An epidemic of fatal hepatic necrosis of viral origin in racing pigeons (Columba livia).

In October 1992, a new disease characterised by acute death in racing pigeons of all ages was noted among the Belgian pigeon population. Clinical symptoms were minimal since affected birds usually died within 24 h. Mortality in pigeon lofts usually amounted to 30%. The most typical necropsy finding was a yellow, pale and swollen liver. Histological and cytological examinations revealed extensive focal or diffuse hepatic necrosis and the presence of eosinophilic or amphophilic nuclear inclusion bodies. This hepatic necrosis of viral origin was diagnosed in 151 (15%) of 988 submissions of pigeons at our Institute in 1993 and 1994. Oral and intramuscular inoculation of pigeons with a bacteria-free homogenate prepared from the liver of pigeons that died from the disease did not result in clinical signs. However, when similar inoculations were done in pigeons previously treated orally with dexamethasone, pigeons died very suddenly within 4-5 days of inoculation. Necropsy findings in experimentally infected pigeons were identical to those observed in naturally occurring cases. Electron microscopic examination of the liver of inoculated pigeons showed the presence of numerous adenovirus-like particles inside nuclei of hepatocytes. The virus could not be cultured in the allantoic cavity or on the chorioallantoic membrane of embryonated chicken eggs. Clinical signs and lesions described here are clearly different from adenovirus enteritis in young pigeons abundantly described since 1976.