79 Yr Old Father In Law, In Over All Good

79 yr old father in law, in over all good health, in late March had severe abdominal pains, chills,low grade fever. His family doctor diagnosed in clinic diverticulitis. He did a 3wk round of Cipro and another antibiotic I do not know the name of. His abdominal pains are gone but he continues with off and on low grade fever, chills just about every evening. He has lost 10lbs in the last 2 months. He has more and more fatigue daily. He has been borderline diabetic for yrs but controls it will diet and exercise and is well under control. He did have a triple bypass 6 yrs ago but has done great even with that. He just saw his cardiologist and was given a good report. He does stay active outside and is frequently in area woods as he is a retired timber supervisor and does consulting from time to time. He has had tick exposure through the yrs and recently had 3 he noticed on him. He is scheduled for an apt with his gastrointestinal doctor on Monday. Any suggestions on direction to go with for him. Thanks