All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
The most preponderant view of the scholars is that the urine and dung of animals whose meat is forbidden to eat, such as lions, cats and mice, are impure.
Therefore, the excrements of a mouse are impure; it is an obligation to wash the mat or clothes that are stained with it for whoever wants to pray. However, you do not have to wash the entire mat; it is sufficient for you to only purify the place that is stained with impurity.
If you are not sure about the exact spot where the mat has been stained with impurity, then you should wash the entire carpet unless the excrement and the place that is touched with the impurity are dry.
The excrements of cockroaches are pure because the dead cockroaches and other insects that do not have blood are pure. Ibn Qudaamah, said:
"Living beings that do not have blood ……do not become impure when they die, and the water in which they die does not become impure, according to the view of the majority of the jurists." [End of quote]
If a dead animal is pure, then its excrements are pure. Therefore, if any excrements (of such animals or insects) fall on the body or clothes of the praying person, or on his prayer mat, then this does not affect his prayer even if he does not remove it because they are pure. However, sewage cockroaches are an exception from this, because the scholars differed in opinion about it: some are of the view that they are pure and some are of the opinion that they are impure.
Allah Knows best.