Kathleen Corradi has several million furry problems on her hands and a bureaucracy to navigate. : One sunny afternoon in March, the city’s rat czar, Kathleen Corradi, came to Seward Park to survey her domain. It was treatment time for some rat burrows off Essex Street. Rats in this corner of the city have been known to cross the avenue in groups and bang up against the door of a taco shop. Exterminators for the Parks Department wheeled a BurrowRx machine to an area of low-lying greenery. “Perfect rat habitat,” Corradi said. “When something’s above them, they are happy.