Both young and adult worms cause damage. Young worms destroy liver tissue, causing abscesses and scars. In the lungs they penetrate blood vessels, destroy tissue and plug smaller air passages. Damage to the integrity of the lung tissue predisposes pigs to pneumonia. Adult worms in the intestine rob the pig of food, block the gut and excrete substances which interfere with digestion.
Diagnosis is made by microscopic identification of eggs in the feces.
Adult worms in the intestine and scars in the liver are seen on postmortem examination. Whipworms Trichuris suis , is called the whipworm because it is shaped like a whip. It has one of the simplest life cycles known. Eggs are laid in the large intestine and pass from the body in manure. They develop into infective larvae in 21 days.