They can cause both mental and physical retardation. Found in herbivores throughout the world. Grazing areas are constantly reinfected. Human infection of S. steroralis is acquired by skin penetration of the filariform larvae from the soil. Over 40 million people have acquired food borne trematode infections.
Infections occur from Raw fish or uncooked water plants.
Carried by dogs, cats and other fish eating animals. Light infestations are asymptomatic, although lung lesions may be noted on X-ray examination. Sometimes mistaken for cancer of the lungs. Eventually chronic cough develops with blood tinged sputum and vague chest pains. Estimates are 22 million people worldwide have these.