Almost every flock will experience an outbreak of disease or parasitism at some time, but good management and biosecurity measures can go a long way to protecting your flock and minimizing problems. The first thing every bird owner should do is find a veterinarian familiar with poultry and work with that person to establish a strong flock health program. Your veterinarian will know which vaccinations may be needed in the area where you live and can assist you with a vaccination program appropriate for your flock. Many small flock owners never vaccinate because they think their birds will not be affected. However, anyone attending shows, working with 4-H members and their birds, or bringing in outside birds should vaccinate. Many diseases are very easily transferred by other humans, and birds that appear to be the picture of health can be carriers that constantly shed viruses. Some diseases, such as Marek‘s disease, can never be thoroughly gotten rid of – once your premises are contaminated, they are considered to be contaminated forever.
Always get a veterinarian‘s recommendation first, as vaccinating for one disease may cause another to become worse. Symptoms of some diseases may be confused with other conditions, so a serology test is needed for confirmation. Some diseases affect all poultry, others only some. Again, work with a veterinarian to establish a solid flock health program.
Source: Purina Poultry