How to check for rats?

i live in apartments with a window air conditioner.I found what i think is rat droppings. i vacuumed under my bed & floor. i've looked under my furniture, and everything. Never saw or heard a rat. what i'm rlly worried about is under my bed, the felt the covers the box springs has 2 big rips in it. i've shoved a broomstick in them and saw nothing come out. my neighbor has field mice. i dont want to get a disease, like the plague or something. my room is clean enough not to carry vermon, it is a little cluttered. (piles of clothes) what do i do???