The human-animal relationship was radically different in the Medieval period than now. The majority of Europeans now live in an urban or suburban setting and rarely interact with animals other than pets, pests or the meat on their plate. In Medieval Europe, even in the cities, people lived intimately with animals. Even in places such as London the streets were filled with rogue pigs, dogs, cats and draft animals and of course rats. They were far more commonplace and through the eyes of a medieval European did not warrant the same disgust as a modern person.

The category of 'vermin' is fluid, for instance, in this period otters were considered vermin and routinely killed as they were seem as poaching 'human food' i.e. fish but now they are generally considered cute and protected animals. Rats were pests primarily because they stole human food rather than any hygiene concerns during this period. They may seem obviously filthy and dangerous to us but in the context of Medieval Europe they were just another one of the many animals that humans shared their spaces with.

The animals that routinely had connotations of 'filth' attached to them were cats and dogs and around the times of plague, or the fear of an outbreak, they would be slaughtered en masse. Ironic since they were killing the most effective form of controlling the rat population and likely worsened the outbreak.

Medieval Europeans never figured out they were spreading the plague but they did associate them with it. Rats were seen as harbingers of the plague as many chroniclers commented that the dying rat was a sign that the plague was coming. Interestingly, many early epidemics have no mention of rats at all and in 2002 Samuel Cohn put forward evidence that the Medieval black death may not have been the bubonic plague at all and thus not spread by rats.

Some scholars now believe that the main culprit of the spread may have been gerbils rather than rats - so we are still to a certain extent debating and figuring out what spread the plague around Europe.

To summarise,

1. Rats were not as strongly associated with filth as they are now and the scapegoats were cats and dogs who were slaughtered in an attempt to prevent or curb the plague.

2. They did however see rats dying as a sign the plague was coming so had some understanding of their association.

Reading I'd recommend:

Emily Cockayne, Hubbub: Filth, Noise and Stench in England 1600-1770 (2007)

• Obviously it is a little later than the period you are asking about but still very useful.

Mary Fissell, 'Imagining Vermin in Early Modern England' , History Workshop Journal 47 (1999)

• Again a little later in the period but explains the fluidity of how animals were and are categorised.

Jonathan Burt, Rat (2006)

• A great and short read with a chapter dedicated to the rat and the plague.

Hannah Velten, Beastly London: A History of Animals in the City (2013)