It takes about four days for larvae to reach the liver, nine days to reach the lungs and 15 days to complete the trip to the intestine. Worms grow to egg-laying adults in about 60 days. Clinical signs of roundworm infestation are primarily associated with larval migration through the lungs. Pigs have a dry nonproductive cough, loss of appetite and weight, rough hair coat, increased temperature, and an increased rate of respiration accompanied by thumping. 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.