OSTERTAGIA

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NAMES

Ostertagia circumcincta (Alternative genus name Telodorsagia)

HOSTS

sheep, goats

SITE

Abomasum

LIFE CYCLE

Direct

PP: 20 days

MORPHOLOGY

Head - both sexes
Vulval flap
Female tail
Male tail
Head of both sexes
Vulval flap
Female tail
Male tail

APPEARANCE

Small (up to 10 mm), red-brown worms just visible on the lining of the abomasum.

OTHER SPECIES

O. trifurcata - Tail
O. trifurcata - Tail

DISTRIBUTION

Click here for the map of Distribution:

    Ostertagia Distribution

CONDITIONS

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.

DISEASE

Most commonly cause production-loss in the absence of obvious disease. Diseased sheep have reduced appetite and protein loss into the gut.

EFFECTS

  1. Ostertagia damage the lining of the stomach as they mature from larvae to adult worms.
  2. Sheep with heavy infections of Ostertagia rapidly lose condition, develop profuse scours and may die. Animals with fewer worms are unthrifty and daggy. Mixed infections of Ostertagia and Trichostrongylus are more lethal than infection with only one of the worms.
  3. In animals that die from heavy infections of Ostertagia brown, entwined masses of worms are found on the lining of the stomach. The lining is also covered with confluent, whitish nodules and is thickened and red. The carcase is emaciated.
  4. Post mortem of animals with lighter infections will reveal smaller numbers of worms and nodules.

DIAGNOSIS

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.

EGG