For many diseases due to microbes or the like, proliferation of microbes themselves is a cause of a symptom. However, there were cases where a substance released by the microbes is a cause of a symptom. In such cases, when attempting to treat a disease with an antibody, it was necessary to obtain an antibody against an antigen that is a substance causing the disease. However, it was difficult to find the underlying substance causing the disease among substances released by the microbes. An antibody (polyclonal) binding to not only an antigen but also to a substance, which is secreted by the antigen and accelerates the deterioration of a symptom, is obtained by immunizing birds with a lysis solution produced from lysing microbial cells as an antigen. Further, an antibody obtained with a surface protein of a virus as an antigen is expected to inhibit an infection by a virus.
