Pathological and immunohistochemical findings of natural highly pathogenic avian influenza infection in tufted ducks during 2010-2011 outbreaks in Japan

Abstract

In the winter of 2010-2011, an outbreak of highly pathogenic avian influenza virus (HPAIV) infection occurred in wild and domestic birds in Japan. Tufted ducks were found dead in an urban area of Toyota City, Koriyama, Fukushima Prefecture. Two tufted ducks were examined histopathologically, immunohistochemically and molecularly. Gross findings included marked dark-red clotted blood in the pectoral muscles and multifocal hemorrhages on the serous membranes. Microscopically, non-suppurative meningoencephalitis, multifocal to coalescing pancreatic necrosis and severe pulmonary congestion were observed. HPAIV antigen was detected in the malacic areas, neuronal, glial and ependymal cells, pulmonary capillary endothelial cells and epithelium of pulmonary bronchioles, necrotic pancreatic acini and degenerated cardiac myocytes. The HPAIV isolate was genetically classified into clade 2.3.2.1 group A. The broad distribution of virus antigen in brain and pulmonary tissues associated with HPAIV spontaneous infection in tufted ducks might be useful in understanding its pathogenesis in nature.

Fig. 1.

Gross and histopathological findings of HPAIV in tufted ducks. Lesions were characterized grossly by (a) marked dark-red clotted blood in the pectoral muscles and (b) multifocal hemorrhages on the serosal surface of the liver and pericardium and (c) in the lungs. (d) The histopathological findings in brain of tufted ducks were non-suppurative meningoencephalitis characterized by perivascular mononuclear cell cuffing, multifocal neuronal degeneration and gliosis.

Fig. 2.

Immunohistochemical detection of avian influenza antigen in tufted ducks in (a) subcortical multifocal liquefactive necrosis and (b) ependymal, degenerated neurons and glial cells of the brain, (c) the pulmonary endothelium of the alveolar capillary, (d) epithelial cells of the parabronchus and atrium, (e) pancreatic acini and (f) focal degenerated cardiac myocytes as well as in (g) lymphocytic infiltration in lamina propria of the intestine in positive control chicken, but not in (h) brain of negative control chicken (ABC immunoperoxidase technique, counterstained with Mayer’s hematoxylin).