Plan B: Using sentinel birds to track poultry viruses when you can’t obtain SPF birds
Sometimes the best way to identify disease problems is to use sentinel birds along with other diagnostic tools, but the specific-pathogen-free (SPF) birds used for this purpose aren’t always readily available.
In these cases, broilers can be used instead if they’re hatched by the broiler company and are raised in isolation.
SPF birds are not only raised in isolation, they are also guaranteed to be pathogen-free, so any viruses or diseases isolated from them come from the field, Tim Cummings, DVM, senior technical services veterinarian, Zoetis, told Poultry Health Today.
Cummings cited a case with a company experiencing respiratory problems in its flocks. Diagnostics were being performed and they also wanted to include sentinel birds, but SPF birds weren’t available at that time.
Instead, they used the broiler company’s own day-old chicks that were hatched and placed in isolation to minimize exposure to any disease.
At 4 weeks of age, 10 each of the isolation-raised chickens were put in pens in 20 chicken houses, each on a different farm. Those birds were used as the sentinel birds. A week after placement on farms, the birds were collected. Samples were taken from tracheas, lungs, kidneys and cecal tonsils and were submitted for virus isolation.
Cummings said the viruses isolated on all 20 farms were vaccine viruses, which indicated there weren’t any variant bronchitis viruses in the field causing problems. Since this effort was a follow-up to vaccination changes made by the broiler company, the sentinel birds confirmed that no new bronchitis vaccines were needed.
The veterinarian cautioned that while producers can use their own broilers versus SPF birds when trying to isolate diseases from broilers, there’s no guarantee they’re pathogen-free even when raised in isolation.
He also noted that, “when we put these broilers in the chicken houses, they’d never been exposed to coccidia, so some of them had rip-roaring cases of coccidiosis when we sampled them.”