Large-mouthed bowel worm

(Chabertia ovina)

Chabertia ovina is a large (up to 20 mm) stout white worm and so named because of its large bell-shaped buccal (mouth) capsule that is bent ventrally. It is found in cattle pastured in the cool climate winter rainfall areas of southern Australia and is only likely to be present in cattle that are co-grazed with sheep and goats.

The adult female lays around 5,000 eggs per day.

Further ecological information on worms and their control:

• Roundworm life cycle and life stages
• Large-mouthed bowel worms follow the basic roundworm life cycle but the infective larvae undergo a tissue phase in the wall of the small intestine before moving as fourth stage larvae into the caecum and finally, as adults into the large intestine. The pre-patent period is about 49 days.
• Climate factors contributing to paddock contamination with worms
• Pasture management to reduce exposure to worms, alternate grazing and co-grazing
• Cost of roundworms

Location in host

Worms are found in the coiled region of the large intestine (colon).

Signs

C. ovina is non-pathogenic to cattle and clinical disease is seldom seen.

Signs of worms

Figure 1. Section of the colon containing large-mouthed bowel worm. Image courtesy of Nick Sangster

Diagnosis

The eggs are found on a worm egg count (WEC) when analysing dung samples for other roundworm eggs.

Figure 2. A large mouthed worm, Chabertia sp. (colour is due to preservation). Image courtesy of Mukund Madhav

Figure 3. Anterior end of a large mouthed bowel worm, Chabertia ovina, showing the large bell-shaped mouth. Image courtesy of Lindsay Jue Sue and Constantin Constantinoiu