FACTORS AFFECTING IMMUNOSUPRESSION AND THEIR CONTROL
JAI PARKASH ( PhD , LUVAS, HISAR )
Immunosuppression is a state of body when the immune system or humoral (antibodies) and/or cell mediated immunity is depressed. It is not a disease and has no clinical sign. Different factors from which it can be recognized are atrophy of lymphoid organs, increased mortality, less uniformity of flock, poor performance, less antibody titer against vaccination and increased chances of bacterial infection. Immunosuppression may be due to infectious agents, sudden change in managemental practices like feeding, watering, temperature, very high or low humidity, improper biosecurity, nutritional deficiencies, or combination of them.
Immune system of poultry can be divided into two categories :
- Non-specific – It fight against disease in many ways including body temperature, anatomic features, normal micro flora, respiratory tract cilia and genetic factors. Managemental practices play important role in poultry health like misuse of antibiotics or poor sanitation may lead to a disturbance of the normal micro flora; high concentration of toxins, poor nutrition may lead to deficiencies which allow the disease causing organisms to penetrate the protective body coverings, selection of disease resistant strains and many more.
- Specific immune mechanisms. It is acquired system consist of:-
Cellular includes cells that fights with antigens, except those associated with antibody production. The cells associated with this system are the T-lymphocytes. Some T-cells produce lymphokines (over 90 different ones have been identified) and some directly destroy disease organisms.
Non-cellular components consist of immunoglobulin (antibodies) and the cells which produce them. There are three classes of antibodies which are produced in the chicken after exposure to a disease or vaccination; these include Ig M, Ig G, and Ig A. All these are specific. Ig M is detected after 4-5 days , Ig G is the most important antibody which is appeared after 5 days and
Part of immune system in poultry are:
- Bursa of Fabricius.
- Thymus
- Spleen
- Bone marrow
- The lymphoid cell aggregates along the gut, the trachea, the oesophagus, the Harderian gland and the caecal tonsils.
- Circulating lymphocytes.
FACTORS AFFECTING AND THEIR CONTROL
Environment:
Immunosuppression in poultry is mainly caused by stress which can be by Managemental, Environmental, Nutritional or Any disease condition.
Short-term stressors leads to, available nutrients are used towards resistance against the bacteria, parasites and toxins etc.
Long-term (chronic) stressors make the birds more susceptible to infectious agents challenge.
Healthy Poultry needs optimum conditions of temperature, humidity, ventilation etc. Any variation in these causes the stress which increases the production of corticosterone ultimately leading to depletion of lymphoid organs like thymus, bursa of fabricius and spleen. High stocking density, low feeding and watering space etc. also affect the immune system in negative way by impeding the nutrient availability to the body. Also changes the intestinal microflora which causes poor digestion, watery faeces etc.
To prevent environmental stressors provide constant and uniform supply of good quality of fresh air to birds. Proper ventilation can only be achieved if the house has the proper number and capacity of fans, cooling pads and air inlets. Increase feeding and watering space and reduction in stocking density of birds help to control immunosuppression.
https://www.pashudhanpraharee.com/heat-stress-in-poultry-management-strategies/
Nutrition:
Well-nourished birds are immunologically more competent and have more resistance to diseases. Birds cannot develop their good immune system if they are nutritionally deficient. There are many vitamin, minerals and amino acids whose deficiency in poultry feed cause the immunosuppression like-
Vitamin E is stabilizing the cell membranes. Free radicals or oxidative compounds can be ingested through poorly stabilized fats, oils and animal byproducts. They are able to damage the cell membranes. Vitamin E is able to remove these oxidative molecules in this way it supports the immune system. Vitamin E deficiency causes the increase in no of free radicals which indirectly suppress the immune system.
Vitamin C deficiency lowers the speed of healing, increases the effect of stress so, suppress the immune system and also reduces the synthesis of corticosterone during stress conditions. Vitamin C is also important for the formation of white blood cells. Vitamin A deficiency leads to increase the chances of diseases like Newcastle disease, Infectious Bronchitis, Coccidiosis, Necrotic Enteritis, Mycoplasmosis etc. which suppress the immune system directly or indirectly.
Arginine acts as immune modulator and deficiency of methionine, valine, threonine, vitamin A, riboflavin, pantothenic acid, pyridoxine, sodium, chloride, zinc and selenium will have a negative impact on the immune system. Thus, these should not be deficient in feed to prevent immunosuppression.
To control the immunosuppression by nutrition it must be kept in mind that poultry feed is not deficient in any amino acid, energy, vitamin and minerals.
Infectious Diseases:
Almost all diseases of poultry can suppress the immune system; however certain diseases whose virus replicates in immune organs like bursa/ thymus, directly influence the immune system. These include Infectious Bursal Disease, Chicken Infectious Anaemia, Marek””s Disease, Reovirus infection, Newcastle disease and Avian influenza.
To control these infections, appropriate vaccination schedule for breeders should be adopted so that their chicks can have approciate maternal antibody levels against these diseases.
Mycotoxins:
Mycotoxins are the metabolites of fungi commonly called molds. They grow and produce toxins in grains and other poultry feed ingredients during growing or harvesting or storage of the crop. There are three types of fungi whose metabolites mainly affect the poultry feed ingredients. These include aspergillus, penicillium, and fusarium. Major ingredients on which these grow are maize, wheat, rice, and peanut meal.
Aspergillus produces aflatoxin, which impairs the immune cells functioning. Aflatoxin is also responsible for lymphoid depletion and necrosis in the bursa of fabricius, spleen and thymus and hepatotoxicity.
Penicillium produces ochratoxin A which is associated with a generalized impaired humoral and cell mediated immune responses. It is also nephrotoxic.
Fusarium produces Trichotecene and it suppresses the immune system in two ways, firstly, it is a strong tissue irritant and alters mucosal membranes integrity. Secondly, it inhibits protein synthesis and consequently interferes with antibody production. Measures to control the mycotoxins in poultry feed includes –
Ingredients for feed formulation should br free from mycotoxins
Proper storage of grains and careful feed manufacturing
Mould inhibitors like copper sulphate or organic acids or vinegar should be used in feed
Moisture level of feed and ingredients should be maintained below safe levels
Conclusions:
Immunosuppression causes poor production and economic losses, which necessitate its prevention for better flock health, vaccination response and performance and uniformity of flock. This can be achieved by controlling the infectious diseases, providing good management, maintaining appropriate environment and by good nutrition.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3047790/
