There are zoonotic infections which means pathogens that can cross from animal to human. Unfortunately there are so many species that could be a possibility. IMO it is best to treat with a wide spectrum approach, and by that I mean use a multi prong approach say for roundworm which would include many products rather than relying on a single remedy.
I use this approach and with trial and error, I got it to work. You have to place close attention and observe.
Something helpful is to look at the window of opportunity which means there should be a 7 to 10 day window when you know something is working. If you do not see anything positive after this time then move on to the next set of remedies.
If you see some improvement during this period but a reversal happens then resistance may be a factor. The only proven remedies for resistance are taking hemp seed oil (this is not marijuan oil but hemp oil, something like Nutiva) and goldenseal leaf (not root). These can lock up the resistance and allow the other things to do their job.