common roundworms in sheep belong to 3 genera Haemonchus - Ostertagia - Trichostrongylus

OSTERTAGIA - University of Sidney

The life cycle of a typical stomach worm.
This page was last updated on: January 20, 2008
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Small Brown Stomach Worm
Ostertagia Circumcinta
Invades the wall of the sheep's fourth stomach (abomassum) causing scouring, weight loss and even death
Sheep develop strong immunity to this worm.
Late pregnant and lactating ewes are main source of pasture infection.
Weaner sheep have lowest immunity.

Ivomec, Controls 14 types of sheep roundworms, all larval stages of nasal bots, and lungworms.
Safe-Guard, an excellent tapeworm dewormer.
Tramisol, Oblets hit major sheep stomach worms, intestinal worms and lungworms.
Valbazen, a broad spectrum anthelmintic for sheep flukes, tapeworms, stomach worms, hookworms and more
Internal parasites are the #1 health problem affecting small ruminants. Sheep and goats are more susceptible to internal parasites than other livestock, due to their grazing behavior and poor immunity

Ostertagia Circumcinta, better known as the small brown stomach worm. It burrows itself into the lining of the abomassum. But instead of causing blood and protein loss, it causes digestive disturbances such as diarrhea and weight loss. Both the barber pole worm and brown stomach worm can cause substantial death losses in goat herds, if left unchecked.

Worm larvae (eggs) love warm, moist conditions, but can survive winter by going into a dormant or arrested state and not resuming their life cycle until the spring when environmental conditions have improved.
Information above came from the article Integrated Parasite Control (IPM) in Small Ruminants
by Susan Schoenian - Area Agent, Sheep and Goats University of Maryland College Park