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-->Introduction

-->Main problems associated with vaccination at the hatchery

-->The development of new equipments

-->The breakthrough of new vaccines

-->Main advantages associated with vaccination in the hatchery

-->Conclusion

 

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VACCINATION IN THE HATCHERY- THE ASSURANCE OF A GOOD START -

By Dr. Yannick GARDIN, DVM, Scientific Director – Ceva Santé Animale – Libourne, France

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INTRODUCTION

One of the key challenges of the poultry meat industry for today and tomorrow is the control of broiler health. This is not only to avoid disease outbreaks, but more importantly, to protect the full expression of the genetic potential. Protection weighs heavily on the economy of the production and limits contamination by zoonotic pathogens, which could significantly decrease the commercial value of the final product.

The backbone of any sound policy aiming at controlling broilers health and reducing the risk of disease is biosecurity, and no real and long lasting success can be expected in this area without real and solid implementation of it at both breeders and broilers levels including the hatchery.

Vaccination is a complementary approach to biosecurity and there is no place today where we can actually think of dropping it. However, major changes are occurring in this field aiming at making vaccinations easier to apply, less expensive and more efficacious. This is why vaccination at the hatchery has recently gained such popularity and is developing quite fast among the poultry industry.

The objective of this article is to draw the main lines that explain this success.

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MAIN PROBLEMS ASSOCIATED WITH VACCINATION AT THE HATCHERY

For many years, considering quality, reliability and cost effectiveness, vaccination at the hatchery had been regarded as the optimum situation for vaccine application by poultry production people. However, until recently, only a few vaccines could honestly be recommended to be given at the hatchery with consistent (Marek’s disease MD, Infectious Bronchitis IB, Coccidiosis) or acceptable (Newcastle Disease ND, Swollen Head Syndrome SHS) efficacy.

The main reasons why vaccination against other diseases like Infectious Bursal (IBD - Gumboro) Disease, Laryngotracheitis (ILT) or Newcastle disease was not possible were:

• The lack of adapted or reliable equipments;

• The problem of interference between Maternally Derived Antibodies (MDA) and live attenuated vaccines;

• The residual pathogenicity of some vaccine virus.

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THE DEVELOPMENT OF NEW EQUIPMENTS

One of the main requests for vaccination to be given at the hatchery is the possibility to make it automatic and fast, with a low percentage of not or badly vaccinated chicks and a reduction in costs associated with vaccine application. Many developments have recently been made in this area and today, powerful and users friendly equipments are available to poultry producers for vaccination by eye-drop, coarse spray and fine spray, subcutaneous injection at day old and “in-ovo” injection at 18 – 19 days of embryonic life. Some of these equipments also allow association of two or more vaccinations (spray and injection, double injection) at the same time.

However, although reliability has improved and sophistication added, they should not be regarded as perfect and an eye should always be kept on them as well as on the operator, and the quality of vaccine application regularly checked. Various devices and procedures have been developed for this purpose.

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THE BREAKTHROUGH OF NEW VACCINES

Many new vaccines have recently been introduced in the market, and more are still to come. Because of them, the range of vaccines applicable at hatch has enlarged and the cost benefit ratio of expensive equipments like “in-ovo” injectors strongly modified in favour of hatchery vaccination.

Among these new products, the following are worth to mention:

• Live attenuated Newcastle Disease vaccines of the “enterotropic” type: these viruses are naturally apathogenic for the chickens and can induce local immunity without creating lesions of the trachea as classical “tracheotropic” live ND vaccines do, leaving chickens more susceptible to secondary viral or bacterial infections. With this new category of vaccines, no rolling infection is observed, growth is improved and consumption of antibiotics is reduced. This category of apathogenic live attenuated ND vaccines has really contributed to the spreading of ND vaccination at the hatchery.

Image 1 Cevac^® Vitabron L - Live freeze-dried vaccine: PHY.LMV.42 and Massachusetts H20 strains

• Immune complex IBD (Gumboro) vaccines: based on a combination of vaccine virus and specific homologous antibodies in very well defined proportions, these vaccines have the capacity to delay the release, and hence the replication, of the vaccine virus up to an age where Maternally Derived Antibody level has reached a level that is no longer capable to neutralize it. Because of their reliability and their strong efficacy, in particular in areas where the very virulent form of the disease is present, this new type of IBD vaccine is becoming more and more frequently used all over the world.

Image 2 Structure of combination of IBD virus and specific homologous antibodies

• Recombinant (IBD, ND, ILT, AI, etc.) vaccines: these vaccines are made from a gene extracted from a virus against which protection is looked for. This gene, encoding for a protective antigen, is introduced in the genome of another virus used as a carrier (the vector). Indeed, this vector must be apathogenic for chickens like Fowl Pox (FP) virus for example, and preferably not susceptible to homologous MDA, which is the case of the Herpes Virus of Turkey (HVT) also used to protect chickens against the mild forms of the Marek’s disease. The way these vaccines induce protection is something really new and a lot of research work still need to be done until we actually fully understand it. Their capacity to breakthrough MDA is real when HVT is the vector. Besides, since HVT persist forever in the vaccinated animal, long lasting protection is observed. This is very interesting when considering protection against ND.

Image 3 Structure of recombinant virus with a extracted gene in a vector

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MAIN ADVANTAGES ASSOCIATED WITH VACCINATION IN THE HATCHERY

The main advantages associated with vaccination in the hatchery are the following:

• The vaccine is handled by a few people that can be well trained and monitored: globally speaking, it is much easier to control 5 workers in an hatchery than 200 farmers spread on a wide territory. It is also easier to make sure that the cold chain recommended for storage of the vaccines from the producer to the end user is respected.

• The chickens are kept in boxes, which make it much easier to manipulate than when they are spread all over a poultry house.

• Sophisticated, and consequently expensive equipments are more affordable for a big structure like a hatchery than a for a poultry farm. Also equipments are better monitored and better maintained at hatch than at farm.

• Spray vaccination, which is the best method for administration of respiratory vaccines like ND or IB, is much easier to apply and consequently more efficacious when given in the hatchery than when applied at farm.

• Injection required for vaccines based on new technologies like immune complex or recombinant, can only be applied with reasonable cost and quality at the hatchery.

• And of course, hatchery is the only place where “in-ovo” vaccination can be applied.

Recent field trials conducted around IBD vaccination have included very close comparison of efficacy between vaccination at the hatchery and vaccination at farm. Results were just unbelievable. In some organisations, percentage of not protected flocks, despite heavy vaccination programme, was as high as 20 to 30%, and sometimes even higher!

In hatchery vaccinated flocks, percentage of protected flocks almost always reached 100%.

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CONCLUSION

For many reasons including reduction of the duration of the growing period for broilers, increasing cost of the work at farm, as well as the recent availability of adapted equipments and new types of vaccines, vaccination at the hatchery is becoming more and more common in the poultry world. It globally helps the producers at reducing costs and improving efficacy of vaccine prevention. It is also a field of very active research for vaccines producers and there is no doubt that this is where the future of broiler vaccination stands. Vaccination at the hatchery is a real improvement for vaccine prevention, and this is really a promising way to better control diseases.

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