Bio-security is a set of management practices that can reduce the possibility of introducing or spreading disease-causing organisms onto and between sites.
Most disease-causing agents enter the chicken from the beak and nose while eating, drinking or cleaning its feathers, or during breathing.
Some diseases infect through the wounds and some can infect by contact with droppings, litters, and other contaminated stuff.
Some infectious diseases can also be transmitted from the hen to its offspring through the eggs.
When infectious organisms enter the chickens, the symptoms of infection do not appear rapidly, rather, multiplying in the body and the symptoms can be seen later.
