https://youtu.be/xC3DJm9rFk4
The Vancouver Rat Project (VRP) was developed in 2011. The VRP’s goal has been to improve the understanding of populations and the harmful bacteria, viruses, and parasites circulating among the rats. Archeologically, city rats have been the source of a number of infectious diseases such as the plague. Very little is known about city rats or contemporary rat-related health risks. This is challenging because without an understanding of rats and the zoonotic microbes they carry, it is almost impossible to begin to measure the health threats posed to people, or develop a plan to eradicate the rodents. How rats move and interact with each other influences the spread of microbes. Some of their results suggest: 1) the risk of exposure to rats is site specific. 2) The amount of disease in the rat population may vary with season. 3) Bite wounds may result from aggression in mature rats. 4) Rats may carry microbes transmitted by ectoparasites: a parasite, such as a flea, that lives on the outside of its host. 5) Ear mites were likely introduced to Vancouver through international shipping.
http://www.delta-optimist.com/opinion/blogs/deltabc-1.983313/blog-vancouver-rat-project-1.2165770