Luminous mice help track disease path

It may seem like a case of scientists with too much time on their hands – but researchers have dusted mice with fluorescent talcum powders to show which mice are likely to spread a disease which is potentially fatal to humans.

A little flourescent powder and patience can go a long way in epidemiology

Researchers based at the University of Utah looked at the spread of Hantavirus amongst wild deer mice and proved that bigger, older mice are responsible for most of the disease cases. In order to study the spread of the disease, the scientists covered groups of wild deer mice with a harmless fluorescent talcum powder in an array of colours. It was then possible to record their interactions with other mice and see when they had fought or mated: because they left telltale marks.

“If mice were in contact with a powdered mouse, you'd see the coloured bite mark on their ear or tail, or colour on their genitals.” Said Denise Dearing, a University of Utah professor of biology and senior author of the study published in Proceedings of the Royal Society B.

The scientists looked at a strain of the virus called Sin Nombre, which can spread from mice to humans - causing an often fatal lung condition. The virus also spreads between deer mice when they fight or mate.
Radio transmitters were implanted in other mice to track their contacts during the study, which is the first to show that the so-called "20-80 rule" applies to a disease that is directly transmitted among members of a single species of wildlife. The rule - which Dearing calls "more a concept than a rule" - says that a small fraction of a population - roughly 20% - accounts for most - about 80% - of disease transmission.

The study found that the mice that most frequently had contact with other mice averaged 11% heavier than the rest of the population. "Because Sin Nombre virus is transmitted through direct contacts, the results suggest that larger-bodied individuals are responsible for maintaining hantavirus in deer mice populations," Dearing said.