Longitudinal study describing time to Salmonella seroconversion in piglets on three farrow‐to‐finish farms

Abstract

BackgroundPigs are frequently colonised with Salmonella enterica, and this constitutes a major risk for human salmonellosis. The infection can be assessed by the serological response of pigs to S enterica. A longitudinal study was undertaken on-farm to correctly describe this serological response and investigate factors associated with age at Salmonella seroconversion.MethodsThree pig farms and in each farm three successive batches were considered. Per batch, 40 piglets were selected at random from 10 sows (four piglets per sow). Blood was sampled from sows one week after farrowing and from piglets at weeks 1, 6, 10, 14, 18 and 22 and at the slaughterhouse. Salmonella antibodies were detected in serum using a commercial ELISA test. Factors related to farm characteristics, batch management system, porcine reproductive and respiratory syndrome infection, and sows’ Salmonella serological status were recorded to assess their effect on age at seroconversion.ResultsAt week 1 after farrowing, 96.5 per cent of the sows had antibodies against Salmonella. The serological results of piglets at weeks 1 and 6 only were positively correlated with those of the sows. The average age at Salmonella seroconversion was 137±2.2 days (confidence interval at 95 per cent). The first seroconversions occurred from weeks 10 to 14, but most of the pigs (54.6 per cent) were seropositive at the end of the fattening period, with variations between farms and batches (28.9–75.7 per cent). Herd/farm was significantly associated with age at seroconversion.ConclusionThis longitudinal study allowed the authors to follow precisely the evolution of Salmonella seroconversion from maternity to slaughterhouse and confirm the relationship between the seroconversion of sows and serology of their piglets. Moreover, factors related to farm practices and management as a whole are more influential than individual factors (at the pig level) on age at Salmonella seroconversion.

Salmonella Infection in Nursery Piglets and Its Role in the Spread of Salmonellosis to Further Production Periods

“…No differences were found regarding serological OD% values between infected and non-infected piglets (median OD% of 4.7 and 4.8, respectively), these values being similar to those found in piglets of the same age in other studies [ 20 ]. However, on average, OD% values were much lower than those found in the previous study on 4-wo piglets from the same farms (15.9%; [ 16 ]), evidencing the likely significant decay of maternally derived IgGs against Salmonella within the two weeks after weaning [ 7 ].…”

Monophasic Variant of Salmonella Typhimurium Infection Affects the Serum Metabolome in Swine

“…Finally, in this study, only a portion of the infected animals were seropositive after 21 days. Studies have shown that the dynamic of the animal seroconversion is variable and appears to be related to farm practices that primarily affect the time or level of exposure to the pathogen [45][46][47]. However, in the case of our study, these factors could not explain the difference in seroconversion between animals since all pigs were infected at the same time with the same dose of inoculum and were reared under the same conditions in the animal facility.…”

Influence of colostrum supply on Salmonella spp. seroprevalence in piglet rearing and possibilities to increase colostrum production by optimised feeding

“…Similar results were obtained in a follow-up study investigating the Salmonella spp. seroconversion of piglets on three French farrow-to-finish farms (Cevallos-Almeida et al, 2019). Maternal antibodies in piglets could be detected up to ten weeks of age, and the levels measured correlated with those of the sows at the time of farrowing.…”