SalmonellaVaccination in Pigs: A Review

Abstract

The control of Salmonella enterica in pig production is necessary for both public and animal health. The persistent and frequently asymptomatic nature of porcine Salmonella infection and the organism's abilities to colonize other animal species and to survive in the environment mean that effective control generally requires multiple measures. Vaccination is one such measure, and the present review considers its role and its future, drawing on studies in pigs from the 1950s to the present day. Once established in the body as an intracellular infectious agent, Salmonella can evade humoral immunity, which goes some way to explaining the often disappointing performance of inactivated Salmonella vaccines. More recent approaches, using mucosal presentation of antigens, live vaccines and adjuvants to enhance cell-mediated immunity, have met with more success. Vaccination strategies that involve stimulating both passive immunity from the dam plus active immunity in offspring appear to be most efficacious, although either approach alone can yield significant control of Salmonella. Problems that remain include relatively poor control of Salmonella serovars that are dissimilar to the vaccine antigen mix, and difficulties in measuring and predicting the performance of candidate vaccines in ways that are highly relevant to their likely use in commercial production.

Maternal vaccination as aSalmonellaTyphimurium reduction strategy on pig farms

“…The persistent and frequently asymptomatic nature of porcine Salmonella infection and the organism's abilities to colonize other animal species and to survive in the environment mean that effective control of subclinical Salmonella infection generally requires multiple approaches applied simultaneously, although clinical salmonellosis can usually be markedly improved by vaccination alone, as demonstrated in the current study (Wilhelm et al . ; Wales and Davies ). Vaccination may assist in the protection of animal health, reduction of antibiotic usage, enhancement of food safety as well as reduction of economic losses and environmental contamination associated with faecal waste and run‐off and transmission of Salmonella to other food animal species, such as poultry, by wildlife vectors (Andrés‐Barranco et al .…”

“…There are a number of strategies that may be used when implementing vaccination of pigs against Salmonella (Wales and Davies ). For instance, immunization of sows to protect their offspring (Roesler et al .…”

“…Several studies have evaluated live vaccines for Salmonella Choleraesuis, a serovar that is particularly pathogenic to both pigs and some humans (Schwarz et al . ), but is now rarely reported in Europe (EFSA , Wales and Davies ). The remaining studies have tested an attenuated vaccine for ST. Monophasic variants of S .…”

“…Live vaccines theoretically offer the best option, since they are able to stimulate cellmediated immunity (Mastroeni et al 2001;Haesebrouck et al 2004), but the extent of this may be limited by the attenuation process necessary for licensing, with the vaccine being cleared from the body before slaughter of pigs and nonpersistent in the environment. Vaccination strategies that involve stimulating both passive immunity from the dam (sow vaccination) plus active immunity in offspring (piglet vaccination) appear to be most efficacious, although either approach alone can yield significant control of Salmonella (Wales and Davies 2017). Relatively few vaccination studies with Salmonella have been undertaken under field conditions on pig farms and most of these have been conducted with small numbers of animals (Schwarz et al 2011;Arguello et al 2013;De Ridder et al 2014;Ruggeri et al 2015;Davies et al 2016).…”

Changes in perceptions and motivators that influence the implementation of on-farm Salmonella control measures by pig farmers in England

“…Firstly, Salmonella is seldom associated with clinical disease (Alban and Stark, 2005;Wales et al, 2011;Wales and Davies, 2016) or apparent (perceived) production loss in pigs (Andres and Davies, 2015;Loughmiller et al, 2007), therefore control is believed to benefit public health rather than the farmer who has to implement interventions . Secondly, farmers may be unable to assess the effect of additional control efforts that they undertake (Evangelopoulou et al, 2015).…”