Night-time lights bring insects, disease
Use of artificial lighting at night can change human and insect behaviors, increasing the risk of insect-borne disease.
Consider that before gas street lamps and electric light bulbs were invented in the 1800s, the world settled into darkness after sunset, relying only on the moon and stars for light.
That is still the case in more remote regions of the world. But, as artificial lighting spreads through these mostly tropical areas, research is showing how night-time light can alter human and insect behavior and bring about some unexpected results — an increase in the transmission of insect-borne diseases.
Altering human and insect interactions is one example of how light pollution may be changing disease risk patterns. The evidence suggests researchers should consider this when conducting future studies of how diseases spread.
Many potentially fatal or disfiguring tropical diseases are caused by parasites that are transmitted to humans by the bite of a specific insect carrier. For example, kissing bugs carry Chagas' disease, mosquitoes bring malaria and sand flies transmit leishmaniasis. Biting often occurs at night.
Insects are generally attracted to artificial lights. The lights interrupt and confuse the insects' normal night-time navigational cues, such as moonlight. Insects may also have adapted their routine, using lights as signs that humans are near.
Researchers from Brazil combed the published scientific literature for studies that examined if artificial light is changing the way night-time biting insects convey disease to humans. Their efforts turned up three case studies with kissing bugs, mosquitoes and sand flies that support a link, although in some unexpected ways.
Better housing and insecticides have reduced the ability of kissing bugs to directly bite humans. Yet, Chagas' disease perpetuates. Kissing bugs — attracted to homes by artificial lights — pass the disease on to people by defecating on food grown close to houses and later eaten by people. Kissing bugs also bite animals such as opossums or pets, which maintain the parasite's life cycle in areas where people live.
Image from NASA shows just how pervasive night lighting is becoming, on a global scale.