The sick ants stay away from their colleagues to prevent the spread of the disease

Wendy Kreeftenberg, Buiten-beeld / FLPA

By Sam Wong

Would you like your colleagues who cough and sneeze to stay away from the office? Unlike some humans, ants seem to understand the importance of avoiding others when they are infected. When forage ants are exposed to a fungal pathogen, they reduce their contact with workers inside the nest.

Nathalie Stroeymeyt at the University of Lausanne, Switzerland, and her colleagues studied the colonies of Lasius Niger ants using an automated ant tracking system.

The workers of these colonies are divided into nurses, who work inside the nest taking care of the brood, and in fodder, which collect food outside the nest. Foragers are more likely to get infections, but they interact less with other ants and rarely come into contact with those inside the nest.

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Killer mushroom

The researchers exposed some of the foragers to spores of Metarhizium brunneum fungus Spores attach to the ant cuticle and after a day or two, the fungus enters the ant and kills it.

In the day after exposure to the pathogen – before the ants get sick – the separation between the working groups was strengthened. Exposed forage changed their behavior, spending more time outside the nest and reducing contact with other workers. Farmers who were not exposed to the pathogen also took steps to isolate and the nurses moved the clutch deeper into the nest.

It's unclear how ants recognize infection, but they may be able to detect spores on other ants as well as on their own bodies.

The simulations show that these behavioral changes reduce the spread of infections and protect healthy workers and the queen from disease.

Such reactions are to be expected in social insects, since only the queen breeds. Evolution therefore favors individual behavior that benefits the entire colony.

"I think social insects could teach us ways to reduce disease transmission at the population level," says Stroeymeyt. Although she concedes that ants are good models only up to a certain point. "We can not really ask sick people to sacrifice themselves by dying in isolation as ants do."

Journal reference: Science , DOI: 10.1126 / science.aat4793

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