A strategic shift toward rotational vaccination programs could help poultry producers reset disease control effectiveness, particularly for infectious bursal disease (IBD) and Newcastle disease, as field viruses adapt to overused single-approach strategies.
Rotating between vectored and live vaccine programs prevents field virus populations from developing resistance patterns, said Dr. Eric Shepherd, poultry veterinarian with Zoetis.
"What we have seen over time is that as companies have over relied on their vectored products, you will start to see the variant populations of bursal disease in the field start to learn how to evade these vaccines," he added.
A rotational approach switches between live vaccines that contain a modified, weakened live virus and a vectored vaccine that takes advantage of a “Trojan Horse” method that inserts pieces of a pathogen into a harmless vector virus. It works by forcing highly contagious viruses like IBD to adapt to different vaccine challenges, essentially putting pathogens "on their back foot," Shepherd noted.
When producers switch from vectored IBD programs to immune complex vaccines, the coated antibody technology will delay vaccine activation until birds can properly handle it, typically around two to two and three weeks of age, while crowding out and blocking variant IBD strains.
The reset approach can help improve flock performance. Research shows that birds with stronger immune function show better late-flock survival, reducing losses from secondary infections including gangrenous dermatitis, E. coli and inclusion body hepatitis.
Strategic implementation requires surveillance
Successful rotation programs depend on robust field monitoring to determine optimal switching points, including routine bursal sampling during posting sessions, with in-house PCR processing to track field challenge patterns and timing.
Most producers implement rotational changes during spring months (March-April), maintaining alternative programs through fall (September-October). Visual assessment using bursal boards allows veterinarians to photographically document changes in the lymphoid organ in poultry over time, providing clear evidence of program effectiveness.
"The beauty of these bursal boards is you can lay them down one by one on a table and look at them through photos over time to see how this has changed while on different vaccine programs," Shepherd noted. “A picture is worth a thousand words.”
