A 35-year-old woman came to a doctor with complaints of shortness of breath, deteriorated vision ("a haze before her eyes"), double vision, strabismus, nystagmus markedly dry mouth, nasal voice, difficulty swallowing, muscle weakness, and abdominal distension. According to her diet history, 20 hours ago she was eating canned meat and home-cooked fish. What is the most likely diagnosis in this case?