Brown Stomach Worm
Ostertagia ostertagi
The infamous Ostertagia is the most economically important parasite in cattle. This worm also has a unique ability to penetrate the lining of the true stomach and become dormant, or inhibited, so that it can survive during weather that’s too cold or too hot. When conditions improve, the larvae can emerge all at once and do serious damage to the lining of the stomach.