Isn't that suppose to be one of the reasons the plague spread so far and fast? A major preditor of rats and mice wasn't around in sufficient numbers?
So essentially it goes..
Dark age Xtian fundyism -> Less cats -> Bubonic plauge -> labour shortage -> end of fuedalism -> renaissance...
Kind of satisfying in an ironic way that (at least in this case) there seemed to be a self righting mechanism.....