"There is an horrible stench coming from this house that is so bad the neighbors a half block in any direction can no longer open their windows. And there's a rat problem now, too. What is the smell? Who knows? Cats/dogs/death?"
11 months, two acknowledgments, and dozens of comments later, we finally have our answer: chihuahuas.

According to an article about the incident on philly.com, the PSPCA had sent an investigator to the home earlier this year, but the owner barred the investigator from entering the home. The stench emanating from the home - horrible though it was - was not enough by itself to obtain a search warrant.
Despite reports that neighbors were reluctant to contact the authorities out of fear of reprisals from the dog-hoarder's family, commenters on the SeeClickFix thread note that there were "There have been at least 50 calls to ACT, the ASCPA, PETA, and the Humane Society about this home." Ultimately, a courageous SeeClickFixer named Leila was the one who gave Philadelphia Police the eyewitness account they needed in order to obtain a warrant - as she publicly acknowledges on the SeeClickFix issue's page.
The day after she called in, the police came. This is how one fixer described what they found: "You should have seen some of these animals that were pulled out; hairless, overgrown nails, @#$% encrusted in their paws, and it looked like a couple were blind. They had been living in 2.5 feet of their own feces."