Rats!!

[Tartar Horde]

Block up any holes you see with broken glass, be careful!! Scythe is right traps are the way to go, they will work all day and night. Shooting them is not at all efficient, makes you feel a bit better, but it will not solve your problem, merely reduce it till they breed themselves back into dominance. There's no shortcut to controlling Rats, it's a War of attrition where you have to destroy their food and shelter with grim determination. You have to respect the Rat, as nasty as they are they possess amazing powers of survival.