Reovirus

The word “reovirus” is derived from the details surrounding its discovery:

R = isolated from the human respiratory tract
E = also found in the enteric tract
O = considered an “orphan” virus since it was not associated with disease

Reoviruses are widespread in nature. First isolated from chickens in the 1950s, avian reoviruses have been associated with numerous conditions including viral arthritis/tenosynovitis, malabsorption syndrome, stunting and runting syndromes, enteric disease, immunosuppression, and respiratory disease. Recently, there have been reports of reoviruses from chickens exhibiting neurological signs, including tremors, twitches and a lack of coordination.

Affected birds are small, have poor feed conversion, and may experience diarrhea, which could adversely affect the litter. Though mortality is usually low, reoviruses can affect a large number of birds in the flock. Some of the symptoms seen are viral arthritis with joint swelling, thickened or ruptured tendons and lameness. These are major causes for concern among poultry producers because of the economic implications of these conditions. Reoviruses are seen primarily in broiler chickens, but have also been reported in layers and in turkeys.

Vaccination programs in breeder birds have helped to reduce the incidence of reoviruses in subsequent generations. Strict biosecurity procedures can also effectively reduce the incidence of reoviruses on commercial poultry flocks.

Unfortunately, a new form of reovirus, called enteric reovirus strain (ERS), is emerging and causing worry among producers. Generally found in broilers with malabsorption syndrome or wet litter, ERS leads to high mortality in young birds and significant production losses in those that survive. A vaccine for ERS is currently being studied.