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.
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
Pathogenesis and clinical signs
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
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.