Use of multiple strains of infectious bronchitis vaccines to induce protection against new IB variants

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USPOULTRY (www.uspoultry.org.) and the USPOULTRY Foundation announced the completion of a funded research project at the University of Delaware in Newark, Del., in which researchers found that European infectious bronchitis vaccine does not protect against U.S. strains.
The research is part of the Association’s comprehensive research program encompassing all phases of poultry and egg production and processing. A brief summary of the completed project is shown below.

Project #F065: protection provided by multivalent Infectious Bronchitis Virus vaccines against challenge with current U.S. strains and variants

Dr. Jack Gelb, Jr., University of Delaware, Newark, Delaware, USA

Dr. Jack Gelb and colleagues recently completed a research project in which they examined the use of multiple strains of infectious bronchitis vaccines to induce protection against new infectious bronchitis variants. They found that combinations of existing vaccines did not provide protection to the new strains. Inclusion of the European 4/91 vaccine also failed to provide significant protection against current variant strains of infectious bronchitis.

Outbreaks of infectious bronchitis (IB) may be the consequence of improper vaccine application and associated vaccine back-passage or may be due to novel, non-vaccine related strains, often referred to as variants. Modified live vaccines are commercially available to help control the disease, which is caused by the numerous strains of infectious bronchitis virus (IBV). The most effective strategy has been to vaccinate chickens with commercial vaccines containing IBV strains that are most like those found in production settings. A limited number of vaccine strains are available to control IB. Many are strains that have been used for years; Massachusetts (Mass), Connecticut (Conn), Arkansas (Ark), and Delaware (DE) 072/Georgia (GA) 98. In 2014, a newer variant, GA 08, received a USDA conditional vaccine license.
In recent years, chicken health professionals have had interest to evaluate the European/International 4/91 vaccine because of its reported ability to induce a broad spectrum of IBV immunity. A vaccine capable of inducing protection against many different types of IBV is of practical and economic importance. U.S. trials that included the 4/91 strain have been few since these vaccines are not licensed for use in U.S. poultry. The objective of this research was to determine how best to utilize current vaccines as well as to evaluate the ability of the international 4/91 vaccine to protect against U.S. IB viruses.

IBV vaccines are often applied multiple times and in combination. Prior research has demonstrated that the Mass/Ark vaccine combination has been shown to offer some cross protection against unmatched serotype viruses found in the field. Since live IBV vaccines are known to interfere with live Newcastle disease virus vaccine replication and resultant immunity, it is likely that interference can also occur between IBV vaccine strains. Massachusetts IBV vaccine virus replication was not impacted by concurrent delivery with other IBV vaccines; however, replication of Arkansas and Delaware type viruses were. Observed differences did not consistently impact protection from virulent challenge 21 days after vaccination. In terms of vaccine efficacy, Massachusetts and Arkansas challenge data showed the greatest variation between the different vaccine programs. All vaccination programs, regardless of match to challenge virus, did decrease oral IBV shedding compared to non-vaccinated birds. Lowering the amount IBV in the production environment may help limit transmission.

The ability of commercial IBV vaccines to induce protection against current relevant and evolving variants needed to be reassessed due to changing vaccination practices (available vaccines, application methods, etc.). However, the selection of vaccines permitted for use should be limited to viruses present in a region. Introduction of IBV vaccines containing strains not found in a region may further complicate the management of IBV as well as overall poultry health for years to come. Our study found that the addition of the 4/91 vaccine to a multivalent IBV vaccine program did not significantly improve protection against currently circulating variant viruses GA08, DMV/1639/11 and PA/1220/98.
The best approach to protecting flocks from variant IB viruses continues to be:

1. Select vaccines that are genetically related to the IBV challenge viruses in a region;
2. Select a vaccine with a good titer; and
3. Ensure the proper handling and administration of the vaccines, which includes the consistent delivery of at least a full dose/chick.