Ascaridia - Poultry
| Scientific Classification | |
|---|---|
| Kingdom | Metazoa |
| Phylum | Nematoda |
| Class | Secernentea |
| Sub-class | Rhabditia |
| Order | Ascaridida |
| Family | Ascaridiidae |
| Genus | Ascaridia |
Also known as: Torovirus —Torovirus infections — Berne virus— BEV — Breda virus— BRV— Bovine torovirus— BoTV— diarrhea in calves— Equine torovirus—Ascaridosis—Ascarids—Ascaridia.
Introduction
A. galli, A. dissimilis and A. columbae are nematodes that occur in the small intestine of poultry. They can affect the reproductive system and in heavy infections, cause partial or total obstruction of the duodenum/jejunum. Adult A. galli are semi-transparent, have three prominent lips in their oral openings and are the biggest nematodes found in poultry. Females range from 72 to 116 mm in length and their reproductive organ opens in the middle of the body. Their eggs are oval, with smooth shells and measure 73-92 by 45-57 µm and distinguished from H. gallinarum eggs by their slightly smaller and parallel sides (Soulsby, 1982). Males vary from 51 to 76 mm in length and they have pre-anal suckers and two equal spicules of 1-2.4 mm long. Compared to A. galli, A. dissimilis is slightly bigger and A. columbae is slightly smaller.
Signalment
The host for A. galli is chickens, but it can also infect turkeys, geese, guinea fowl and wild birds. A. dissimilis can infect turkeys and A. columbae is found in pigeons.
Clinical signs
Ascarids cause anorexia, diarrhoea, dehydration, stunted growth, unthriftiness, drooping wings, ruffled feathers, weight loss, dullness, lethargy and misshapened and soft thin shelled eggs in poultry. Clinical signs are more pronounced in chickens up to 3 months of age, after which the worm burden normally decreases. Birds will have blood loss, reduced blood sugar and distended ureters with urates.
Distribution
Worldwide
Epidemiology
Infected chickens pass A.galli eggs in their faeces and the larvae develop inside the egg until it reaches its infective stage (L3) within 10-20 days or more, depending on environmental temperature and humidity. The embryonated egg can survive a winter with moderate frost and remain infective in deep litter systems for years depending on the temperature, humidity, pH and ammonium concentration. Ascaridia galli has a direct lifecycle and it is complete when a new host (another chicken) ingests the infective embryonated eggs (L3) from contaminated water or feed. Three layers around the egg protects the larvae until it reaches the duodenum/ jejunum, where they hatch within 24hrs and enter the histotropic phase where they embed themselves into the mucosal layer of the intestine. The more eggs are present the longer the histotropic phase lasts. The length of this before the final maturation has been reported to be between 3 to 54 days (Herd and McNaught, 1975). The prepatent period varies from 5 to 8 weeks. Adult A. galli worms may migrate through the lumina of the large intestine and cloaca and end up in the oviduct, where they can be incorporated into the hen’s egg. Occasionally, earthworms can ingest A. galli eggs and ascarids are transmitted when the chicken ingests the worm. The life cycles of A. dissimilis and A. columbae are also direct and A. dissimilis may migrate through the liver (Norton et al., 1999).
Diagnosis
Ascaridia can be diagnosed by the above clinical, faecal examination or by post-mortem (PM). Evidence of enteritis/haemorrhagic enteritis can be seen on PM; as large numbers of larvae in the histotropic phase can cause extensive damage to the glandular epithelium. Adhesion of the mucosal villi can also be noted as a result of the proliferation of mucous-secretory cells. Adult worms can also cause damage to the epithelia as a result of pressure atrophy of the villi, causing occasional necrosis of the mucosal layer. In chronic infections the intestinal wall can become distended as muscle tone is lost.