Live virus vaccine is effective against disease that impairs bird immunity – The Rural Gift

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by Eva Hunka *

Our country produced more than 6 billion broilers just last year, according to a report by the Brazilian Association of Animal Protein (ABPA). In addition, according to the survey, Brazil produced more than 49 billion eggs for consumption in the period – something that amounts to more than 5.5 million eggs per hour. It is evident that this sector has grown constantly, helping in the production of food and in the movement of the national economy. Therefore, it is necessary to pay special attention to the health and well-being of these animals.

One of the major problems of Brazilian poultry is Gumboro Disease, which has a high prevalence in the country, being responsible for high losses in national and worldwide farms. The disease was first described in the 1960s and still today motivates research on how to protect birds from the virus that causes the disease, with the aim of stimulating active immunity and minimizing the effects of maternal antibodies – which inactivate conventional live vaccines .

Even after so many years, researchers continue to invest technical and economic resources to prevent and control the disease. This is because the virus affects an important primary lymphoid organ of birds, the Fabricius pouch, and the infection of this organ compromises the immune response mediated by B lymphocytes (which constitute the immune system) and also the production of antibodies. After being infected by the virus (IBDV), birds tend to develop temporary or permanent immunosuppression, due to the dysfunction of the immune response, becoming susceptible to diseases.

The reduction in immunological capacity can be slight, without any associated problems of greater susceptibility to diseases, but these birds can also respond poorly to vaccinations against other infectious agents and are more susceptible to other diseases, especially those with high morbidity, common to some respiratory viruses, such as infectious bronchitis, for example, which is usually accompanied by secondary infections such as Escherichia coli (E. coli). This is reflected in the zootechnical results that result in economic losses.

As a classic immunosuppressive viral disease, Gumboro Disease can serve to illustrate the complex mechanisms involved in the disease in young birds. In day-old chicks, Fabricius’ Bursa (BF) is of great importance as a source of B lymphocytes. These lymphocytes are necessary to produce immunoglobulins. If the Bursa is compromised, immature B lymphocytes are attacked by the virus, resulting in its destruction and leaving the bird more susceptible to viral and bacterial pathogens. If B cells are depleted, the bird will not be able to adequately generate an antibody response to a new pathogen, including vaccine strains, in which case the situation will deteriorate to an immunodeficiency-like state.

In a few days after infection by a very virulent strain, a young bird’s entire immune system can collapse. In such cases, these birds can become ill due to opportunistic and saprophytic bacteria, which are usually harmless to healthy chickens. In susceptible birds, the virus will cause high direct mortality and suppress the bird’s ability to develop good immunity after vaccination, making them more susceptible to secondary infections and higher mortality. Thus, passive immunity plays a major role in protecting early infections from IBDV in the early days of the bird.

For this reason, care for the mother’s vaccination program will ensure a good level of maternal antibodies at birth. At this point, it is good to remember that these precautions go beyond the choice of the vaccine, and are closely related to the quality of the application, since vaccination in these birds is totally dependent on the human factor and susceptible to important errors such as underdosing, errors in the application site and even vaccination made from empty vials, resulting in low immunity and unevenness in the antibody titers that will be transferred to the progeny. In this sense, with the concepts of Aviculture 4.0, the new vaccination equipment allows greater control of the entire vaccine injectable process in the farm, in real time, or even in the making of more strategic decisions based on personalized data collection.

When we talk about fighting Gumboro Disease, the best way is prevention through vaccination combined with a robust biosafety program. Companies have a clear objective of making vaccination programs simpler and simpler, but they have the challenge of keeping them efficient and safe, even when they happen only in the hatchery, with a single dose. In the case of protection against IBDV, we need to remember that it is not just a question of avoiding the clinical form of the disease, but we also need to be aware of the immunosuppression that can come in the subclinical form, or even some vaccine strains. The choice of the appropriate strain for each challenge, which is strong enough to fight the very virulent and safe to the point of not affecting the bird’s immune system, is essential for the success of the vaccination program.

Programs with live vaccines, in addition to providing a more complete immune response, as it is an integral virus and with different proteins capable of stimulating the immune system, still have an important role in colonization and vaccination of the environment, which significantly reduces viral load of the field strain. Phibro Saúde Animal recently brought to Brazil the MB-1, the first live vaccine in the segment in the country, capable of forming a natural immunocomplex with maternal antibodies and that can be used safely in broilers, broilers and laying hens, with a single dose in the hatchery.

The natural immunocomplex, formed with MB-1, adapts naturally to the level of maternal antibodies, and therefore, the balance between antigen and antibody is perfect, as there is no “artificial” antibody causing an “imbalance” in the relationship between them. In addition, the strain has a high invasiveness and dissemination capacity and its use promotes renewal in the viral population of the environment, helping to control the high field challenge. This differentiated mechanism, in addition to the early serological response, also allows for the faster arrival of the vaccine virus in the Fabricius pouch.

Studies show that at 28 days of age, the natural immunocomplex vaccine (free virus) was identified in 100% of the samples, followed by positive identifications in an equal percentage (100%) up to 40 days of age. The “artificial” immunocomplex vaccine strain was identified at 28 days of age in only 33% of the samples, and from 32 days on in 100% of them, however on the 40th day, this number dropped to 83.33%. All of this contributes to the genetic potential of birds to be exploited. And the protection of animals, in turn, ends up being reflected in positive zootechnical results, which are good parameters for assessing whether the vaccination program is adequate for each reality, guaranteeing the sustainability and profitability of Brazilian poultry, as well as health and health. animal welfare.

* Veterinary doctor, master in preventive medicine and biological business manager at Phibro Saúde Animal

Source: Assessoria

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