PLE-3569

A previously healthy 37-year-old man comes to the physician because of fever, generalized muscle aches, and an ulcer on his neck. The ulcer began 10 days ago as a painless, itchy papule that enlarged over a 2-day period. Small, fluid-filled blisters formed on top of the papule. The blisters broke down, forming a painless ulcer covered by a black scab. He is employed as a postal worker, and his hobby is gardening. He also takes care of several cats at home. What is the most likely diagnosis?