It is early autumn, and your department receives a call from a rural GP practice about a 28-year-old man presenting with severe sore throat, odynophagia, and low-grade fever for five days.

 He reports eating undercooked wild rabbit meat at a hunting event last weekend.

 He was started on oral penicillin three days ago with no improvement.

On examination, his temperature is 38.2 °C, pulse 98 bpm, and BP 122/70 mmHg.

 The tonsils and soft palate appear ulcerated with a thick exudate, and several tender cervical lymph nodes are palpable bilaterally.

 There is no vesicular eruption, and no grey pseudo membrane is seen.

 He is systemically well and swallowing liquids.

Which of the following is the most likely diagnosis?