IMMUNITY

1
IMMUNITY

• INTRODUCTION
• Definition
• Resistance of an organism to infection, disease,
  or other unwanted biological invasion.
• The immune system consists of group of cells,
  molecules and organs that act together to defend
  the body against foreign invaders that may cause
  disease, such as bacteria viruses and fungi.
• There are 2 types of immunity
• 1. Innate first line of defence skin, tears,
  mucus, saliva.
• 2. Adaptive second line of defence antibodies
• Immune system can be manipulated in farm animals
  to give protection against disease.
• Hyperfunction and hypofunction of immune system
  will affect farm animals. Both will retard
  growth.

2

• Hyperfunction
• Occurs as a result of over-functioning of the
  immune system. For example, this manifests itself
  as a number of allergic diseases.
• Hypofunction
• Occurs as a result Increased incidence of
  diseases and these diseases are more severe.
• Development and maintenance
• Depends on thymus, lymph nodes, bone marrow and
  spleen. It operates in 2 parts
• 1. Antibody product
• 2. Cell mediated immunity

3

• Types of antibodies
• Antibodies or immunoglobulins are of several
  types though they are made of similar units. The
  antibodies are large proteins molecules specific
  for particular antigens.
• Anti bodies have 4 main types
• 1. IgM Most important( during early primary
  response)
• 2. IgG Most important during secondary
  response.
• 3. IgA Protects serromucous surface.
• 4. IgE Protects against parasite, important in
  allergic reaction.

4

• Passive and active immunity
• Immunity can be active or passive.
• Passive is one that introduces antibodies
  produced by another individual into the body of
  animal concerned. For example during birth,
  mother gives antibodies to new-born via colostrum
  and milk. In cattle, sheep, goat, pigs and
  horses, transfer is entirely from colostrum for
  Day 1 and Day 2 after birth. Passive immunity
  generally decreases in level along with time.
• Active
• Immunity usually occurs through introduction of
  vaccines in body developing resistance to a
  certain disease. Usually this form of immunity
  lasts for a long time.

5

• Effects of disease on growth
• Disease in many cases can retard growth. Effects
  can be direct causing upset in metabolism and
  absorption which can lead to diarrhoea. An
  example of indirect response is animal consuming
  less feed.
• Some animal diseases can be transmitted to
  humans, and control of these types of diseases,
  known as Zoonoses, is vital to public health.
  Some diseases are Salmonellosis, Feline
  Leukemia, Ringworm and Coccidiosis.
• If the animal has been exposed to sufficient
  strong challenge, vector may not be able to
  express itself. Therefore the growth rate is not
  affected.
• If vaccination has been done, it allows optimum
  growth rate to manifest. Oral immunisation in
  pigs and cows with enteropathogenic bacteria has
  given these benefits.

6
conclusion

• The health of the body is dependent on the immune
  systems ability to recognise and then repel or
  destroy these invaders.
• It is important to know about animal immune
  system because when the animals suffer from
  diseases, it affects their productivity and the
  economic well-being of many industries.
• In general, the functioning of the immune system
  is still a mystery. With incoming technologies
  and researches, we are looking forward to have
  more information on the topic.