Longitudinal study on the influence of sow and piglet vaccination on seroprevalence of Salmonella Typhimurium in rearing pigs and at slaughter in a farrow-to-finish production system.

Abstract

Background: Salmonella is widespread in pig husbandry and pork is an important source for human salmonellosis. Surveillance programmes are conducted in many European countries and various management measures are implemented on farm level to control Salmonella. Piglet or maternal vaccination can reduce Salmonella shedding and lower the likelihood of piglet infection. Proper management of risk factors can help to maintain low infection pressure. The aim of the study was to evaluate the effect of sow vaccination and piglet vaccination on Salmonella seroprevalence at slaughter.

Results: Different vaccination strategies were evaluated for their effect on seroprevalences in nursery (serum) and slaughter pigs (meat juice) in a farrow-to-finish production chain tested positive for Salmonella Typhimurium (ST). Antibody levels of four piglet groups from one rearing farm and of pigs from four downstream fattening farms were measured by Salmonella LPS-ELISA in a longitudinal study (UNVAC: no vaccination against Salmonella; PIGVAC: piglets vaccinated twice with an attenuated Salmonella Cholerasuis (SC) live vaccine; SOWVAC-1: piglets born from sows vaccinated twice before farrowing with attenuated ST live vaccine; SOWVAC-2: Piglets from vaccinated sows (ST) which had been vaccinated twice already as a piglet (ST). Results revealed significantly lower ELISA optical density (OD) values (p < 0.05) and fewer serological positive piglets (OD > 40) from groups PIGVAC, SOWVAC-1 and SOWVAC-2 compared to group UNVAC at the end of rearing period. Summarizing results from pigs of all fattening farms revealed that pigs from group PIGVAC had significantly lower ELISA OD values in meat juice samples than all other groups (p < 0.05).

Conclusion: Piglet (SC) and sow vaccination (ST) led to significant reduction in detectable antibodies in a ST positive production chain and thus to reduced likelihood of infection during rearing. The results reflect that vaccination with a live attenuated SC vaccine resulted in cross-protection against ST without producing antibodies detectable by standard Salmonella LPS-ELISA. Summarizing all fattening farms, piglet vaccination reduced seroprevalence at the time of slaughter. In conclusion, sow and piglet vaccination with attenuated live vaccines against Salmonella are good instruments to reduce the infection pressure in the rearing period but need additional management measures to show effect on seroprevalence at slaughter.