Also known as Viral tenosynovitis
Viral arthritis (Viral tenosynovitis) occurs worldwide in all poultry species between 3-30 weeks. Broilers develop problems from 5-8 weeks and breeder pullets at 10-18 weeks. It is caused by a double stranded RNA reovirus.
- Causes of Viral arthritis >
- Effects of Viral arthritis >
- Diagnosis of Viral arthritis >
- Treatment & Control of Viral arthritis >
Causes of Viral arthritis
All species of bird from 3-30 weeks old, mostly broilers and broiler breeders, are susceptible to this chronic to debilitating disease. Broilers develop problems from 5-8 weeks and breeder pullets at 10-18 weeks of age. The disease is caused by a reovirus (respiratory, enteric, orphan).
Mode of transmission
Spread laterally from bird to bird or vertically from hen to offspring. Faecal to oral or via respiratory tract transmission can also occur.
Special note
It commonly causes downgrading and trimming in broilers and culling in breeders.
Effects of Viral arthritis
Incubation period of 9-13 days. Birds are down on the hocks, have stunted growth, reluctant to move and have an uneven gait. Swollen tendons above and below the hocks and ruptured gastrocnemius tendon is also seen.
Postmortem lesions
Bilateral swelling of tendons (digital flexor and metatarsal extensor) is diagnostic. There is an increase in clear, thick fluid in joints and swelling of the footpad, straw coloured or blood-tinged exudate can be seen in lesions.
Ruptured tendons, haemorrhaging of synovial membrane, erosion of cartilage of distal tibiotarsus can also occur. The condyles (joint capsule) may also be involved.
Diagnosis of Viral arthritis
Isolation of virus from lesions on CAM of inoculated embryos and serologic test for VA antibodies (VN or ELISA) are of limited use because birds are routinely infected with non-pathogenic reoviruses.
Histopathology, reveals oedema, coagulation necrosis, heterophil accumulation and perivascular infiltration. Hypertrophy and hyperplasia of synovial cells, infiltration of lymphyocytes, macrophages and reticular cells are also evident.
VA causes excessive or clear straw coloured fluid; Mycoplasma synoviae causes honey coloured fluid and Staphylococcus produces thick white fluid in swollen joints.
Gross and microscopic lesions are diagnostic.
Ruptured gastrocnemius tendon is characteristic.
Treatment & Control of Viral arthritis
Prevention
Vaccination of parent stocks no later than 20 weeks of age with the S1133 virus strain. This is usually given at 2 weeks (SQ or water) and between 6-10 weeks (water) with live vaccine. Killed virus is given at 18 weeks and possibly again at 40 weeks by SQ injection.
Re-vaccination by drinking water is not allowed in most countries outside the US. SQ is common.
Attenuated live vaccine diluted by 1/3 at 1 day with a full dose of HVT for broilers in problem areas or by coarse spray at one day of age with a full dose. Boosting at 7-10 days by spray or water is sometimes done. This is not allowed is most countries outside the US.
Treatment
None. Antibodies are used to prevent secondary Staph infections.
