Trichinelloidea

PARASITES NEMATODES

Trichuris ovis from sheep faeces - Joaquim Castellà Veterinary Parasitology Universitat Autònoma de Barcelona

Trichuris ovis in caecum - Supplied by Biomed Image Archive

Trichuris vulpis - Courtesy of the Laboratory of Parasitology, University of Pennsylvania School of Veterinary Medicine

The common feature of members of this group is that the oesophagus is a column of doughnut-shaped cells. They are only distantly related to the other nematode groups and so drugs developed primarily for controlling strongyle and ascarid worms are often less effective against these.

There are just three genera of veterinary importance:

1) Trichuris (the whipworms)

2) Capillaria

3) Trichinella

Trichuris Species

• The whipworms have a stout posterior end and a long narrow neck, which is superficially inserted into the caecal mucosa. *Eggs are brown, barrel-shaped, with a plug at either end, and can survive for up to 12years.
• The infective stage is the embryonated egg.
• The life-cycle is direct.
• After the egg is swallowed, the larva initially forms a mucosal nodule before emerging into the lumen.

Capillaria

• Similar to Trichuris, but the difference between anterior and posterior ends of the body is not so pronounced.
• Some species have direct life-cycles, others use intermediate or transport hosts.
• Species have different predilection sites.
• Of greatest importance in birds, species do occur in the urinary bladder and liver of cats and dogs.

Trichinella

• This is known as the "worm that thinks its a virus".
• It is a unique genus, and an important zoonosis.

Trichuris

• Capillaria aerophila in respiratory disease of cats and dogs
• Trichinella in myositis