Using the wrong antibiotic may actually make the disease problem worse. Indiscriminate use of antibiotics can affect the good bacteria that help keep everything in balance. When these have been destroyed, pathogens are more likely to invade. Also, pathogens are more likely to become resistant when antibiotics are over used. Antibiotics will not have any effect on viruses.
Vaccination is one method of preventing infectious diseases.
There are vaccines for both viral and bacterial diseases. Most of the vaccines used in commercial poultry are modified live vaccines. In order for these products to protect the bird, they must create a mild form of the disease. The body must respond to this disease in order to develop immunity. If a bird is in poor health, disease will be easily produced.