Cysts and motile forms are found in feces. Hogs harbor commonly Balantidium coli. Infection of men is caused by contaminated food and water. Trematodes like the flukes . Cestodes which are the tapeworms .
Bacteria can multiply in the human body almost indefinitely.
Worm parasites do not multiply in the human host, they usually need to pass through stages in the human host and then they have to undergo other stages in one or more animals, im soil or water. Some persons may harbor only few worm parasites, the infestation remains subclinical and symptomless. However with repeated exposures a massive infestation takes place and illness comes up. Ancylostoma duodenale and Necator americanus The infestation with both worms are alike and no laboratory attempt is made to differentiate among them, reporting as larvae of ancylostomideans. The hookworms are a quarter to halve an inch long.