How nosy mice sniff out sickness

The mystery of how some animals can sniff out sickness may have been solved. Ivan Rodriguez at the University of Geneva, Switzerland, and his colleagues have identified a type of smell receptor in mice that seems to respond to disease-related molecules produced by bacteria, viruses, or as the result of inflammation.

Several species of mammal, including mice, rats and dogs, are able to sniff out disease in humans and other animals. Researchers had previously identified four classes of receptor that mice and other mammals use to smell, but none of these provided an explanation for this phenomenon.

To see if any other receptors existed, Rodriguez's team took tissue from the vomeronasal organ – a pheromone-detecting sense organ found in the nasal cavity of mice, and some other mammals – and searched for genes expressing other possible smell receptors.

They identified five receptors closely related to a class of receptor already known to help immune cells hone in on pathogens and inflammation.

Further experiments showed that these vomeronasal receptors could be activated by molecules related to disease, which are excreted in urine when animals are sick.

Nose for illness

The next step is to destroy these receptors and see if the mice can still sniff out disease.

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