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PIC Update: Interventions for Reducing Salmonella

A University of Guelph researcher has examined the effectiveness of various interventions from farm


April 2, 2010
By PIC

Topics

In western countries, the most frequent cause of human salmonellosis is
inadequately processed, handled or cooked poultry products.

In western countries, the most frequent cause of human salmonellosis is inadequately processed, handled or cooked poultry products. The approaches used to control Salmonella in broiler chickens vary among regions and countries, and there is currently no mandated control program for broiler production in Ontario or Canada. Surprisingly, the situation with regard to Salmonella control within the Canadian context is rather piecemeal and in the published literature there is little documentation concerning the most relevant farm-to-processing interventions for reducing Salmonella in broiler chickens. 

Before various control options are considered, it is important that the existing research evidence foundation is comprehensively and critically evaluated and well understood. Toward this aim, Dr. Scott McEwen and his research team at the University of Guelph have conducted a systematic review of all English-language papers evaluating the effectiveness of various interventions at both the farm and processing levels.

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Their findings? The majority of primary research focused on Salmonella interventions (748 studies), followed by prevalence (200) and risk factors (30). Four on-farm interventions, including competitive exclusion, other feed and water additives (with the exception of antimicrobials), vaccination and biosecurity, and two processing interventions, namely carcass spraying/dipping, and chilling, were prioritized for rigorous systematic reviews-meta-analysis.

Of the on-farm interventions studied, competitive exclusion was found to be the most common (192 studies), followed by non-antimicrobial feed and water additives (114 studies) and vaccination (69 studies). By contrast, a lack of primary research was observed for biosecurity practices, which are frequently recommended to producers for disease prevention and control. At processing, the most commonly investigated intervention was carcass treatments with a spray or dip (75 studies) followed by carcass chilling (37 studies). Overall, the meta analysis indicated that undefined competitive exclusion products are more effective than defined products at reducing Salmonella colonization in broilers, except for a defined, continuous-flow culture-CF3. A variety of routes, including as an additive to feed and water, were as effective at conferring protection as the most popular route studied, oral gavage. 

Of the feed and water additives, prebiotics such as fructooligosaccharides, sucrose and lactose products showed the most promise with respect to the control of Salmonella infection in broilers. Of the vaccines, a killed S. Typhimurium vaccine showed the most promise, and of the biosecurity interventions, an electrostatic space charger in the hatchery showed promise. At the processing level, carcass treatments with a spray or dip, as well as carcass chilling, resulted in reductions of Salmonella prevalence and concentration. Trisodium phosphate (TSP) and lactic acid (LA) were the most commonly investigated carcass spray and dip treatments and were found to be effective against Salmonella. Immersion chilling with chlorine was the most commonly investigated chilling treatment, and chlorine was found to be an effective chilling disinfectant, although data were wide-ranging, which limits the usefulness of an overall estimate of effectiveness. Overall, the optimal combination of interventions is a blend of on-farm and processing interventions to reduce Salmonella from production to final processing. To read more about this study, please visit www.poultryindustrycouncil.ca .

Featured Researcher
Dr. Scott McEwen obtained his DVM and Doctor of Veterinary Science degrees from the University of Guelph. He is currently a professor in the Department of Population Medicine, Ontario Veterinary College. His research focuses on the epidemiology of foodborne infections in food animal populations, particularly E. coli and antibiotic resistant organisms, but also Salmonella and other pathogens. He has extensive experience in conducting epidemiological studies in several food animal species with respect to bacteria of food safety importance. His research on E. coli O157:H7 and related organisms focuses on the distribution of fecal shedding in cattle, and risk factors for infection in cattle and humans. He and his co-workers are also active in simulation modeling of potential intervention strategies (including vaccination) for this infection on farm and throughout the food chain. His research program in antimicrobial resistance focuses on the determinants of selection and assessment of human health risks. Since 1986 he has taught food safety to veterinary students and graduate students in a variety of degree programs and has been the principal research advisor of over 35 MSc and PhD students. He is author or co-author of over 150 publications in refereed scientific journals and has delivered invited research presentations in 10 countries. He consults on food safety, antibiotic resistance, epidemiology and other veterinary public health matters with a number of governmental and non-governmental organizations in North America and Europe, notably various food animal industry groups, the Alliance for the Prudent Use of Antibiotics, the World Health Organization, the United States Food and Drug Administration, the Public Health Agency of Canada and Health Canada. He chaired Health Canada’s Advisory Committee on Animal Uses of Antimicrobials and Impact on Resistance and Human Health, the World Health Organization’s evaluation of the termination of the use of antimicrobial growth promoters in Denmark, the FAO/OIE/WHO Expert Workshop on Non-human Antimicrobial Usage and Antimicrobial Resistance: Scientific Assessment, and an Expert Advisory Panel to a Judicial Review of Meat Inspection in Ontario.

PIC PICKS
By Tim Nelson, Executive Director

The producer updates have been running very successfully throughout the end of 2009 and first  few months of this year, and we’ve now completed the first cycle.

The next season of producer updates kicks off in late October with Brodhagen (26th) and Mount Forest (27th) and we have a great lineup of speakers for both. Thanks to all our sponsors and to the local groups who come up with the topics for each session. To register for all PIC events, call 519-837-0284 or visit the (easier-to-navigate) PIC website.

Don’t forget Research Day this year, which will focus on Poultry Welfare and will feature local and international researchers who are at the cutting edge of the science, consumer attitudes and political opinions on this controversial issue. The Research Day will be held May 11, starting at 1 p.m., at the Victoria Road East Golf Club in Guelph. We’re all gearing up for the London Poultry Show and I’d like to take this opportunity to invite all poultry producers visiting the show to stop by the PIC booth (113 F) for information on the Biosecurity Outreach Program and discussions about what works and what doesn’t, developing practical solutions to on-farm biosecurity problems- and other exciting PIC initiatives that you can be part of in the coming year. Speaking of which, in the last 12 months, we’ve run five producer updates: the Innovations Conference, Research Day, Golf Day, the London Show and four Science in the Pubs. We’ve produced six fact sheets, five electronic information bulletins (PIC Headlines) and over 20 research reports for Canadian Poultry magazine.  We’ve got lots on the go, and you can be part of it.   If you’d like to know more about what we do, have some suggestions for us, or simply want to find out about joining or participating in PIC activities, come and see us at any time during the show. See you in London!

Pathogenecity of the dominant serotype 8  fowl adenovirus (FAdV) of Ontario
The incidence of inclusion body hepatitis (IBH) in broiler chickens has increased considerably over the years, not only in Ontario but throughout Canada as well, and the number of outbreaks has undoubtedly resulted in severe negative impacts on the chicken industry. The economic losses associated with IBH are due to direct mortality (which could be up to 30 per cent), reduced average weight gain and higher feed conversion, and perhaps in some cases increased condemnation rates.

The number of inclusion body hepatitis case submissions to the University of Guelph Animal Health Laboratory increased from 15 in 2003 to 150 in 2006. However, because of the present state of knowledge (or lack of knowledge) it is difficult to give dollar values to accurately assess the economic impact of IBH. The name of this viral infection comes from the observation of massive deposition of viral components (inclusions) filling the nuclei seen in histological sections of the liver cells of infected birds. These inclusion bodies are characteristic in the diagnosis of the disease. Ultimately the resultant malfunctioning of the liver cells (and maybe other cells) leads to the death of the chickens. IBH is caused by fowl adenoviruses (FAdV, which are medium sized DNA viruses that can survive in the barn and environment for a prolonged period of time. Currently there are no commercial vaccines available against this disease, although an autogenous vaccine is under trial and evaluation.

Toward this aim, Dr. Eva Nagy and her research team at the University of Guelph are studying different aspects of IBH and the virus itself. They have been studying the mechanism(s) of how fowl adenoviruses cause disease, (i.e. viral pathogenesis) and are developing tools for rapid diagnosis of the disease. In this project, they developed a rapid, FAdV-specific, highly sensitive and quantitative method for identifying FAdVs using real-time polymerase chain reaction (PCR) technology and assessed the virus load in tissues of infected birds. Real-time PCR is a modern molecular tool, using fluorescence of amplified DNAs to allow us to identify extremely small amounts of viral DNA in tissue samples. With this method it is possible to detect as few as nine viral genome copies in a sample, making it at least 100 times more sensitive than the conventional PCR.

The research team has also shown that this real time PCR was highly specific, as tissues from uninfected chickens and other viral genomes, such as those of Marek’s disease virus, fowlpox virus and infectious laryngotracheitis virus (ILT) did not produce positive signals. They also demonstrated that in addition to in the liver, high amounts of adenovirus DNA were present in the cecal tonsils for a week after inoculation making this tissue an ideal sample source for the diagnosis of FAdV infection. This assay is an excellent research and diagnostic tool that provides high sensitivity, specificity and rapid post-PCR analyses. For more information on this study, please visit www.poultryindustrycouncil.ca.


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