Mortality in Muscovy ducks (Cairina moschata) and domestic geese (Anser anser var. domestica) associated with natural infection with a highly pathogenic avian influenza virus of H7N1 subtype.

Among the 413 outbreaks of highly pathogenic avian influenza (HPAI) caused by a virus of the H7N1 subtype, which occurred in Italy during 1999 and 2000, an outbreak diagnosed in a backyard flock was characterized by mortality and nervous signs in ducks and geese. Dead geese (Anser anser var. domestica) and Muscovy ducks (Cairina moschata) were submitted to the laboratory for bacteriological, virological, histological and immunohistochemical investigations. Routine bacteriological tests resulted negative, while a HPAI virus of the H7N1 subtype was isolated from the geese. Pancreatic damage was observed in both the geese and the ducks, and the pancreas was also positive by immunohistochemistry for avian influenza in the geese. Histopathological lesions were observed in the central nervous system of both species, and this result was supported by positive immunohistochemical findings for the presence of the virus.