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.

The influenza virus is an important respiratory risk affecting humans, and effective treatments are needed. Some oriental medicines are currently applied for treatment of common colds as well as influenza infection. Previous studies have reported that the therapeutic properties of MA-128 are effective for treatment of psoriasis antiasthmatic and atopic dermatitis. In this study, we investigated the therapeutic properties of the novel herbal medicine, MA-128, for treatment of influenza virus infection by oral administration. MA-128 is an active natural biological compound from herbal-marine origin. The results showed that oral administration of MA-128 in mice could confer a survival benefit against Type A influenza virus infection. Daily oral administration of MA-128 resulted in delayed death in infected mice for three days against mouse adapted H3N2 (A/Philippines/2/82). However, it protected more than 60% of mice from lethal infection of 2009 pandemic H1N1 (A/Korea/CJ01/2009) influenza virus. In addition, lung viral titers were significantly reduced at seven days post infection (~100 times) compared with mock-treated mice and viruses were cleared at 9 dpi only in the MA-128 treated groups. This study demonstrated the potential of the novel herbal medicine, MA-128, as an herbal remedy against influenza A viruses.

Since there had been the first human outbreak of novel influenza A/H1N1 in Mexico, it has become pandemic throughout the world. In the Republic of Korea, the first human case was on May, 2009 and National Veterinary Research and Quarantine Service (NVRQS) has started monitoring novel influenza A/H1N1 on domestic swine farms. The first positive case was detected on 14, Dec, 2009 and until now, we have had total 17 positive cases. From the first case, we did epidemiological investigation on introduction and transmission of virus to pigs. We have concluded that virus had been introduced from humans to pigs, possibly from October to November, 2009 in our country. There were direct and indirect factors including the vehicles transporting veterinary medicine, feed, etc. related to transmission of virus from farm to farm. However, breeding pigs seem to be extrinsic to transmitting factors. Upon the epidemiological investigation, the off-limits of visitors to farms and the disinfection is thought to be critical for blocking the introduction and transmission of novel influenza A/H1N1. In addition, collecting and analyzing the genetic informations of influenza virus is important for predicting and handling the new pandemic influenza in the future.