Virus-induced immunosuppression in Russian poultry farming

Eduard Djavadov All-Russian Research Veterinary Institute of Poultry Science, Russia

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Virus-induced immunosuppression in poultry is a key factor in Russian poultry farming. In the context of large-scale poultry farming, typical of Russia, one of the main ways to confront communicable diseases is vaccination. Immunodeficiencies are common in infectious, especially viral pathologies. Immunodeficiency temporary, transient nature is accompanied by acute for many infections. Irreversible immunodeficiency occurs in acute lesions of the lymphoid organs, such as Mareks disease (MD) and Gumboro disease (IBD). Especially dangerous is the persistent and congenital viral infections in which the permanent functional deficits are accompanied by immunopathological unpredictable consequences.

Due to lack of specific immune systems, resulting in infectious diseases, as well as the application of some vaccines, is the damaging effect of pathogens directly or indirectly on a variety of stages and forms immunogenesis. Stem cell damage and disruption homing effect (settling B- and T – lymphocytes secondary and peripheral organs of the immune system, i.e. B- and T -dependent areas of lymph nodes) is accompanied by inhibition of antibody production, lymphokine. Damage lymphopoiesis – the central link of the immune system leads to the occurrence of structural and functional deficits of individual T- and B-dependent mechanisms and reactions. Violation myelopoietic causes inhibition of phagocytic, bactericidal function of polymorphonuclear leukocytes, and the whole complex of anti-infective antigen is presented cell functions of mononuclear phagocytes. Also in infectious diseases is possible to suppress the complement system and overall cooperation of immune system cells, as well as a violation of individual regulatory relations.

This phenomenon must be considered in vaccine preventable, as expressed by the immunosuppressive potential pathogen (eg viruses MD, IBD, chicken anemia virus (CAV) inhibited the formation of antibodies by vaccination against other diseases (Newcastle disease (ND), infectious bronchitis (IBV), and etc.).

The situation can become complicated when using the associated live vaccines because of the inclusion competition interactions, as well as using contaminated biological products, which leads to the immediate damage to the immune system. Great loss of certain subpopulations of immune cells leads to the loss of one of the links of immunity and thus lower resistance. The tendency to persistence is typical for these viruses. The persistence of these pathogens leads to a more severe course of the disease by increasing its duration and causes significant damage to the health of the birds.

In terms of the pathogenesis the following processes can occur in the immune system:

  • along with virus persistence infected cells can function properly, slow down or increase their activity (increased activity of suppressor cells);
  • upon infection changes ability of lymphocytes to normal migration that leads to quantitative changes of populations and subpopulations of lymphocytes in the lymphoid organs and blood vessels;
  • under some viral infections lymphoid specific zones decreases, which is accompanied by loss of function and results in immunodeficiency;
  • viruses are able to stimulate the expression of new cellular antigens (the main complex histocompatibility), which are normally absent. As a result, the immune system is overloaded and excessive stimulation of immunoregulatory mechanism enhances the activity of suppressor cells;
  • lymphocytes, macrophages, infected or virus-transformed cell capable of producing lymphocytes, macrophages, infected or virus-transformed cell capable of producing tumor suppressor factors;
  • interferon has antiviral and immunostimulating activity, but under certain conditions it may be an immunosuppressant;
  • some components in the structure of virions, which are toxic to lymphocytes, turn it to immunosuppressive and contribute to the induction of suppressor cells indirectly;
  • inactivated virus or purified components of the virion may suppress the immune system;
  • damage to non-lymphoid tissue by viruses, including attenuated vaccinal viruses, causes suppression of the immune response;
  • the impact of the virus on the adrenal cortex may lead to corticosteroids stress and subsequent immunosuppression.

Development of viral infections and immunosuppression expression are influenced by various factors: genotype, age, presence of infections or other diseases, environmental factors. The susceptibility to infection can be increased by stimulation of immunity. The appearance of immunosuppression in most viral infections usually follows an active, often high immune response. Each vaccine is accompanied by immunosuppression.

Particular attention should be prevention of Gumboro disease. During replication of the virus Gumboro disease is the destruction of B-lymphocytes (mostly immature stage of their active division), which is one of the parts of the immune system.

Pathogen IBD, possessing exceptional lymphotropic, affects not only the seminary, but also the spleen, thymus, lymphoid tissue of the intestine, Garderov’s gland and probably the lymphoid tissue of the head. Formation of post-vaccination immunity against IBD is similar to the formation of post-infectious immunity due to field virus penetrate into the body, and it is through the total destruction of cells sac, and it is through the total destruction of the bursa cells. After the application of vaccine IBD “hot” strains bursal atrophy occurs, one of the main organs of immunity. As a result, post-vaccination reactions may occur related to the clinical expression IBD, expressed immunodeficiency accompanied primarily a manifestation of secondary infections (koliseptitsemiya) as well as lower resistance to viral respiratory infections, poor immune response to the introduction of live vaccines against Newcastle disease and infectious bronchitis. Another representative of the pathogens causing the immunosuppressive state bird is a chicken anemia virus. The target cells for the virus CAV are precursors of T cells in the thymus and bone marrow hemocytoblasts. The infection is often complicated by CAV secondary infections of viral and bacterial origin, such as Staphylococcus aureus, Clostridium perfringens, E.coli et al., that are manifested malignant edema, gangrenous dermatitis, colibacillosis and pulmonary aspergillosis. CAV-induced immunosuppression not only opens the door for secondary infections, but significantly reduces the immune response to vaccination against Marek’s disease and ND. Along with the current chickens anemia breakthrough immunity MD, ND, coccidiosis are often occurs. Similar to IBD the symptoms (bursitis, bleeding in the muscles) are misleading veterinarians, resulting in a misinterpretation of the epizootic situation in the poultry, the creation of schemes vaccinations that do not ensure effective prevention of infectious diseases. Associated with IBD for CAV and / or MD process causes severe immunosuppressive state accompanying with a significant increase in mortality, susceptibility to secondary infections of poultry, a sharp decline in economic indicators and the threat of emerging infectious diseases, particularly Newcastle disease. The bird at the joint infection IBD and CAV viruses is a significant reduction in T- cell and macrophage populations in the thymus and spleen, compared with monoinfection caused by CAV.

Created live vaccines against CAV does not improve the situation of the disease in Russia, and vice versa, as a result of the massive use of live vaccines, there is an active spread of the virus at a poultry farm CAV Russian Federation. It is one of the reasons for the increase in cases koliseptitsemiya spectrum of infectious diseases.

Marek’s disease virus depending on the type of infection caused by itself effects on B-lymphocytes and T-cells, destroying and transforming them into replication process. As a result, there are such macroscopic lesions atrophy of the thymus and bursa of Fabricius, degenerative diseases of the bone marrow and various internal organs, demyelination of nerve fibers, as well as the formation of lymphoid tumors affecting vital organs. Depressive state bird is typical clinical symptom MD throughout the infectious process. Vaccine against Mareks disease is effective only in the absence of secondary immunodeficiencies. Vaccines against BM immunocompromised due to infectious bursal disease and infectious anemia chickens do not provide full protection. It should also be noted that there is a strengthening the negative impact of pathogens and CAV, IBD on the body of the bird caused by a virus infection of chickens MD (including immunization with live vaccines against IBD), causing an increase in mortality and susceptibility to secondary infections, loss of productivity.

Reoviruses are widespread among domestic and wild birds and are the cause of many diseases of birds. Reovirus infection appears as reovirus tenosynovitis, malabsorption syndrome (syndrome of poor absorption, helicopter diseaseproventrikulit monocytosis, bonding cloaca) and others. Reovirus may cause abnormalities of the respiratory system, kidneys, heart and other organs of birds. The variety of pathologies linked to the ability of reoviruses persists in the immune body. Reovirus infection is most expressed in conditions of stress factors of different origin, associated with the flow with other infectious diseases, with immunodeficiencies. When IBD-induced immunosuppression in the reovirus infection is observed serious intestinal damage, inhibition of the synthesis of antibodies to reovirus, a long period of isolation from the reovirus lymphoid tissue and cells of the gastrointestinal tract. So the association with the CAV virus can manifest severe dermatitis in the wings (“Blue Wing”) and other parts of the body. Bird susceptibility to pathogens other infectious diseases, in particular anemia chickens, Newcastle disease, colibacillosis increases with disorders of the immune system caused by reovirus. Currently in poultry industry infectious disease in the majority of cases occur in the latent and subclinical form. This has a negative effect on the results of the immunological monitoring and preventive vaccinations for related infections, exacerbates a variety of concomitant pathological processes.

From The Potential For Poultry Production in Developing Countries.