These are small (~10mm) reddish brown worms found in the abomasum of
ruminants. On a global basis they are the major cause of parasitic gastritis
(Ostertagiosis) of ruminants in temperate climates.
The following table lists the three major species.
|sheep and goats
||sheep and goats
Other, less common species include O. lyrata, and O. kolchida in
cattle plus O. leptospicularis found in cattle, sheep and goats.
Ostertagia species are found throughout temperate and subtropical areas of the world.
The cattle species, Ostertagia ostertagi is particularly important in temperate
areas wherever cattle are raised.
Adult worms are small (approximately 1 cm long) and brownish in color. They
are difficult to see at necropsy unless they are present in large numbers (thousands). All
parasitic larval stages are found in the gastric glands of the abomasum which must be
digested in order to release the larvae for observation with a microscope.
A buccal cavity is present, although tiny, as shown by the linked images from light microscopy and scanning
The spicules of males are fairly similar in size and shape but are quite
distinguishable from spicules of males in other abomasal nematodes
(Trichostrongylus axei and Haemonchus).