This rat still spawns and can be found in one of two different places: the area directly northwest of the windmills (650.00, -450.00, 55.00) and the area around the northwestern-most kobold camp (1500.00, 900.00, 30.00). She has the appearance of a normal rat.
She starts off dubious, but upon trading her the Vial of Infectious Disease you get as part of the Bertoxxulous Initiate quest she immediately de-spawns and a diseased female rat will spawn in her place and become aggro. If the diseased rat is a grey-con, it will not attack and simply de-spawn after a short period.
Edited, Sep 19th 2011 7:51pm by Rokon