Mosquitoes Can Smell You Better at Night

Anyone who has had a nice evening outside ruined by an onslaught of bloodthirsty mosquitoes may now have a better explanation for why -- the pests can smell you better at night.

According to research published in the Nature journal Scientific Reports, a chain of proteins in the mosquitoes which enable the blood suckers to smell humans appears in higher concentrations at night.

"Just think, during the day the mosquito is sleeping and doesn't need to smell you. But when the sun goes down, the mosquito's olfactory system becomes extra-sensitive, and she is ready to smell and then bite you," said Samuel Rund, a doctoral candidate involved with the research.

To reach their conclusion the researchers, led by Giles Duffield and Zain Syed of the University of Notre Dame's Eck Institute for Global Health, examined the mosquitoes' ability to smell over a 24-hour day.

Their work focuses on odorant-binding proteins (OBPs), which are thought to help the insects concentrate on odor molecules and assist in carrying the molecules to the mosquito's olfactory receptors, which it uses to detect odors. The OBPs were showen to have higher concentrations in the mosquitoes' sensory organs at night than during the day.

The revelation that the OBPs are tied to a daily rhythmic cycle "could change the way we look at protecting ourselves from these disease-carrying pests," the researchers reported.

They contend their work is the first to show the role of daily rhythms in the sensory biology of mosquito species Anopheles gambiae, which is the primary type responsible for transmitting malaria in sub-Saharan Africa. Each year the region sees 300 million malaria infections and 1 million deaths from the disease.

"The fact that these studies were conducted in Anopheles gambiae mosquitoes has important implications for the development of novel insect control methods with the potential to reduce the transmission of malaria parasites and thus the morbidity and mortality associated with malaria disease," the researchers wrote. "This work provides the first comprehensive evidence of the important role of daily rhythms in the sensory biology of Anopheles gambiae and the implications for developing new control methods."