Loss of virulence by heterophil-adapted Salmonella pullorum

Area of Science:

• Veterinary Microbiology
• Infectious Diseases
• Bacterial Pathogenesis

Background:

• Salmonella pullorum (SP) is a significant pathogen in poultry, causing substantial mortality and economic losses.
• Virulent SP strains lead to high mortality rates and extensive organ and cecal colonization in young chicks.
• Attenuating SP strains is crucial for developing effective control strategies in poultry farming.

Purpose of the Study:

• To investigate the potential of heterophil passage for reducing the virulence of Salmonella pullorum.
• To evaluate the efficacy of an attenuated SP strain in preventing mortality and colonization in day-old chicks.

Main Methods:

• Eight-times-repeated passage of a virulent Salmonella pullorum (SP-V) strain in chicken heterophils was performed.
• The resulting attenuated strain (SP-A) was administered to day-old chicks at doses of 10(7) or 10(8) colony-forming units (CFU).
• Mortality, internal organ colonization, and cecal colonization were assessed 10 days post-administration.

Main Results:

• The virulent SP-V strain caused 64% mortality and 89% colonization of internal organs and ceca.
• The attenuated SP-A strain was nonlethal and significantly reduced internal organ colonization to 4.3%.
• Cecal colonization was completely eliminated (reduced to 0%) in chicks treated with the SP-A strain.

Conclusions:

• Repeated heterophil passage is an effective method for attenuating the virulence of Salmonella pullorum.
• The developed attenuated SP-A strain shows promise as a potential vaccine candidate for controlling pullorum disease in poultry.
• This approach offers a viable strategy for reducing the impact of Salmonella pullorum in commercial poultry operations.