As the technology to identify strains of pathogens has improved, higher-resolution typing can help fight bacterial disease on-farm, according to Tim Johnson, Ph.D., professor of veterinary medicine at the University of Minnesota, who spoke September 12 during a university webinar.
Johnson said there are four methods commonly used for typing pathogens:
- Serotyping, which is very low-resolution phenotypic
- Virulence gene profiling, which is very low-resolution genotypic
- Fingerprinting, which is low- to mid-resolution genotypic
- DNA sequencing, which is high-resolution genotypic
The higher the resolution of the method, the more information that will be obtained from the typing, he said. With DNA sequencing, poultry farm operators can better select for vaccine strains or connect pathogens from one environment to another.
Why care about bacterial pathogens beyond disease?
Even without disease, Johnson said, pathogen load correlates with a bird’s performance. This is why it is important to identify the correct pathogens to target with a vaccine.
Because there are no vaccines on the market for Ornithobacterium rhinotracheale (ORT), a bacterium that causes respiratory disease in poultry, they must be created using strains found on the farm.
Ideally, operators would select a strain that is representative of the specific flock and make a vaccine against that strain, and then give it to the birds to protect against that pathogen. But, Johnson said, the big problem with prolonged use of a vaccine without switching is that, undoubtedly, the type of pathogen will shift.
“Creating a vaccine and expecting it to work forever is a bad idea,” he said. “You need genome sequencing/typing, you need surveillance to be able to understand how things change over time and when it’s time to switch to a new strain for a vaccine.”
Johnson outlined a six-step workflow for a successful vaccination plan:
- Complete extensive surveillance of on-farm strains
- Identify dominant problematic strains
- Create an effective autogenous vaccine that targets those strains
- Continue surveillance of those strains
- Predict the next vaccine combination
- Switch vaccine strains at least every 1-2 years
“It doesn’t work if not all these steps are followed and, furthermore, it doesn’t work if your method for typing doesn’t have enough resolution,” Johnson said.
