Some of us carry quite a variety of parasites although only a few of the organisms are present in large numbers. People who live in ares with poor sanitation carry heavier infestations than people in more developed areas, tho most of the parasites are the same. Hulda Clark wrote that a person with good immunity and healthy digestion resist parasites more efficiently.
In my case my immunity and digestive system was compromised by autoimmune gluten sensitivity (Celiac Disease) and when tested on a Bioresonance machine by an ND she found over 100 different parasites. This was very unusual, most of the people the ND tested had less than 10 parasites. One of the ND's patients, a person who worked with horses, had 8 parasites including several horse parasites.