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The only species of importance in domestic animals is Hyostrongylus rubidus , commonly called the "red stomach worm" of pigs. It is a slender worm, 5-10mm in length. The image on the right shows fresh specimens in the stomach at necropsy. Its reddish color when fresh has led to the assumption that the worm is an active blood feeder although this claim is disputed because its parasitic phase in the host is very similar to Ostertagia species. It is a common nematode of adult swine, with access to pasture and has a world wide distribution in areas with temperate climates.

Life cycle

The life cycle is similar to other members of the family Trichostrongylidae. The prepatent period is approximately 3 weeks.
Infected animals pass "strongyle type eggs" which cannot be distinguished morphologically from Oesophagostomum dentatum and Trichostrongylus axei except by larval cultivation. Seasonal hypobiosis  is an important feature of the life cycle in temperate areas of the world.

Because of the free-living larval requirements, infection is mostly seen in pigs with access to pasture. However, transmission has been recorded in pigs raised totally in confinement.

Pathogenesis and clinical signs

Sw010sm.gif (30482 bytes)Pathogenic effects of Hyostrongylus infections are similar to Ostertagia in cattle. It causes a hemorrhagic gastritis and usually presents as a chronic wasting disease with anemia, loss of condition, anorexia and sometimes diarrhea. Since L3s invade the gastric glands and emerge as immature adults as in ostertagiosis, parietal cells are replaced by proliferating immature cells that produce nodules (as shown in the accompanying image) similar to those in ostertagiosis.

Heavy infections may produce ulceration of the gastric mucosa with excessive bleeding from ruptured blood vessels giving rise to a hemorrhagic gastritis. It seems likely that the reddish appearance of the worms may be due to passive ingestion of hemorrhagic stomach contents during feeding by adults.


Parásitos y enfermedades parasitarias de los animales domésticos
Dr. Colin Johnstone (autor principal)
Derechos de copia © Universidad de Pennsylvania