Tenants found a bed bug

[Elisha Cram]

My tenant just informed me he found a bed bug and asked permission to use a fogger. It is the only apartment in an owner-occupied building. Any advice for dealing with bed bugs? I am getting exasperated with these tenants. They are genuinely nice guys, but they are slobs. They had a rat about 6 months ago, which we got rid of, and I counseled them at that time about not leaving food out and about keeping their apartment tidier. I have lived in this house since 2002 and had multiple tenants, and no issues with vermin of any kind prior to these tenants. I try not to be too uptight, as I am by no means a perfect housekeeper myself, but I am considering cleanliness inspections for these two. A quick Google search about bed bugs has me terrified. I am concerned they will continue to keep a cluttered and nasty apartment and then I will soon have bed bugs also. I admit to being ignorant on the topic. I simply have no experience here. Has anyone had a similar experience who can advise on how you handled it? Can anyone talk me down from the ledge, or should I be more terrified than I already am...?