Ascaris is a nematode genus of parasitic worms known as the "small intestinal roundworms".

[1] One species, Ascaris lumbricoides, affects humans and causes the disease ascariasis.

[2] A. lumbricoides is the largest intestinal roundworm and is the most common helminth infection of humans worldwide.

As part of the parasite defense strategy, Ascaris roundworms secrete a series of inhibitors to target digestive and immune-related host proteases, which include pepsin, trypsin, chymotrypsin/elastase, cathepsins, and metallocarboxypeptidases (MCPs).

[9] The morphologically similar Ascaris suum was described from pigs by Johann August Ephraim Goeze in 1782.