Young poultry are very susceptible to Salmonella Enteritidis (SE) infections because of the absence of complete intestinal flora colonization and an immature immune system. This study evaluated the role of passive immunity on the resistance of young birds against early infections caused by SE. The progeny of broiler breeders vaccinated with an oil-emulsion bacterin was compared to the progeny of unvaccinated birds. Efficacy was determined by challenging birds at 1 and 14 days of age with SE Nal Spc strain, phage type 4. After challenge at 1 day of age, the progeny of vaccinated birds presented a significantly lower number (log10) of SE Nal Spc reisolation (P < 0.05) in liver (2.21), spleen (2.31), and cecal contents (2.85) compared with control groups (2.76, 3.02, and 6.03, respectively). The examination of the internal organs, 3 days after infection, revealed that 28% of the birds (7/25) from vaccinated breeders were positive, whereas 100% (25/25) of the chicks derived from unvaccinated birds were positive. Birds challenged at 14 days of age presented a lower number of positive samples compared with those challenged at 1 day of age, and the progeny of vaccinated birds presented statistically lower numbers (log10) of colony-forming units/ml of SE Nal Spc only in the cecal contents compared with nonvaccinated breeder progeny (2.11 vs. 2.94). Age seems to influence the susceptibility of birds to SE infections: in control groups, the number of positive birds at 14 days of age (9/25) was lower when compared with the group infected at 1 day of age (25/25). The number of positive fecal samples of the progeny of vaccinated birds was significantly lower (36) than those of the control group (108) after challenge at 1 day of age. Unchallenged progeny of vaccinated birds presented passive antibodies detectable by enzyme-linked immunosorbent assay (ELISA) up to 21 days of age. On the other hand, antibodies of the control group were detected by ELISA 14 days after challenge. These results show a significant contribution of breeder vaccination by increasing the resistance of the progeny against early SE infections. However, the bacteria were not completely eliminated, suggesting that additional procedures are needed to effectively control SE infections.
Abbreviations: CFU = colony-forming units; dpi = days postinfection; ELISA = enzyme linked immunosorbent assay; Ig = immunoglobulin; Nal = nalidixic acid; SE = Salmonella Enteritidis; Spc = spectinomycin
Inmunidad pasiva de la progenie de reproductoras pesadas vacunadas con una bacterina emulsionada en aceite contra Salmonella Enteritidis.
Las aves jóvenes son muy susceptibles a las infecciones con Salmonella Enteritidis debido a la ausencia de una colonización completa por parte de la flora intestinal y a la inmadurez de su sistema immune. Este estudio evaluó el papel de la inmunidad pasiva en la resistencia de aves jóvenes contra las infecciones tempranas causadas por Salmonella Enteritidis. La progenie de reproductoras pesadas vacunadas con una bacterina emulsionada en aceite fue comparada con la progenie de aves no vacunadas. La eficacia fue determinada por el desafío con la cepa de Salmonella Enteritidis Nal Spec, fagotipo 4. Después del desafío al día de edad, la progenie de aves vacunadas presentó un número significantemente (P < 0.05) menor (log10) de reaislamientos de Salmonella Enteritidis Nal Spec en hígado (2.21), bazo (2.31) y contenido cecal (2.85) cuando se comparó con los resultados obtenidos para el grupo control (2.76, 3.02 y 6.03, respectivamente). La evaluación de los órganos internos 3 días des
