Atlas of livestock parasites
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Ascaris suum



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Nematode (roundworm)

"Large roundworm"

Description:  Ascaris suum is a large, white worm, 15 to 40 cm long as an adult.

Life Cycle: Female worms in the small intestine each produce up to a million eggs per day. These eggs are very resistant to drying, heat, and freezing and may last for years in the environment. Larvae develop to infective second stage within the egg in as little as 10 days with favorable warmth. These infective eggs contaminate the soil, food, water, dust, and pastures of many swine farms. After ingestion, the eggs hatch, releasing larvae which penetrate the small intestine and are carried in the blood to the liver. The larvae migrate through the liver parenchyma, molt to L3 and migrate to the lungs. The larvae break into the alveoli of the lungs, ascend up the bronchi and trachea, molt to L4, reach the pharynx and are swallowed and go to the small intestine. The mature worms begin to lay eggs two months after infection. The adults live on the intestinal contents.

Distribution:  Common worldwide.

Significance:  Ascaris is the most important swine endoparasite, causing extensive economic losses due to morbidity, mortality, and condemnation of livers.

Clinical features:
 Adult ascarids compete with swine for food and can markedly reduce feed efficiency. Heavy infections cause intestinal irritation, with mucus production, diarrhea, and weight loss. Sometimes the adult worms "ball up," blocking the intestine, which may burst and cause peritonitis. Damage caused by migrating larvae is of principal importance. Migration through the liver causes the white scarlike "milk spots," which are the major reason for swine liver condemnations in packing plants. Massive migration through the lungs causes extensive damage and secondary infections. Severe infections may cause death. Repeated infections, accompanied by lung hemorrhage, edema, and emphysema, result in an asthma-like condition called "thumps" or "heaves."

Diagnosis:  Fecal examination for eggs or by the presence of the worms found in the small intestine at necropsy.

Control: Are planned to prevent ingestion of eggs by pigs until they go to market. Before sows are introduced to farrowing quarters, the pregnant animals are wormed and washed, and the quarters are scrubbed with lye.


Ascaris adult
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Ascaris: eggs
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Ascaris: in intestine
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Ascaris: milk spots
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