Emerging Technologies in Production and Mode of Delivery of Poultry vaccines

Dr Udi Ashash Abic Biological Laboratories Teva Ltd, Israel 

Vaccination of poultry, along with other means, is defiantly the most efficient way of preventing and controlling infectious diseases. Disease prevention is not the only animal health usage of vaccines as recently vaccination has also been used for other purposes like production and welfare.  Legislation and general perception against some "old fashion"  veterinary prophylactic measures, such as AGP's or mass slaughtering of livestock to control hazardous diseases, serve to further promote the use of vaccination as an alternative disease control strategy. Recent progress in veterinary research e.g. progress in animal genetics and better knowledge in veterinary immunology, have helped to develop more effective and safer vaccines. This development does not come easy, as there are several obstacles to the development of new vaccine types: Economic barriers (costly investments), Scientific obstacles (antigenic variability of some pathogens IB AI and lack of knowledge) and the last but not least: public perception (coming from ignorance..)  Regarding the consumption of food products derived from animals vaccinated with vaccines based on genetic manipulations.  The technologies arising from both animal and microbial genetic research is enabling the producers and users to gain a better understanding of: the pathogen's biology: the host immune system, and host–pathogen interactions. These new tools are applied in the discovery of highly effective vaccines for poultry.

 Vaccines and the ever changing viruses and bacteria

Antigenic diversity among some viruses is well known and occurs as a result of rapid mutations during replication and genetic interactions in co-infections of related viral disease strains. Variants which have acquired advantages (e.g. ability to spread or to avoid host immunity) become a major disease hazard to poultry and humans. Examples of antigenically diverse poultry viruses include Avian influenza, Corona viruses (IB) and others. In order to get a match between the vaccine and the field strains (effective vaccination) surveillance programs to monitor circulating serotypes and their evolution is required.

Viruses are basically simple in structure and it is possible (now days) to develop Recombinant and Subunit vaccines that have cross-protection within and between serotypes and to enable a safer and more effective vaccination.

An example to that can be the development of a Subunit vaccine for IBD based on the VP2.

Vaccines based on killed pathogens or sub-unit antigens are safer but require adjuvant to achieve efficient immune reaction. Unfortunately, most conventional adjuvant are poorly defined, complex substances that fail to meet the desired criteria for safety and efficacy. A new generation of adjuvant must be developed for safer, more potent inactivated Sub-Unit vaccines.

Bacterial diseases cause losses due to the disease itself, treatments costs and the ever emerging of drug resistant strains that is influencing both humans and animals. On the other hand, bacteria are antigenically diverse so bacterial pathogens pose a big problem to the industry and it is difficult to develop bacterial vaccines for the control of bacterial diseases (e.g. clostridial diseases, NE, mycoplasma etc.) Possible solutions include: Identifying the important antigen or antigens and then sequencing bacterial genomes to obtain the protein(s) that are capable of inducing protective antibodies. The most sophisticated approach would be to reveal the common (preserved) surface-expressed proteins present in all the isolates. So far this approach has been successful in controlling bacteria in humans and the way is now open for its application in veterinary medicine.

Poultry vaccines are widely applied to prevent and control viral and bacterial diseases. Their use in poultry is crucial due to the high growth rate, very short life cycle and quick spreading of the diseases in highly dense poultry population.. Vaccines and vaccination programs vary broadly in regard to several local factors (production type, local disease, costs vs. hazard balance) and are generally individually managed by the producers. However, the main issue is protection and there is a need for highly efficient viral and bacterial vaccines that will allow protection at minimum cost ( e.g one vaccination enough for life) + minimum to no handling.

Additionally, the industry should also look for "easy to present" or "user friendly" vaccines and vaccine application a nice example to that will be live vaccines in tablet form.

Vaccines: Answer to drug resistance in parasitic disease?

Antiparasitic drugs have been used successfully to control parasitic diseases in animals for many years, as they were considered safe, cheap and effective against a broad spectrum of parasites. However, some parasites (e.g coccidia) have developed drug resistance and the issues of residues in the food chain and in the environment have made the use of some drugs ineffective and unsafe for human consumption ( e.g. some Anticoccidials). Control methods of parasitic diseases with vaccines may provide attractive alternatives. Live attenuated parasite vaccines are already found in the market and sub-unit vaccines are beginning to emerge.

An example would be the poultry coccidiosis vaccine - CoxAbic

For sure, it is necessary to research the parasite genes and the role of parasitic proteins in the pathology.  This can lead to the identification of crucial antigens, which could then be produced and used to create protective immune response.

The use of vaccines for the control of Poultry diseases

First it should be emphasized that vaccines can not realistically be expected to provide 100% protection under field conditions. Nowadays, the poultry industry in many countries is involved in import and export of products and genetic stocks and organized in large scale integrations so vaccination must not be regarded as an ultimate alternative to other disease prevention management techniques like strict bio-security or what ever is needed for contagious diseases control.

The vaccination strategy should tailor-made and adjusted to the local factors: Type of poultry and type of farm organization (industrial or rural), stock density, area disease epidemiology (prevailing disease situation), availability of vaccines, resources (quality and availability of manpower, equipment) vaccine monitoring abilities, Costs. The goal of the program is that chickens will develop immunity to diseases found in the area. This immunity must provide the following:

1.     Reduction of the susceptibility to infection ( Increased infection dose is needed to trigger disease)

2.     Reduction of shedding

3.     Protection against the clinical form. (At individual level)

Conclusion remarks

Recent molecular research has opened the way to better understanding of the pathogen-host interactions. This has given the poultry industry the chance to benefit from a user friendly and more efficient vaccines for disease control.

The research breakthrough must be combined with industrial development of commercially low-cost vaccines for mass use.

Ref.

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