A case of caseous lymphadenitis (CL) was detected in a native Korean goat without manifestation of superficial nodules but with pulmonary abscesses that were characterized microscopically by granulomatous inflammation consisting of a central necrotic region, peripheral fibrous capsule, and numerous cellular infiltrates with epithelioid macrophages, giant cells, and lymphocytes. Presence of Corynebacterium pseudotuberculosis was identified by using bacterial isolation and multiplex PCR. In addition, a 43% seropositivity to C. pseudotuberculosis was observed in goats from the same farm. This case highlights the risk of exposure of farmers to the causative agent and the urgent need for national monitoring for CL, a potential zoonotic.

Epizootic HPAIV, H5N6, and H5N8 infections produced severe loss in poultry and wild birds in the Republic of Korea from 2016 to 2017. But pathological lesions and antigen distribution of the novel HPAIV H5N6 clade 2.3.4.4 in natural cases have been rarely reported. Herein, we describe the pathological lesions and antigen localization in chickens (layer and Korean native), ducks, and Japanese quail naturally infected by HPAIV H5N6. Grossly, severe reddening, swelling, and some necrotic foci, which were similar to septicemia or viremia, were observed in skin and many visceral organs including trachea, lung, liver, spleen, and pancreas. Histopathologically, pulmonary congestion and edema, as well as necrotizing hepatitis, splenitis, pancreatitis, myocarditis, and encephalitis were observed. Immunohistochemically, numerous HPAIV antigens were detected in necrotic parenchymal cells and in blood vessels of the respiratory, lymphoid, digestive, urinary, nervous, and cardiovascular systems. The results indicate that HPAIV H5N6 spread to the entire body via blood and caused severe damage throughout the entire body. The HPAI H5N6 clade 2.3.4.4 virus was isolated from samples of all four cases.