I truly understand your frustration as I have been hit by bed bug problem in the past as well. Frankly speaking I would trust the guest that he/she found bed bugs in the room, however the bed bugs MUST BE BROUGHT IN BY A GUEST. The problem is that the bugs might not be brought in by the same guest who discovered them, might be one who stayed before him/her. The guest who brought it in might not be aware of that at all.
I've heard some really nasty guests who purposedly bring bed bugs to airbnb properties to cause damage to hosts, but most guests who got bite are actually the victims of the bugs. I have done some research but found no way to 100% prevent such thing to happen from the host side, but there are some precautions we can do to minimize the possibility.
1. Put bug proof mattress encasement on the mattress and inspect it frequently, say every time doing cleaning and getting bed linens changed. As long as the encasement is intact the bugs cannot find too many places to hatch. There are some bug proof water proof encasement sold on Amazon for about $10-20 each they are pretty good.
2. Do some general pest control treatment periodically. You can hire a local pest control company and pay them a few hundred dollars a year for that, or you can do it yourself and save some cost. Visit this website and learn how to do it. **
3. Bed bug treatment is very problematic and you need to do it a few times, leaving 7-9 days in between so Airbnb set up the 21 days block for you to finish the treatment and ensure clear of bugs. That's going to hit you on the income, but it's better than getting every guest bite during this time.
As for the inspection, how did the exterminator conduct the inspection? I have asked some local pest control companies and they told me that the only way to ENSURE there's no bed bug is to conduct an inspection with a K-9 dog. Visual inspection can only find major infestation while it's almost impossible to find small amount of eggs hatched around the bed by human eyes.
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