Viral genotyping can improve infectious bronchitis control

Infectious bronchitis virus continues to cause losses for broiler and layer operations around the globe in spite of extensive vaccination and diagnostic efforts. Dr. Richard Currie, veterinarian, molecular biologist, and co-founder of x-OvO, said that there are three types of diagnostic test for determining the infectious bronchitis status of a flock of chickens. He told the audiences of the WATTAgnet.com webinar, Infectious Bronchitis – Using PCR analysis to identify the predominant strain, sponsored by MSD Animal Health, that three diagnostic methods, ELISA, Hemagglutination inhibition, and molecular diagnostics (PCR), all have distinct advantages and disadvantages.
Currie explained that ELISA testing can be low cost, automated and convenient, but it doesn’t differentiate between different subtypes of the virus. Hemagglutination is low cost, serotype differentiation is possible and he said it can be more useful than ELISA for the construction of an appropriate vaccination program. Unfortunately, he said that the results of Hemagglutination inhibition are sometimes not clear, because there is no differentiation between vaccine response of the same serotype.
Genotyping the virus lets you differentiate vaccine strains from true field viruses so you know where your disease challenge is coming from, said Currie. He explained that vaccines from the same serotype of bronchitis virus can still be different genetically. So vaccines from different companies will be different genetically even though they are the same serotype. Currie said that using DNA sequencing is what lets you differentiate between different vaccine strains and field viruses
Currie’s three practical applications of infectious bronchitis molecular diagnostics:


1. Ensure your flocks are vaccinated
In a test of 300 flocks of commercial broilers in the EU, Currie reported that 18 percent were negative for Infectious bronchitis virus (which means they weren’t effectively vaccinated), 8 percent were sample untypeable (Usually meaning they were exposed to a field type Bronchitis virus that you can’t identify because there is so little genetic material).


2. Vaccinate against true field viruses
This method allows for clear differentiation of vaccine strains from field viruses.
When applied to field outbreaks, it can clarify the apparent large number of field viruses and allow their reclassification.


3. Optimize protection: determine what vaccination programs are associated with the fewest field viruses
Currie explained that current technology does not provide conclusive proof via sequencing analysis that a particular vaccine will protect against a certain field virus. However, molecular characteristics can be identified that are supportive of a protectotype response of a particular vaccine strain for an identified field strain.
To learn more about the field data Currie has gathered on the genotypes of infectious bronchitis virus found in broilers in layers in Europe and the Middle East view the archived webinar.