Ascaris suum, also known as the large roundworm of pig, is a parasitic nematode that causes ascariasis in pigs. While roundworms in pigs and humans are today considered as two species (A. suum and A. lumbricoides) with different hosts, cross-infection between humans and pigs is possible; some researchers have thus argued they are the same species.
In humans, often, no symptoms are presented with a minor A. lumbricoides infection, the inevitable consequence being the e.g. once a year passage of such clearly visible worm(s) on close inspection. In the case of bad infections symptoms commonly include bloody sputum, cough, fever, abdominal discomfort, intestinal ulcer(s), as well as a less commonly missed passing of the quite long worms. Ascariasis is the most common cause of Löffler’s syndrome worldwide. Accompanying pathological symptoms include pulmonary infiltration, eosinophilia (symptoms of the overabundance of eosinophils in the blood such as asthma and allergic reactions)