HYGENE PROCEDURES. “A cast of small Atta workers is dedicated largely to the tending and cleaning of garden…Sequestration into discrete garden units also permits the ants to respond locally to disease, for example by sealing off an infected garden and thus prevent a pandemic spread of a disease throughout a nest.”
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0012668