Overview of Rotaviral Infections in Chickens, Turkeys, and Pheasants
Rotaviral infections are characterized by enteritis and diarrhea in young birds, but chickens have been infected without showing clinical signs.
Avian rotaviruses consist of four distinct serotypes (A–D). Group A rotaviruses share a common group antigen with mammalian rotaviruses. Group D rotaviruses have been identified only in avian species. The relationships of the other two avian serotypes to mammalian serotypes have not been established. Transmission is horizontally by the oral route. Egg transmission has not been reported.
Early signs of diarrhea (wet litter), depression, and poor or abnormal appetite can be seen 2–5 days after infection. Dehydration occurs rapidly, and mortality can be as high as 30%–50% in pheasants but is lower in turkeys and chickens. The survivors appear healthy but smaller than normal. Lesions consist of dilated intestines filled with yellowish, frothy, watery contents. Often, the carcass is dehydrated. Mortality is variable and is usually due to dehydration and emaciation or secondary bacterial infections.
Early diarrhea and inappetence that sometimes end with death are indicative but not pathognomonic of rotaviral infection. Fecal samples or intestinal contents can be examined by electron microscopy with negative staining, either directly or after ultracentrifugation. Numerous rotaviral particles ~70 nm in diameter, with double-shelled capsids, can be seen and are distinguishable from reovirus by their more sharply defined outer edges. For viral isolation in chicken-embryo liver cells or chick kidney cells, fecal material must be treated with trypsin. Isolated rotaviruses belong mostly to serotype A and, in general, do not cause cytopathic effects on primary isolation. The presence of virus can be demonstrated 2–3 days after inoculation by immunofluorescent staining. Reverse transcriptase PCR is currently used to detect the virus in gut contents.
No commercial vaccines are available. Thorough cleaning and disinfection of infected houses is advisable to limit infection. There is no specific treatment.