Rats is an neutral enemy in Strife. They have infinite hit points and scurry about sewers making cute noises and they can interact with water causing splashes etc. They are impossible to destroy and do not block movement/gun fire/line of sight. They have a simple search AI that causes them to seek out the player and follow him everywhere like a pied-piper. This could be a Original Strife: Veteran Edition bug and not a bug in the original edition.
It is possible that the developers intended the rats or at least one rat to be a usable item in some form. The source for this knowledge is the unused I_RATT Inventory icon for "Rat Buddy", which is not a collectible in any known version of the game. The image file can be seen here. The speculation is for what purpose. The term Buddy could have been intended as a companion / friend / tool that could have been used for various quest specific tasks. Like using one to crawl through the many hidden mouse hole like structures throughout many of the maps. These holes were considered audio paths for alerting guards. But could have doubled for the same purpose. One example is in the governor's office near the door. The term buddy could be based off the developers own internal humor only could have only been meant as a simple tool for various quests like distracting a guard to go crush them or by using them in key locations to spread the disease they mention often through out the story line. Or even for a sacrifice to prove something to the Order. The relative possibilities could have been endless. But one thing we do know is the development of the game was rushed halfway through and was one of the features cut.