Changes in the differential leukocyte count of chicks inoculated with Salmonella

Area of Science:

• Avian immunology
• Veterinary microbiology
• Poultry health

Background:

• Salmonella infections pose a significant threat to poultry health and food safety.
• Understanding the immune response of young chickens to Salmonella is crucial for developing effective control strategies.

Purpose of the Study:

• To investigate the impact of Salmonella anatum and Salmonella heidelberg infections on the differential leukocyte counts in newly hatched chickens.
• To analyze changes in specific leukocyte populations and their correlation with infection dose and bacterial species.

Main Methods:

• Newly hatched broiler chicks were inoculated via yolk sac with S. anatum or S. heidelberg.
• Blood samples were collected at 0, 24, 48, and 72 hours post-inoculation for differential leukocyte count analysis.
• Leukocyte populations including lymphocytes, monocytes, juveniles, heterophils, eosinophils, and basophils were quantified.

Main Results:

• Infection with either Salmonella species led to a severe heterophilic leukopenia.
• A significant increase in the percentage of juvenile and lymphocyte leukocytes was observed by 48 hours post-inoculation.
• Juvenile leukocytes, identified as immature or degenerate heterophils, were predominantly found in infected chicks.
• The dose of Salmonella anatum (300 vs. 3 million cells) and the species (S. anatum vs. S. heidelberg) influenced leukocyte count changes.
• Mortality rates were higher in chicks infected with S. heidelberg compared to S. anatum.

Conclusions:

• Salmonella infections induce significant alterations in the differential leukocyte profile of young chickens.
• The observed heterophilic leukopenia and lymphocytosis suggest a complex immune response to Salmonella.
• S. heidelberg appears to be more virulent than S. anatum in broiler chicks, as indicated by higher mortality rates.