http://www.cdc.gov/ncidod/dbmd/diseaseinfo/cholera_g.htm#How%20does%20a%20person%20get%20cholera http://www.who.int/inf-fs/en/fact107.html http://vm.cfsan.fda.gov/~MOW/chap7.html I could find no mention any where of rats or mice being the cause of cholera I did find lots of information where they are used to test medicine and treatments for cholera So, maybe they can transmit it through their droppings if those get into food or water sources but I don't know if that is really the way it works or not. I think the rats and mice spread other diseases but maybe not cholera during that time. They may be guilty by association because they live in drains and sewers and in wet marshy areas quite a bit and that is a source of bad water and cholera. Hope this helps. Laura