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Seroprevalence of Salmonella, Toxoplasma, and Trichinella in pigs raised under different production systems

A Pork Checkoff-funded study1 by the Ohio State University on the presence of Salmonella, Toxoplasma, and Trichinella in pigs raised under different production systems has caught the attention of a few mainstream publications in recent months. The study compared the seroprevalence of Salmonella, Toxoplasma gondii, and Trichinella spiralis in pigs raised in antibiotic-free, outdoor farms and in “conventional” (indoor) production systems in Wisconsin, North Carolina, and Ohio.

The researchers found:

  • 47% seroprevalence of Salmonella (291 of 616 samples), 4.1% prevalence of Toxoplasma (25 of 616 samples) and 0.3% prevalence of Trichinella (two of 616 samples).
  • The highest seroprevalence of Salmonella was found in pigs sampled in Wisconsin (59%), followed by North Carolina (34%) and Ohio (34%).
  • Significantly higher seroprevalence of Salmonella from antibiotic-free herds (54%) than from conventional production systems (41%).
  • Significantly higher seroprevalence of Toxoplasma among samples from antibiotic-free herds (6.8%) than from conventional herds (1.1%).
  • Two Trichinella samples originated from antibiotic-free herds and no Trichinella was found in samples from conventionally raised pigs.

The researchers found no significant association between Salmonella seropositivity and either of the two parasitic pathogens (Toxoplasma and Trichinella), but there was a significant association between seropositivity for Toxoplasma and Trichinella. They suggested this may be due to the fact that both were more commonly detected in antimicrobial-free herds, with no Trichinella detected in conventional herds.


1. Gebreyes WA, Bahnson PB, Funk JA, McKean J, Patchanee P. Seroprevalence of Trichinella, Toxoplasma, and Salmonella in antimicrobial-free and conventional swine production systems. J Foodborne Pathog Dis. 2008;5:199–203. Available at: http://www.ncbi.nlm.nih.gov/pubmed/18407758. Accessed 9 July 2008.

Online database in the fight against respiratory disease

University of Minnesota researchers, funded by the Pork Checkoff, have created the Molecular Bacteriology Laboratory Web site (http://molecularbacteriology.com/database.aspx). This electronic tool will allow veterinarians and producers to design strategies to control respiratory pathogens such as Actinobacillus suis, Streptococcus suis, and Actinobacillus pleuropneumoniae.

To populate the Web tool, researchers developed genotyping techniques for the three bacteria, created genomic fingerprint databases of the different bacterial strains, and organized the databases to include isolation date, geographic area from which a sample was obtained, age of the pig affected by the bacteria, tissue from which the bacteria was isolated, lesions observed in the animals, and other information about each strain, including its antibiotic resistance profile.

Field veterinarians can order the genotyping of these bacteria from field-collected samples. Results will allow them to:

  • Identify prevalent strains causing disease in specific herds,
  • Select strains to be included in autogenous (or universal) vaccines,
  • Identify new virulent strains introduced into the herd, and
  • Track potential sources of these virulent strains.

The results will be used to further populate the Web tool.

In the process of developing the tool, researchers made interesting discoveries about each pathogen. Only a dozen strains of A suis were found among > 100 isolates. Additionally, one of the strain groups was found in virtually all production phases and herds in the study. Researchers suggest that this strain can be used in the development of a successful universal vaccine.

Actinobacillus pleuropneumoniae genotyping can be used to track introduction of new strains into swine herds and not for the development of vaccines. However, genotyping has been used to identify several strains of Actinobacillus species isolated from lungs and with no further identifications.

The S suis database already is being widely used by field veterinarians for selection of vaccine strains. This database has also been important to understand the public health risks S suis represents to the North American swine production systems. In essence, the surveillance system needed to troubleshoot potential cases of human infection is now in place. Researchers describe the tool as a surveillance system that will monitor the genetic variability and epidemiology of these swine bacterial pathogens.

The genomic database for swine bacterial pathogens was presented by Dr Simone Oliveira at the 2008 meeting of the American Association of Swine Veterinarians and is available for consultation at http://molecularbacteriology.com/database.aspx. Dr Oliveira can be contacted by
e-mail at oliv0107@umn.edu.

PRRS research update

The Pork Checkoff put out its summer call for research projects in June 2008, with a deadline of July 15. The summer call included proposals in the areas of pork safety, worker safety, public health, animal welfare, animal science, and swine health. The swine health call included research on porcine reproductive and respiratory syndrome (PRRS).

The US Department of Agriculture-supported PRRS Coordinated Agricultural Project also announced its project funding opportunities directed at PRRS, with a deadline of August 20.

The International PRRS Symposium meeting will be held in Chicago on December 5–6, 2008. Abstract submission deadline was August 25. The Web site (www.prrssymposium.org) has information on registration, lodging, and a program for this year’s meeting.

Worker Safety Reporting Database

The Pork Checkoff launched the Worker Safety Reporting Database this summer. The database was developed with the support of Minnesota State University. The tool is available online and allows pork producers to share safety-precaution suggestions with other producers, while still maintaining the confidentiality of their own business practices. The goal of the tool is to create producer awareness about safety issues in the industry to reduce the number of safety incidents. In practice, the Web-based tool will allow the user to track safety developments on production operations. Users of the Safety Reporting Database are able to:

  • Create a private record of individual accidents,
  • Create a private record of near-miss incidents, and
  • Create reports of safety trends for the pork industry as a whole.

The database is confidential and can be found at https://safetydata.pork.org.