But now, the frogs were a literal source of uncleaness as well as typifying it as in Revelation 16:13.
"Ironically, the frogs infested the bedrooms and beds of the Egyptians; the very places where the blessings of Heqet were sought. It is somewhat amusing to picture the people of Egypt attempting to gingerly step over these millions of frogs as they walked about, afraid to crush any of these sacred animals beneath their feet. [Answers From the Book]"