Viral arthritis also known as tenosynovitis is caused by reoviruses, and the clinical signs and manifestation of disease varies markedly depending on the pathogenicity and tropism (preferred tissue to infect) of the virus. Some can cause other disease syndromes such as early chick mortality and malabsorption syndrome, while others have shown severe systemic disease including pericarditis in chickens. Clinical signs include reduced growth and mobility, lameness, hock inflammation, swelling of the tendon sheaths and unthriftiness.
Viral arthritis is a classic manifestation of reovirus infection of chickens, and there are at least five serotypes of the virus. Morbidity is high but mortality is usually low. Transmission is by faecal contamination and birds can remain carriers for over 250 days. Diagnosis may be based on the history, lesions, IFA and rising antibody titre. Isolation may be readily achieved in in vitro cultures and serology may be by DID, FAT or Elisa. Subclinical infections (not associated with clinical disease signs) are common. Diagnosis is primarily to exclude mycoplasmosis, salmonellosis, Marek’s disease, Pasteurella and erysipelas as potential causative agents of the observed clinical signs.
Vaccination is ideally carried out by administration of a live vaccine in rear followed by an inactivated vaccine prior to lay. Most vaccines are based on strain 11/33. The virus is resistant to heat, ether, chloroform, pH and environmental factors, therefore, good biosecurity and hygeine practices and an all-in/all-out production system are the best preventative measures.