/Light pollutions effects on birds may help to spread West Nile virus

Light pollutions effects on birds may help to spread West Nile virus

sparrow

Light pollution leaves sparrows more vulnerable to West Nile virus

Claude Mondestin / 500px/Getty

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.

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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.

“There’s an avian hormone synonymous to cortisol in humans, which is responsible for mediating responses to stressors in birds. We thought that may be dysregulated, but we found that this hormone was not affected by light at night, so we’ve begun investigating melatonin as the possible hormone behind this,” says Kernbach.

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.

This effect could change under different lighting conditions as well, and Kernbach says research into the specific kinds of light that may not affect stress hormones is needed.

Journal reference: Proceedings of the Royal Society B, DOI: 10.1098/rspb.2019.1051

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