As a person who travels and benefits from the charming and unique homes through AirBnB, I have mostly been good about picking hosts and stays that have been enjoyable. I want to share that I have experienced fleas at one of my stays. I grew up with pets, but hadn't experienced a flea infestation.
My stay was a second story apt, hardwood floors with area rugs, and on the surface, it appeared very clean, tidy and well appointed. Yes, the host allowed pets, but required proof of flea medication/treatment - this is now a red flag for me. Especially since I imagine fleas from a pet to a flea infestation likely takes time to develop.
Some keys points: I didn't initially notice it. I was there a couple days before I realized what was going on, primarily since it was a business trip, and I arrived late the first night, was out early the next day and then late home the second night, so I went straight to bed these nights. Day 2, I woke up and noticed bites on my feet and ankles and arm. Since I was in a humid place and in and outdoors the day before, I was concerned, but thought the bites I had where possibly from mosquitos or from a friend I had dinner with who had a dog. But the third night I came home, after a day of torrential rain, I went into the bathroom to my hang up my soggy shoes and noticed some black dots on my ankles, and went to dust what I thought was specks of mud off and ugh, the spots jumped. Then more jumped on and I removed them and rinsed them down the sink, only to stand there and over and over again rinsing them down the sink as they kept jumping on me. in dismay, I walked out onto the hardwood and back into the bathroom, assessing if it was as bad as I suspected, and sure enough, lots of fleas and then more kept jumping on me as I was standing there, mostly small from I suspect a recent hatching. It frankly was beyond gross and there was no way I could stay. I immediately left and communicated with the host since there was nothing, I would have been able to do to improve the situation except to leave. The host was apologetic, responsive, and we communicated to resolve.
In a perfect world the host would have refunded the whole stay since I ended up hugely out of pocket for a multiday hotel stay last minute.
Reading what it is like to be a host, I was sad to read the bitterness! I understand that you can end up with renters you don't like or who may be scammers - and I can understand it being upsetting. Hopefully you enjoy being a host and are working on creating an experience that benefits your guests and is fulfilling for you.
I share this experience, so you know that not all guests notice right away when something is off. And I honestly work to be a good guest, likely many others, so our reviews remain positive too. Also, as a guest, I and others take risks too and can lose out financially when pest or other issues arise. Honestly, no sincere guest wants to move or end a stay last minute if it can be avoided.
In my situation, I was able to afford moving accommodations, even though it was a big disruption and not what I had expected to spend, but some travelers who use the AirBnB experience to save money may not be as fortunate.
I would suggest that in some ways, as a host you have to deal with the possibility of pest exposure within a global travel business, as a potential cost of doing business, whether pet related or not. Also being a host means answering questions, even if you think they are annoying, because frankly being transparent and helpful are good traits as a host.
The AirBnB model works because there are primarily good hosts and good guests. I hope it continues to stay that way.