Immunoprophylaxis of Salmonella gallinarum infection by Salmonella enteritidis-immune lymphokines in broiler chicks

Abstract

Research on the control of intestinal and tissue colonization of breeder and table-egg producing flocks by invasive Salmonella enteritidis (SE) has focused on the advancement of anti-salmonella feed additives, microbiological strategies, and the development of vaccines. Recent investigations in our laboratories have concentrated on the development of immunoprophylactic measures to control Salmonella infections. We have found an increased resistance to Salmonella enteritidis (SE) organ infectivity in chickens conferred by the prophylactic administration of SE-immune lymphokines (SE- ILK). Fowl typhoid, caused by Salmonella gallinarum (SG), is a septicemic disease of domestic birds resulting in morbidity with moderate to very high mortality within the first 2 weeks of age. The objective of the present studies was to evaluate the effect of a prophylactic treatment of neonatal broiler chicks with lymphokines derived from S. enteritidis (SE)-immunized chickens (SE-ILK) on the birds' resistance to an experimental infection with S. gallinarum (SG). On the day-of-hatch, chicks were intraperitoneally administered either SE-ILK, control nonimmune lymphokines (NILK), or nothing. Thirty min later, all chicks were gavaged with either 10 4 cfu or 10 6 cfu SG. For 10 days after challenge, the chicks were observed twice daily for morbidity and mortality. Chicks that died during the experiment had their livers cultured for SG. Chicks that survived throughout the 10 day experimental period were killed and their livers, spleens, and cecal tonsils cultured for SG. The prophylactic treatment of chickens with SE-ILK induced significant protection against an extraintestinal SG infections when compared to NILK as evidenced by: 1) a significant reduction (P < 0.005) in the mortality of chicks challenged with either 10 4 and 10 6 cfu SG; 2) increased average weight gains of chicks challenged with either 10 4 and 10 6 cfu SG; and 3) a significant (P < 0.001) reduction in the total number of SG-organ- culture positive chicks. The results suggest that the prophylactic administration of SF-ILK can non-specifically confer protection to chicks against a pathogenic salmonellae as seen by reduced morbidity, mortality, and organ infectivity of SG in broiler chicks while enhancing weight gain during the first ten days of life.