Malaria-causing mosquitoes are able be smell humans better at night, a new study has found.
The major malaria vector in Africa, the Anopheles gambiae mosquito, smells major human host odourants better at night, scientists said.
Anopheles gambiae is the primary species that is responsible for the transmission of malaria in sub-Saharan Africa, with approximately 300 million infections and 1 million deaths annually.
The study reported an integrative approach to examine the mosquito's ability to smell across the 24-hour day and involved proteomic, sensory physiological, and behavioural techniques.
Researchers from the University of Notre Dame's Eck Institute for Global Health and colleagues examined the role for a major chemosensory family of mosquito proteins, odourant-binding proteins (OBPs), in the daily regulation of olfactory sensitivities in the malarial mosquito.
It is thought that OBPs in the insect antennae and mouth parts function to concentrate odourant molecules and assist in their transport to the actual olfactory receptors, thereby allowing for odourant detection.
The team revealed daily rhythmic protein abundance of OBPs, having higher concentrations in the mosquito's sensory organs at night than during the day.
This discovery could change the way we look at protecting ourselves from these disease-carrying pests.
The study utilised mass spectrometry to quantify protein abundance in mosquito sensory organs, and electroantennograms to determine the response induced by host odourants at different times of the day.
The coincident times of peak protein abundance, olfactory sensitivity and biting behaviour reflect the extraordinarily fine-tuned control of mosquito physiology.
Olfactory protein abundance and olfactory sensitivity are high when needed (at night) and low when not required (daytime), researchers said.
The project was a follow-up to the team's earlier work that utilised genomic tools to reveal 24-hour rhythmic patterns of gene expression, including many genes involved in olfaction.
The study was published in the journal Nature: Scientific Reports.
