These Are the Most Vermin-Filled Cities in the U.S.

Tampa, Fla., is among the roachiest big cities in America. Seattle may be the rattiest. Philadelphia has more mouse sightings per housing unit than any other U.S. city. These are some of the filthy highlights from the U.S. Census Bureau's biennial accounting of rat, mouse, and cockroach sightings across the country. The most recent numbers, collected in 2013, were released last month.

The data comes from the American Housing Survey, which is conducted every two years. And it does have limitations. For one, the survey includes only households, so sightings in public areas like subways and sidewalks don't count. And in each installment, the Census breaks down detailed data for only 25 metropolitan areas. This year, the list included Chicago, Houston, and New York—but it didn't include Dallas, Los Angeles, or San Francisco.