Immunity and Disease
« Thread started on: Apr 4th, 2007, 05:30am »
http://edis.ifas.ufl.edu/VM011 (excerpt) "Nonspecific Immune Mechanisms Nonspecific immune mechanisms include the innate or inherent ways in which the chicken resists disease. This protective system is often not considered when designing a poultry health program. Many programs tend to rely primarily on vaccinations and/or antibiotics to maintain flock health. The importance of nonspecific immune mechanisms should be realized. Examples have been included. Examples :
Genetic factors - birds may not have complementary receptors to allow many disease organisms to infect them. For example, some strains of chickens are genetically resistant to the lymphoid leukosis virus.
Anatomic features - many disease organisms cannot penetrate intact body coverings (skin and mucous membranes) or are trapped in the mucus secretions. Some nutritional deficiencies (biotin deficiency) or infectious diseases compromise the integrity of the body coverings, allowing penetration of disease organisms.
Normal microflora - the skin and gut normally maintain a dense, stable microbial population. This stable microflora prevents invading disease organisms from gaining a foothold. Improper use of antibiotics or poor sanitation can disrupt the balance of the microflora.
Respiratory tract cilia - parts of the respiratory system are lined with cilia, which remove disease organisms and debris. If the air in the poultry house is of poor quality due to high levels of dust or ammonia, the ciliary system may be overwhelmed and become ineffective.
Other factors involved in innate resistance include nutrition, environment (avoid heat/cold stress), age (young/old animals are more susceptible to disease), inflammatory processes, metabolic factors, complement and interferon. The reason that good management practices are important in maintaining poultry health is better understood when the nonspecific immune mechanisms are defined. For example, poor sanitation or the overuse of antibiotics may lead to a disruption of the normal microflora; poor nutrition may lead to deficiencies that allow disease organisms to penetrate the protective body coverings; selection of disease resistant strains of chickens may preclude or lessen the effects of certain diseases. "