Reduction of Salmonella prevalence at slaughter in Lawsonia intracellularis co-infected swine herds by Enterisol® Ileitis vaccination

Salmonella spp. remains a wide-spread pathogen among pig herds and its control has major impact on food borne Salmonella infections in humans. The objective of the study was to investigate the influence of an Enterisol® Ileitis vaccination on Salmonella seroprevalence in Lawsonia intracellularis (L. intracellularis) and Salmonella spp. co-infected pig herds under field conditions. This study compared vaccinated and non-vaccinated pigs of consecutive piglet batches, housed on four different finishing units. Prior to study start, endemic field infections of L. intracellularis and Salmonella spp. were confirmed by serology in the nursery and in all finishing units. Field infection of L. intracellularis occurred at the middle of the nursery phase. In total twenty-five batches of finishing pigs were included in the study, pigs were investigated for four (non-vaccinated group, n = 9) or six months (vaccinated group, n = 16). The primary outcome parameter was Salmonella serology (antibody titers) at the end of fattening. Secondary parameters comprised serology for L. intracellularis and performance parameters, including average daily weight gain (g), duration of fattening period (days), feed conversion (kg/kg) and mortality (%). A total of 709 blood samples were assessed, deriving from vaccinated (n = 439) and non-vaccinated finishing pigs (n = 270). Evaluation of the antibody titers demonstrated that vaccination significantly reduced the Salmonella seroprevalence in the finishing pigs on all four farms. The average OD% values were reduced from 32.7% to 13.4% in addition to a reduced variability in the vaccinated pigs compared to the control group. The Salmonella category of all finishing farms improved by at least one category in accordance with the German Salmonella monitoring program. In addition, vaccination had a positive tendency on the average daily weight gain, fattening duration and reduced mortality. In conclusion, this study demonstrates that vaccination with Enterisol® Ileitis has a positive and direct impact on reduction of Salmonella infection in co-infected herds.