Ostertagia circumcincta (Alternative genus name Telodorsagia)
PP: 20 days
Small (up to 10 mm), red-brown worms just visible on the lining of the abomasum.
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L3 are resilient, able to survive a range of climatic conditions including freezing on pasture and relatively dry conditions. Also commonly arrest in the sheep.
Most commonly cause production-loss in the absence of obvious disease. Diseased sheep have reduced appetite and protein loss into the gut.
Identification of worms at postmortem. Recovery of eggs from faeces, but these are similar to those of other nematodes. Laboratory measurement of sheep plasma pepsinogen.