Capillaria

Capillaria spp.
Kingdom	Animalia
Phylum	Nematoda
Class	Adenophorea
Sub-class	Enoplia
Order	Trichurida
Super-family	Trichuroidea
Family	Trichinellidae
Genus	Capillaria
Species	Many

Overview

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

Capillaria spp. are similar to other members of the Trichuroidea superfamily such as Trichuris but with slight differences in morphology of the anterior and posterior ends. Although they are found in domestic mammals and some reptiles these species are of greatest importance in birds. The predilection sites vary between species and are not restricted to the gastrointestinal system. Important species include; C. annulata, C. anatis and C. contorta.

Identification

Capillaria are extremely thin, filamentous worms measuring 15-25mm long (males) and 35-80mm long (females). Males have a single spicule and many have a primitive bursa like structure. The eggs have bipolar plugs and thick shells, the size can vary between species.

Important Species

C. annulata

This species affects many species of wild birds as well as domesticated poultry and ducks. The earthworm is the intermediate host for this species, making it difficult to control. Young birds are more susceptible to the disease. Immune adults may be carriers. The predeliction site for this worm is the oesophagus of the bird where it will bury the anterior end into the mucosa causing inflammation. High levels can result in marked thickening of the oesophageal wall and can be fatal. The presence of these worms in low numbers may be a cause of ill thrift in production birds, though in high number emaciation can be seen. Clinical signs may appear very rapidly with heavy burdens, before the presence of eggs in the faeces, and so diagnosis is usually made on necropsy examination of the oesophagus and crop.

C. contorta

Also known as:

Eucoleus contorta

As with C. annulata this species is found in the oesophagus and crop of domestic poultry and many wild birds. Both the adults and the eggs of this species are smaller in size but the general morphology remains the same. The earthworm is normally the intermediate host but it is possible for this species to have a direct life cycle with the L1 embryonated egg as the infective stage. Clinical signs are rare with low levels of infection though they can be associated with a loss in productivity, high parasite burdens will result in emaciation and anaemia and can be fatal. The primary epidemiological concern with this parasite is its ability to have a direct life cycle and so birds kept indoors and away from the intermediate host may still become infected.

C. aerophila

Capillaria aerophila is associated with respiratory disease of cats and dogs. The worm can be found in the nasal passages, sinuses, trachea and bronchi. The presence of the worms causes a mild catarrhal inflammation and can cause coughing in dogs but not in all cases. In heavy infestation may cause obstruction of the lumen of airways and may develop into secondary bronchopneumonia