controls (animals kept on 12 L : 12 D for duration of experiment). Blue points and dashed lines signify ALAN-exposed individuals, and black points and solid lines signify controls. (a) Individuals exposed to ALAN had significantly higher viral titers on d6 post-exposure, indicated by the asterisk. The horizontal dashed light represents the conservative transmission threshold or the minimum amount of virus in circulation required to transmit WNV to a vector (i.e. 105 PFU). (b) Effects of WNV and ALAN on change in group mean body mass throughout the course of WNV infection. On d6, ALAN-exposed individuals lost appreciable mass whereas controls continued to gain body mass. (c) Relationship between WNV titre and body mass change on d6 post-WNV exposure. The vertical dashed line represents the WNV transmission threshold; individuals to the right of this dashed line are infectious to mosquitoes, and individuals to the left of this dashed line are not. Only ALAN-exposed individuals were infectious on d6. (d) No effect of ALAN on WNV-induced mortality. (Online version in colour.)