Meat ducks and laying ducks affected by highly pathogenic avian influenza usually show a variety of clinical symptoms. The clinical symptoms of commercial meat ducks and small-bodied egg ducks are sudden onset of symptoms, which can be seen in a short period of time, such as loss of appetite, sudden rise in body temperature, high depression, respiratory distress, coughing, sneezing, tearing, and dysentery. Neurological symptoms appear in the later stage, manifested by the neck twisting backward, and the sick ducks mostly die acutely, with a mortality rate of more than 90% within a few days. Adult meat breeder ducks infected with avian influenza virus can develop the disease in a relatively short period of time, and the above symptoms of its influenza disease are obvious, and the egg production rate drops to zero within 2 to 3 days. However, the mortality rate of sick ducks is only about 1.0% or less. The sick duck can fully recover in about 30 days, and its egg production rate cannot be restored to its original level, and can only reach a maximum of 50% to 60%, and a larger amount of deformed eggs that cannot be used for hatching. At this time, the feeding value has been very low, generally can not get economic income, but often serious losses. Therefore, when meat breeding ducks are found to be suffering from avian influenza epidemic, they should be actively reported to the relevant government departments and actively cooperate with the decisive action taken by the government in order to prevent the spread of the epidemic.

Pathological autopsy showed that the sick ducks suffering from avian influenza had scattered hemorrhages in the chest muscles and abdominal fat, respiratory distress, pulmonary edema and hemorrhage, hemorrhages in the heart, liver and kidneys, swollen and hemorrhagic adenogastric papillae, hemorrhages in the subcorneal layer of the muscular gastric horny membrane and duodenum, and substantial changes and necrotic foci in the pancreas, kidneys, spleen and liver.