This complex disease has been reported under various names such as helicopter disease, femoral head necrosis, brittle bone disease, infectious proventriculitis, pale bird syndrome, running and stunting disease.

Cause

The malabsorption syndrome appears to be a disease complex involving avian Reoviruses and other viral and bacterial agents which may affect the digestive system resulting in nutritional and deficiency signs and lesions.

Transmission

Only circumstantial evidence is present at the moment to indicate that the causal organism(s) may be vertically transmitted. Horizontal transmission also seems to play a role on infected sites.

Species affected

Chickens and possibly turkeys.

Clinical signs.

The disease is mainly observed in broiler flocks. Many affected broiler flocks have history of diarrhoea, beginning as early as a few days of age and lasting until 10-14 days of age. Light or dark brown, foamy droppings can be found with undigested feed particles. Several affected broilers in a flock may exhibit malpositioned feathers, especially on the wings. Early rickets with extreme paleness of legs and heads can be observed.

Encephalomalacia is also regularly found. At a later age (5-6 weeks) osteoporosis becomes clinically evident, frequently unilateral, causing the birds to limp. Later in age, an important effect is the delayed growth of the affected birds. Mortality is variable and in general as low as 4%.

Diagnosis

The clinical disease is characterized by one or more of the following lesions: enteritis with watery brown and foamy contents and the presence of undigested feed in the intestine. Mucosal and submucosal proventricular lesions. Pancreatic inflammatory infiltration with degenerative changes have been found. Osteoporosis and osteomyelitis, femoral head necrosis whereby the bone of the epiphysis of the femur is unusually soft.

Since the causal agent may differ, it is difficult to base a diagnosis on virus isolation or serology.

Treatment and control

Treatment is impossible. Vaccination against reovirus in the breeders helps to reduce problems in the progency. Strict hygienic and sanitary measures will reduce the incidence of the disease.