Pre-harvest risk factors for Salmonella enterica in pork production

Salmonella is an important issue to the pork industry worldwide. Although Salmonella has been identified in all links of the pork production chain, there has been increasing focus on the pre-harvest phase (on-farm). Many investigations have been conducted to identify risk factors for Salmonella infections in pigs. In this review, we surveyed the literature to present a compilation of the scientific knowledge currently available about potential pre-harvest risk factors for Salmonella infection in swine populations, and discussed some of the potential fundamental issues associated with this type of on-farm studies. Because of the dynamic relationship between the host (the pig), the agent (Salmonella), and the environment, definitive statements regarding transmission, shedding, and carrier states are difficult. The number of potential sources of Salmonella infections for a swine population is endless, and the pattern of Salmonella transmission and shedding in swine populations is the result of the combination of a variety of factors resulting in a multitude of potential scenarios. Pigs may be infected with Salmonella during any of the production stages on-farm, and as shown in this review, a variety of risk factors may affect the probability of infection. Moreover, between the farm and the abattoir, additional factors can further increase the risk of Salmonella infections. Therefore, at the time of slaughter, the probability of Salmonella infections in pigs results from the occurrence of risk factors on-farm and between the farm and slaughter. Although a variety of risk factors has been reported, the lack of consistency, the methodological limitations, as well as the complex and dynamic epidemiology of Salmonella in swine populations prevent definitive conclusions. Based on the evidence available at the moment, we conclude that pre-harvest Salmonella control programs must be based essentially on strict measures of biosecurity and hygiene, which should minimize the risk of exposure of the pigs to potential infection sources, as well as the persistence of the bacteria in the herd. Moreover, particular attention must be given to the pre-slaughter process of transportation and lairage, where rigorous washing and disinfection programs should be applied. Published by Elsevier Ltd.