Protecting longer-life layers against infectious bronchitis
With many laying hens now remaining in production up to 500 days, it’s time to rethink infectious bronchitis (IB) protection protocols, says Dieter Vancraeynest, DVM, PhD, a poultry veterinarian at Zoetis.
Protection against IB starts in the rearing phase, with live vaccination with different serotypes, he said. The Massachusetts variant is generally considered the basis of any IB protection program, he added.
“This provides a good foundation for IB protection. Later, you have to top up with different serotypes, depending on the geographical area in which you are operating,” he stressed.
With wide variation in IB strains, the virus is a constantly moving target and there is no vaccine available to cover every serotype. Developing a successful IB vaccination program starts with diagnostics to discover which serotypes are circulating in a specific area, he advised.
While inactivated vaccines offer an effective boost for IB protection, the duration of immunity they provide is insufficient for today’s longer-life layers. Now, he said, producers need to top up protection against IB during the production cycle.
Label constraints limit the use of many IB vaccines during lay – not because the vaccines are unsafe or ineffective, he said, but because the manufacturers did not anticipate use at this stage when the vaccines were registered. However, he noted that recent tests on one commercial IB vaccine (Poulvac IB-QX) confirm that it can be used in lay without any safety concerns. This vaccine is effective against the QX strain, which is now among the most prevalent IB variants worldwide.
For emerging IB virus strains for which no homologous vaccines are available, vaccines that offer cross-protection should be used, Vancraeynest said. Such variants include Variant Q1 in Europe and Variant 2 in the Middle East.
Even when diagnostics are used, IB vaccination programs may not cover all strains in circulation, leaving birds vulnerable to collibacillosis and other bacterial infections triggered by the virus. Vaccination against Escherichia coli, good management, adequate ventilation and careful control of dust and ammonia levels therefore help to provide further protection.
Posted on September 8, 2017