A pig farm has several sick and dying adult pigs. Affected animals are febrile and depressed.
Some seem constipated and others have diarrhea. A few are ataxic.

A necropsy on one of the dead pigs shows widespread petechial and ecchymotic hemorrhages in the kidneys ("turkey egg kidneys"), bladder, spleen, and larynx.

Which one of the following choices is the most likely diagnosis?