Changes in the differential leukocyte count of chicks inoculated with Salmonella.

Studies were conducted to determine the effects of Salmonella anatum and S. heidelberg infections on the differential leukocyte counts of baby chickens. Newly hatched broiler-type chicks were inoculated in the yolk sac with suspensions of either S. anatum or S. heidelberg. At 0, 24, 48, and 72 hr after inoculation, blood was taken by heart puncture from chicks of both inoculated groups and from a group of uninoculated chicks. The averages of the leukocyte counts of three or four chicks from each group were used as the blood values for specific time intervals. The six classes of leukocytes counted were lymphocytes, monocytes, juveniles, heterophils, eosinophils, and basophils. The leukocytes classified as juveniles were immature or degenerate heterophils and were found almost exclusively in the infected chicks. Changes in heterophil, juvenile, and lymphocyte counts were affected by both the number of cells in the inoculum (300 versus 3 million cells of S. anatum) and species (S. anatum and S. heidelberg). Infection with either Salmonella species resulted in the development of a severe heterophilic leukopenia, and a significant increase in the percentage of both juveniles and lymphocytes by 48 hr postinoculation. Mortality rate was higher in groups of chicks inoculated with S. heidelberg than in groups given S. anatum.