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Exposure to artificial light at night has been shown to affect the immune responses of some birds, and now a study has found that light pollution can extend the infectious period of West Nile virus in house sparrows.
“These birds are a main reservoir of West Nile virus in nature. Mosquitoes will preferentially feed on some of these birds, and they live in urban, light-polluted habitats,” says Meredith Kernbach at the University of South Florida. “They’re likely one of the species that plays a key role in West Nile Virus transmission in light-polluted areas.”
She and her colleagues captured 45 wild house sparrows at two sites near Tampa Bay, Florida. They housed 22 of them in natural light conditions and 23 of them in artificial light conditions, using warm light similar to that used in homes and street lamps. They exposed all the birds to West Nile virus and then, over the next 10 days, measured their blood samples for infection and their body mass. The sparrows housed with artificial light at night remained infectious longer than the birds housed under natural lighting conditions. According to the researchers’ calculations, this makes an outbreak of disease among sparrows 41 per cent more likely if the birds are exposed to artificial light. This, in turn, might make it more likely that the virus could jump to humans via mosquitoes that bite both sparrows and humans.
It’s important to understand the relationship between artificial light and infectious diseases like West Nile virus, because we can make changes to disrupt these affects, she says. “We know there’s a West Nile virus seasons, so we could work with public works departments to turn off lights during the highest risk months,” she says.
Published 24 July 2019 in the Proceedings of the Royal Society:
