Capillariasis is the name of the disease caused by infection with
Capillaria species (referred to often as hairworms or threadworms), which are a type of internal parasite. When chickens are mildly to moderately infected, they can show a variety of nonspecific signs from general poor health, diarrhea, and eventually death. However during heavy infections, it starts to have a significant impact on their overall health. These birds will have a lower resistance against other infections and more severe symptoms, especially in younger poultry. Signs include unthriftiness, slow growth, weight loss, emaciation, reduced egg production, and death.
What are Capillaria species?
Adult
Capillaria are very thin, "threadlike" nematodes, that are approximately 1 cm (0.39 in) long. Their eggs, which can only be seen using a microscope, are barrel-shaped and have clear pugs on each pole. There are several different species of
Capillaria, each invades a specific region inside the chicken. Some species (
C. contorta and
C. annulata) will invade the crop and esophagus, causing thickening and inflammation of the mucus membranes. Others (
C. bursata, C. caudinflata, and
C. obsignata) target the lower intestinal tract, causing inflammation, hemorrhage, and erosion of the intestinal lining. When
Capillaria are present in high enough numbers, it can be fatal to the chicken.
Capillaria Life Cycle
The worms live inside infected birds, where they feed on various parts of their body and lay their eggs. Their microscopic eggs get passed through into the chicken's feces, contaminating the surrounding environment. The eggs are so microscopic, that you cannot see them with the naked eye. You need a microscope in order to identify their presence, hence why fecal tests are used as a great preventative tool. Other chickens in the flock will ingest the eggs when forging, eating, or drinking. Once ingested, the eggs hatch in the chicken and develop and feed on their crop, esophagus, small intestines, or ceca. Upon reaching adult age, the worms will then lay their eggs which gets passed through the chicken in their feces.
| Nematode species | Where Found | Intermediate Host | Definitive Hosts |
|---|
| Capillaria annuata | Esophagus, crop | Earthworm | Chicken, turkey, guinea fowl, partridge, pheasant, quail, goose, grouse |
| C. anatis | Small intestine, cecum, cloaca | None | Chicken, turkey, partridge, pheasant, goose, duck |
| C. bursata | Small intestine | Earthworm | Chicken, turkey, pheasant, goose |
| C. caudinflata | Small intestine | Earthworm | Chicken, turkey, guinea fowl, partridge, pheasant, quail, goose, grouse, duck, pigeon |
| C. contorta | Esophagus, crop, mouth | None or earthworm | Chicken, turkey, guinea fowl, partridge, pheasant, quail, duck |
| C. obsignata | Small intestine | None | Chicken, turkey, guinea fowl, quail, pigeon, goose |
