Could you post the lab report so we can see the exact wording they use? Did you have the complete enteric panel?
Most parasite drugs and herbs target a group of similar parasites - similar protozoa, roundworms, flatworms, etc.
parasites in general, especially intestinal parasites, will live where ever the environment sustains their growth so many parasites that have one main host can live in other animals. Often this alters their life cycle but they can persist and cause problems. Hulda Clark wrote that some parasites can only live in or infect humans when there are specific pollutants present in the persons body. In many cases identifying the pollutant and detoxing then avoiding all sources of that pollutant was part of the cure.