Salmonellas are ubiquitous, non-spore forming, facultative anaerobic gram negative bacteria. From more than 2500 identified Salmonella serotypes, only a small portion are commonly found in poultry flocks and poultry products. Some Salmonella species present in poultry, such as S. enteritidis, S. typhimurium, S. hadar, S. virchow and S. infantis are epidemiologically important because they cause infections in humans.
Salmonella in Poultry
The route of contamination is by oral infection followed by colonization of the gastrointestinal tract (involving enterocytes and lymphoid tissue). Soon after colonization, bacteremia is observed, with Salmonella detection in several organs, such as spleen, liver, bone marrow, ovaries and oviduct. Salmonella is excreted in the feces, which constitute an important source of contamination for other birds in a house or other flocks.
In poultry, an age related resistance against Salmonella infections is observed. Factors, such as absence or very naïve intestinal flora and not fully developed immune system favor early age infection. Older birds are less susceptible to infection due to the presence complex and well established flora, which competes for receptors or produce metabolic products (bacteriocins) that inhibit Salmonella growth.
Control of Poultry Salmonellosis
“Keep the Salmonella out of your facilities and increase resistance of the birds.”
General Salmonella control programs involve pre-harvest (on-farm) and post-harvest interventions. The following are some of the pre-harvest interventions common in Salmonella control programs.
- Implementation of biosecurity programs including cleaning and disinfection of facilities and equipment. Salmonella status should be monitored after disinfection.
- Animal proofing the facilities and implementation of pest control programs (against rodents, flies and beetles).
- Hatchery sanitation programs.
- Housing of Salmonella free chickens.
- Chlorination and/or acidification (mineral and organic acids) of drinking water.
- Use prebiotics, probiotics and/or competitive exclusion (Aviguard).
- Heat treatment of feed (pelleting), reaching temperatures between 70°C and 90°C.
- Implementation of vaccination programs.
- In broilers, adequate management of litter quality, ventilation and feed withdrawal programs.
The following, are some post-harvest interventions implemented at the processing plant:
- Pre-Scalding brush system to remove organic material and improves the bactericidal efficacy of chemicals.
- Scalding
▸ Use counter current multi-stage scalders with adequate water flow rates.
▸ Addition of chemicals to the scalders (i.e. acetic, lactic and formic/propionic acids).
▸ Maintain adequate water temperature (53°C to 56°C) to avoid Salmonella multiplication. - Picking
▸ Prevent feather buildup on equipment.
▸ Add chlorine, acetic acid or hydrogen peroxide to the rinse water.
▸ Post-feather removal rinses should be maintained at recommended temperatures - Eviscerating
▸ Establish a regular equipment maintenance and disinfection program.
▸ Use of chlorine (i.e. 20 ppm) for whole carcass rinses. - Chilling
▸ Immersion Chilling (common in the Unites States)
■ If using chlorine, maintain chill water pH between 6.0 and 6.5 at temperatures below 40F with available chlorine content of 1 to 5 ppm.
■ Control of organic material load and use counter-current water flow.
▸ Air Chilling (common in Europe)
■ Since chemical interventions are not allowed, environmental sanitation, cleaning and disinfection of facilities and equipment should be in place.
Poultry Salmonella Vaccination Programs
Commercially available vaccines can be classified as live and inactivated (also known as bacterins). Live vaccines (S. enteritidis and S. typhimurium serotypes) serotypes) stimulate humoral and cellular immune responses, reducing colonization of internal organs and gastro intestinal tract and decreasing fecal shedding. Inactivated (bacterins) vaccines stimulate a strong humoral immune response, inducing high levels of circulating antibodies providing protection against internal organ and reproductive tract (ovary and oviduct) infection but also resulting in high levels of maternal derived antibodies (MDA) into the egg providing passive protection to the progenies or table eggs.
Modern, commercial inactivated vaccines (Salenvac-line) are more immunogenic and provide excellent protection against field challenge because the vaccine strains S. enteritidis and/or S. typhimurium are grown under iron restriction conditions and forced to express outer membrane Iron Regulating Proteins (IRP’s are associated with iron transport) as an extra set of immunogenic antigens inducing a broaderpackage of antibodies.
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Recommended Vaccine
- SALENVAC T
