George Charbonneau from South West Ontario Veterinary Services, Looking Upstream For Salmonella Infection

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Human Salmonellosis caused by Salmonella typhimurium and monophasic Salmonella continue to be a food safety concern on a world wide basis. There is a high correlation between the prevalence of Salmonella on pig farms and the levels of Salmonella contamination of carcasses at the slaughter house. Salmonella control mechanisms at the farm level are therefore of major importance. In Europe, a legally prescribed monitoring program provides comprehensive data on the status of pigs in finishing farms at the end of the growing period but less is known about the prevalence of Salmonella in sow farms where piglets are reared.

 

These German researchers wanted to investigate Salmonella prevalence on piglet producing farms by using blood samples and environmental samples. This study included 24 different pig farms that had previously been divided into 12 Salmonella-conspicuous (SC) and 12 Salmonella-inconspicuous (SI) farms on the basis of the serological status of their piglets (25 kg).  The evaluation was based on 498 environmental samples and 2641 blood samples. SC farms were further subdivided into farms with sow vaccination against Salmonella (n = 3) and those without vaccination (n = 9).Maternally derived antibodies for Salmonella normally have almost completely disappeared by the time piglets reach 25 kg. The resulting information would then be used to describe the distribution of Salmonella on the farm, compliance with previous classification into Salmonella-inconspicuous (SI) and Salmonella-conspicuous (SC) farms, as well as effects of sow immunization on Salmonella prevalence in environmental samples and on optical density (OD%) values of the piglets.

 

The researchers found the following:

  • both the highest Salmonella prevalence in the environment and the highest antibody titers of the examined piglets were determined on Salmonella conspicuous farms at both defined time points.
  • piglets from vaccinated sows showed the highest OD% values, before and after vaccination.
  • on Salmonella conspicuous farms, most Salmonella-positive samples could be obtained in rearing areas (2017: 40.8%, 2019: 26.0%).

Take Home Messages:

  • Sow vaccination alone did not sufficiently influence Salmonella prevalence at the farm level.
  • General Salmonella infection pressure at the level of the piglet rearing level seems to play a major role for Salmonella prevalence in the environment and for high OD% values of related pigs.
  • If you have a “downstream problem” with infection in the growing pig it is never a bad idea to look “upstream” to the level of infection pressure in the sow herd.

Ref:  Buch JM, Visscher C, Schulte Zu Sundern A, Schulte-Wülwer J, Deermann A, Holling C.   Prevalence of Salmonella by Serological and Direct Detection Methods in Piglets from Inconspicuous, Conspicuous, and Vaccinated Sow Herds.  Animals (Basel). 2019 Dec 21;10(1). pii: E29. doi: 10.3390/ani10010029.

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