Great Gerbils: A Plague on Their Houses

There is a recent study from Oslo University claiming that plague in Europe was largely introduced by Gerbil fleas rather than those of the maligned Black rat (http://www.theguardian.com/science/2015/feb/24/great-gerbils-chief-cause-of-the-great-plague-not-black-rats-study-says). The conclusion is based of the observation that fleas leave their rodents when host numbers decline and plague (which killed almost 30% of Europeans) showed fluctuations in incidence. The fluctuations were, however, not linked to populations of Black rats in Europe but to Great gerbils in Asia. The authors suggested that the fleas on the gerbils in times of host shortage leapt upon human traders using the Silk Route and consequently repeatedly carried plague into Europe. So the Black rat is innocent?