The role that the breeding herd can play in setting up a growing pig population for Salmonella disease has not been well defined. Field studies on Salmonella infection in suckling piglets are few and far between. As you can imagine it is not easy to obtain large numbers of the ideal diagnostic samples such as tonsils or mesenteric lymph nodes from weaned pigs. Most studies rely on rectal swabs. These researchers had access to the intestinal tracts of 495 4 week old weaned pigs that were being sold for human consumption. These pigs came from five Salmonella-seropositive breeding farms.
The findings from this study were as follows:
- prevalence of both infection and shedding was high (≈ 36%) Major serotypes found in piglets included 4,,12:i: (35.4%), Rissen (17.1%), Derby (10.9%) and Bovismorbificans (10.3%).
- In 72.8% of the infected pigs the same serotype was found in mesenteric lymph nodes and feces.
- Significantly higher ELISA OD% values were found in meat juice samples from non-infected piglets compared to infected ones (median OD% of 12.0 and 17.3, respectively; P = 0.002) suggesting some protective effect of sow’s colostrum.
- Salmonella was also isolated from feces from weaned sows contemporary of the slaughtered piglets, and 89% of the serotypes identified in sows were also detected in piglets
- Pulsed field gel electrophoresis analyses showed that 75% of the piglet isolates that were compared to those of sows were related to them, suggesting the circulation of Salmonella strains between sows and piglets.
Take Home Message
- Piglets are an important component of on farm Salmonella maintenance.
- A disease control plan for Salmonella in the growing pig should include an assessment for the potential to reduce infective pressure that arises at the sow herd.
Submitted by Brent Jones, DVM