In-herd prevalence of Salmonella in 25 selected Minnesota swine farms

Allan R Carlson, DVM; Thomas Blaha, DVM, PhD

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Objective: To assess in-herd prevalence of Salmonella and determine the serovar patterns in a sufficient number of swine herds for a long-term, multi-phase study on the infection-contamination-infection cycle of Salmonella.

Materials and methods: 25 Minnesota swine herds were selected for the study. None of the participating farms identified clinical Salmonella as a problem in their operations. Ileocecal lymph nodes of swine from the 25 farms were collected repeatedly at slaughter by bluntly dissecting lymph nodes from the caudal mesentery. These nodes were macerated and cultured for Salmonella.

Results: One or more animals from 16 of 25 farms were Salmonella-positive on the basis of ileocecal lymph node culture at slaughter. The herd prevalence rate was 64%. Overall, 3.69% of animals were Salmonella-positive at slaughter. The percentage of Salmonella-positive animals in each shipment varied from 0% to 33.3%. The total number of different Salmonella serovars isolated from any of the farms varied from one to nine. All Salmonella serovars isolated were non-species adapted, including serovars Agona, Infantis, and Newhaw. Serovar Choleraesuis was not identified.

Implications: Zoonotic Salmonella serovars, which cause only clinically inapparentinfections in pigs, are prevalent in swine herds, and are of concern to the food industry. The pattern of Salmonella serovars on a farm tends to be specific but variable. Prevalence of Salmonella varies greatly not only among farms, but also within farms, from one production site to another, and from shipment to shipment.

Keywords: Salmonella, herd prevalence, in-herd prevalence, sampling strategy

RIS citationCite as: Carlson AR, Blaha T. In-herd prevalence of Salmonella in 25 selected Minnesota swine farms. J Swine Health Prod 2001;9(1):7-10.

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