worms and microscope dangerous bad parasites. ascarid, helminth pinworm threadworm

anatomy animal ascariasis ascarid ascaris biology body care danger dangerous design digestive disease evil flatworm health helminth hookworm human hygiene icon illness illustration infecting infection intestinal intestine isolated larva life medical medicine microscope nature nematode parasite parasitic parasitology pinworm roundworm science sign simple small symbol tapeworm tract vector white worm