Need info on parasites and protozoa...

Hi, I wanted to learn more about parasite and protozoa infections in snakes. How common are they in wc and cb animals? What are the symptoms, treatments, safety and cost of treatments? Also how much would a fecal be for an animal you can't get a stool sample from? What does everyone else do with your snake in regards to prevention or parasites, besides quarantine?

I'm still new to all of this so I want to educate myself a bit more. I want to get a fecal done on two of the girls and I want to get some info first. They're both adult wc ball pythons, one i got as a wc 10 years ago and the other I got about 6 months ago. The newer girl has been eating but not gaining much weight compared to everyone else and i doubt she had much parasite treatment before i bought her. The other girl I'm just gonna do one just in case. She def doesn't have a weight issue but she's been a pain in the butt feeder for ten years, she only eats two months out of the year since the day I bought her. She'll pig out june and july and stop the first day of august without fail. Her weight is great for how little she eats but I just want to check her anyway and make sure nothing is stressing her, maybe I can get her to eat more for once lol.