If you look at the protocols for cleaning up autistic kids and parasites, the probiotics are added after the parasites are gone.
My favorite probiotic is kim-chi. I use it in place of salsa. Sauerkraut is next. Love fermented salsa but I can't find it organic and I am too lazy to make it. There are other fermented veggies on the market. You want as much diversity as possible in your gut flora. So eat as many different 'cultured' or fermented foods as possible. Kefir, yogurt, some cheeses, kombucha. Read Dr. Perlmutter's book: Brainmaker.

I agree with the other poster - most commercial probiotics are transient meaning they have to be resupplied vs becoming a permanent part of the gut biotics. Prebiotics are a better choice IMO.

The other problem w/ probiotics is that there are hundreds of species of healthy organisms while the probiotics only supply maybe 10 strains though you could argue that bifidus and lacto strains are major strains that colonize the large and small intestines respectively. I am sure they can be used at times that could be helpful. Many people swear by kefir.

Probiotics may increase the inflammatory immune responses leading to more problems.

There is also a large problem with defining parasites which I see often. There are a number of things that can inhabit the gut including rogue bacteria, yeast/fungal strains (not just candida), viruses and parasites. Each of these would require a different strategy.

The term parasite is thrown around without much definition. Are people talking about worms, flukes or protozoa? All are parasites but there is a big difference between them. Protocols are completely different for each and protocols can vary for protozoa. Sorry to throw a lot of things at you. Trial and error is the best course to follow.