Dictyocaulus filaria

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Dictyocaulus filaria
Class Nematoda
Super-family Trichostrongyloidea
Genus Dictyocaulus
Species D. filaria

Also known as: Sheep lungworm


Sheep and goats.


D. filaria are of the superfamily Trichostrongyloidea. The adult worms are white, and the intestines can be clearly seen as a longitudinal dark bands running down the worm. The females are around 8cm in length, and the males are 6cm in length.

Life Cycle

The life cycle of D. filaria is very similar to that of Dictyocaulus viviparus. It is a direct life cycle, and the females are ovo-viviparous. The females lays eggs which contain mature larvae. The eggs hatch quickly, and the L3 larvae are ingested by the host. The larvae then travel to the mesenteric lymph nodes where they moult. They then travel to the lungs via the blood or lymphatic system.

The final transformations occur in the bronchioles, and the adults fully mature in the bronchi, causing bronchitis.

L1 larvae are then coughed and swallowed. The larvae enter the intestinal tract, and are passed out in the faeces.

The prepatent period of D. filaria is 4-5 weeks.



  • Grazing history
  • Clinical signs
  • Faecal examination (larval identification possible by examining head, e.g. Dictyocaulus filaria (knob) or tail, e.g. Muellerius (single spine), Protostrongylus (wavy, no spine) → prognosis)


  • Dictyocaulus filaria:
    • Difficult because outbreaks are unpredictable
    • PGE control measures are normally sufficient to prevent outbreaks of disease
    • Where these occur, remove and treat affected stock, replace with older immune sheep if necessary
    • A commercial vaccine was available in the Middle East, though its use (were it still available) would be uneconomic in the UK

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Dictyocaulus filaria publications


Taylor, M.A, Coop, R.L., Wall,R.L. (2007) Veterinary Parasitology Blackwell Publishing