Immunosuppression in poultry causes and control

Published on: 8/9/2021

The immune system combats the antigens and ensures the good health status of the bird. It identifies almost all disease-causing agents, from viruses to parasitic worms, and differentiates them from the body´s cells and tissues

A chicken may become immune to a disease organism by producing antibodies itself or by obtaining antibodies from another animal. The organs or cells that are the part of the immune system in poultry are:

Bursa of Fabricius.

Thymus

Spleen

Bone marrow

The lymphoid cell aggregates along the gut, the trachea, the esophagus, the Harderian gland, and the caecal tonsils.

Circulating lymphocytes.

What is immunosuppression?

  is a state of the body when the immune system or humoral (antibodies) and/or cell-mediated immu­nity is depressed. is not a disease and has no clinical signs. 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 management practices like feeding, watering, temperature, very high or low humidity, improper biosecurity, nutritional deficiencies, or a combination of them. Each of the possible causes of immunosuppression must be considered to prevent the loss of production and economic performance.

Causes and Control

Environment:

in poultry is mainly caused by stress. Managemental practices. It is a fact that in stressed poultry, losses due to a disease increases. Under commercial conditions, the chicken is exposed to a variety of stressors that may adversely influence the immune system

Poultry demands optimum conditions of temperature, humidity, ventilation, etc. to produce efficiently. High stocking density, low feeding and watering space, etc. also affect the immune system in a negative way by impeding nutrient availability to the body.

To prevent environmental stressors provide a constant and uniform supply of good quality air to birds. Fresh air is required at all stages of production to

achieve potential performance from the birds. Proper ventilation can only be achieved if the house has the proper number and capacity of fans, cooling pads, and air inlets. With the help of proper ventilation harmful gases, temperature and humidity can be controlled. Increase feeding and watering space and reduction in stocking density of birds help to control immunosuppression.

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Nutrition:

It is well-known fact that well-nourished birds are immunologically more competent and have more resistance to diseases. A change in feed intake leads to a change in nutrient and energy intake. Birds cannot develop their good immune system if they are nutritionally deficient.  However, the commercial poultry feed is not deficient in nutrients and energy. It is well known that immunosuppression in poultry, causes a decrease in feed intake. There are many vitamins, minerals, and amino acids whose deficiency in poultry feed causes immunosuppression. e.g.

Vitamin E. Vitamin C deficiency lowers the speed of healing, increases the effect of stress so, vitamin A-deficient birds produced fewer Newcastle antibod­ies and a lower T-cell response. Deficiency in vitamin A increases the chances of diseases like Newcastle disease, Infectious Bronchitis, Coccidiosis, Necrotic Enteritis, Mycoplasmosis, etc. which suppress the immune system directly or indirectly. Without these supplemental vitamins, acceptable performance and carcass characteristics can not be achieved. Vitamins also augment disease resistance under conditions of stress. These vitamins exert their mechanism of action during stress by protecting immune tissue via a lessening of certain hormonal effects and oxidative damage, and improvement of cell differentiation and production.

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 mineral because these play a very important role in the functioning of the immune system.

Biosecurity

It encompasses the practices or measures adopted to minimize the invasion of pathogens on the poultry shed. Biosecurity, vac­cination programs, vaccines, and other important factors for the control of im­munosuppressive agents have been extensively researched. Poor hygienic conditions result in a pathogenic invasion from outside, which leads to a higher pathogenic load on birds; thus cause stress and immunosuppression. So, the incidence of immunosuppression can be thwarted by strictly employing biosecurity measures.

Prevent unauthorized entry to the poultry farm

Visitors and service providers to the farm must wear overalls and boots provided by the farmer.

Ensure the provision of foot washing baths at the entrance of each shed to disinfect the footwear prior to shed entry.

Vehicle movements onto the farm should be minimized, and vehicles or equipment that may have visited another farm must be washed before entry.

Where people or vehicles must move between farms on the same day without thorough disinfection between farm visits, movements should be scheduled from the youngest flocks to the oldest.

Adopt " All in the all-out system"

Establish regular sanitation and disinfection procedure.

Make sure all the workers practice sanitation strictly.

Take bacterial counts from the samples taken from different places at the farm and then apply proper disinfectant.

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, an appropriate vaccination schedule for breeders should be adopted so that their chicks can have appropriate 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. It is estimated that about 25% of the world''''s cereals are contaminated with known mycotoxins, while higher per­centages could be contaminated with tox­ins as many toxins are yet to be identified. No region in the world can eradicate these silent killers and their negative impacts on poultry production. 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.

. Followings measures should be adapted to control the mycotoxins in poultry feed.

Use of mycotoxins free ingredients for feed formulation

Proper storage of grains

Careful feed manufacturing

Mould inhibitors like copper sulfate or organic acids or vinegar should be used in feed

The 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 infectious diseases, providing good management, maintaining an appropriate environment, and by good nutrition. However, further work is required to investigate im­munosuppressive conditions and agents in poultry.