Dynamics of Salmonella, Campylobacter in poultry
Will the same control measures and interventions work for Salmonella and Campylobacter in poultry? Epidemiological studies provide answers.
With Salmonella and Campylobacter performance standards from the Food Safety and Inspection Service (FSIS) now in place, there’s heightened interest in the on-farm dynamics of these potential foodborne pathogens in poultry flocks.
Will the same on-farm control measures and interventions work for both pathogens? Not necessarily, according to one of USDA’s lead scientists in food safety and enteric diseases, because the dynamics of the two pathogens differ.
On-farm dynamics differ
Irene V. Wesley of the National Animal Disease Center in Ames, Iowa, said Salmonella and Campylobacter enter and colonize turkey flocks at different stages of grow-out and react differently to the grow-out environment.
Dr. Wesley presented findings from epidemiological studies conducted by her lab in U.S. turkey flocks, and she also discussed European research on live-production interventions. Following are highlights of her presentation at the Midwest Poultry Federation Convention:
- While Salmonella enters the turkey brooder house in day-old poults and is spread throughout the flock, few Salmonella were isolated when birds reach market age.
- Day-of-hatch poults are free of Campylobacter, but birds are colonized by the third week and remain colonized until slaughter.
- Once in the grow-out house, increased ventilation may be effective in reducing Salmonella prevalence but has minimal impact on Campylobacter.
- Feed withdrawal, crating, transport and holding prior to slaughter do not alter the prevalence of Salmonella. Subtle changes, however, occur in the population dynamics and distribution of Campylobacter.
- HACCP strategies at the processing plant may explain the significant reductions in Campylobacter estimates based on baseline carcass data from 2004 (77.3%) to 2009 (37.1%).
Differing distributions in poults
A study conducted by Wesley and coworkers showed differing times of entry and persistence of Salmonella and Campylobacter into commercial turkey brooder houses (see “Recovery Salmonella and Campylobacter from ceca of turkeys”).
“The first conclusion from our brooder work is that Campylobacter is not present in day-of-hatch turkey poults,” Wesley said. “Campylobacter tends to show up at about 20 days of age, and high prevalence rates persist in flocks all the way to slaughter.
“In contrast, Salmonella is present in about 4% of day-old poults. Salmonella tends to have a very high prevalence during the brooder phase but by the time the birds are slaughtered the prevalence of Salmonella has declined significantly,” she said.
Salmonella in flux during brooding
Wesley said that the lower prevalence of Salmonella (zero to 5%) at the time of slaughter “tends to suggest that birds had outgrown their Salmonella. It also tends to suggest that on-farm management practices might have contributed to significant reductions.”
The researchers also found that the Salmonella variants present in brooder houses changed over time, with some variants disappearing and new ones appearing as brooding progressed at days 5, 20 and 33.
Campylobacter blossoms during brooding
Poults were free of Campylobacter at day of hatch and on day 5 in the brooder house, but there was s tremendous blossoming of Campylobacter at day 20 and 33. And, in contrast to the reductions seen in Salmonella, 84% of the birds still harbored Campylobacter at time of slaughter.
Wesley said research conducted in Europe has focused on a number of promising on-farm interventions for Campylobacter, including the administration of bacteriophages, bacteriocins and caprylic acids.
Bacteriophages have been shown to be very effective in reducing Campylobacter for a period of about five days after administration. Administering bacteriophages close to the time of slaughter might be an effective approach, she suggested. Drawbacks, however, include the fact that bacteriophages are specific to Campylobacter variants and may be expensive.
Bacteriocins, like bacteriophages, are very effective for a short duration – about 24 hours. This suggests their use might be effective close to the time of slaughter. Again, however, cost may be a factor.
One low-tech, and inexpensive, on-farm intervention, which research has shown to be effective in reducing Salmonella, is the changing of boots before entering brooding and grow-out houses.
Another effective Salmonella control is fogging with disinfectants. This is more effective when the fogging occurs while the feeding, watering and brooding equipment are in place in the poultry house.