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Surveillance of Ontario Pig Farms for Diseases of Public Health Significance


A sample of approximately 100 pig farms representing the wide spectrum of operations in Ontario were involved in this study. Farms were visited at least 3 times over a 2 year time span, and at each visit, blood samples were taken from 30 sows and 30 finisher hogs and 15 manure samples collected from finisher pigs. A management-housing survey was performed at the time of the visit. This information included details about drug use. The samples were used to examine for the presence of micro-organisms or the presence of antibodies to micro-organisms that are of interest from a public health standpoint.
From manure samples, the following disease causing organisms were identified by culture or other means: Salmonella sp, E. coli O157:H7, Yersinia enterocolitica, Balantidium coli, Giardia sp, and Cryptosporidia. From blood samples, the following diseases were evaluated by serological tests measuring the presence of antibodies: Salmonella sp, Swine Influenza virus (including H1N1, H3N2 Colorado and Texas strains), and Toxoplasma gondii. For each pathogen, there were at least a few farms with positive results. This was the first time in North America that E. coli O157:H7 was identified from pig manure.
The presence and prevalence of these diseases were determined and the data were analyzed to evaluate risk factors. For example, the presence of cats on a farm was strong risk factor for herds to be positive for Toxomplasmosis, and the use of all-in/all-out management by site appeared to be associated with a lower risk of finding Yersinia enterocolitica.
More than half the producers participating in this study were using antibiotics as growth promoters in the grower-finisher ration.
Non-pathogenic E. coli that were tested for antimicrobial resistance demonstrated that multiple drug resistance was common but unrelated to on-farm drug use. Importantly, no resistance was found (from the more than 600 isolates tested) against the newer and very important antibiotics like 3rd generation cephalosporins and fluoroquinolones.

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Expected Impact of Project Outcomes on Food Safety in Ontario:
This project has provided information on the presence and prevalence of diseases of public health significance which will allow the industry to plan strategies for controlling these potential problems. Where risk factors have been identified, programs can be implemented to reduce or eliminate the problem. For example, Toxoplasmosis was identified as a problem on a small number of farms. The implementation of a ban on cats in pig barns and feed preparation areas would eliminate this health risk.
If the Ontario industry was to implement an on-going monitoring program with financial rewards or penalties, this project provides a baseline which can be used to determine factors such as number of samples needed to be collected and which tests to use. One conclusion from this work is that further refinement on testing procedures is required. The sensitivity and specificity of many of the tests is less than ideal or not fully understood. <P> For more information, please visit the <a href="; target="_blank">Ontario Ministry of Agriculture, Food & Rural Affairs (OMAFRA) Food Safety Research Program</a>.

University of Guelph
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