Salmonella Intervention Strategies and Testing Methods Differ Greatly Between the U.S. and Europe: What are the Implications?
Countries that produce poultry on a large scale have evolved different methods of production, processing, and testing especially with regard to controlling and testing for Salmonella. The implications of these differences will be discussed.
In the U.S., companies are limited as to the types of interventions they may use to control Salmonella in poultry during breeding, hatching, and growout. These limitations are placed on the industry by economic factors, the U.S. Food and Drug Administration, and the shear scale of production. For example in Europe, some countries test all breeder flocks for Salmonella and destroy any breeder flock that is found to be positive. In this way, they have significantly reduced Salmonella to 3-6% on birds coming into the processing facility. This approach is impossible in the U.S., as we produce twice as much poultry in Athens, GA, than is produced in Sweden, where these practices are common. Some countries in Europe use competitive exclusion (CE) to prevent Salmonella colonization of baby chicks. This approach is illegal in the U.S. because the bacterial cultures used to inoculate chicks (which occupy the attachment sites in
the intestine and produce by-products that kill Salmonella) are undefined (the particular species used are not specifically identified). Salmonella vaccines are available in the U.S., but are often cost prohibitive. Because of these limitations, the U.S. poultry industry has placed much more emphasis on eliminating Salmonella in the processing plant, whereas in Europe, all of the effort to eliminate Salmonella is concentrated on the breeding and growout operations.
In the U.S., over 99% of companies use immersion chilling systems. In Europe, air chilling is most commonly used. This is important because immersion chilling is by-far the most effective intervention tool available for poultry processors. In Europe, no chemicals are used to reduce Salmonella during processing, including chlorine. What happens when a flock that is contaminated with Salmonella enters the plant or what happens when the interventions used in the field breakdown? In a word, nothing. The E.U. does not have any Salmonella regulations for poultry carcasses. The E.U. considers Salmonella on carcasses to be a sanitation indicator, not a food safety issue (Dr. Nelson Cox, USDA-ARS).
In the U.S., the USDA-FSIS inspectors rinse a chicken with 400 mL of sterile buffered peptone water (whole carcass rinse). In the EU, they take a 25-gram neck skin composite sample from 3 carcasses and pool them. Cox et al. (2008) conducted a study to the methods of the U.S. and E.U. These researchers found that both methods are fairly equivalent for detecting Salmonella but that neither is sensitive enough to be considered perfect. For example, on many carcasses, the neck skin method picked up the Salmonella, but none was found in the carcass rinse for that carcass and in other cases, the reverse occurred. Based on this study, both methods would need to be used together to really get a good idea of actual prevalence. It is important to note that in some countries around the world, in particular for exported product, the test method is completely different. The chicken skin is sterilized using a blow-torch or iodine solution, then the skin is removed using sterile tweezers and a sample of deep breast muscle is taken and tested for Salmonella. It is interesting that Salmonella is never found using this technique, allowing the
company/country to boldly state that they do not have any Salmonella on their poultry. This is misleading and causes great confusion. By this testing method, a company could say that their chicken is sterile, which is of course, impossible. Meanwhile, the USDA-FSIS is forcing companies in the U.S. that are in Category 2 or 3 to post their Salmonella prevalence, names, addresses, and USDA Plant Numbers (P-numbers) on the internet for the world to see.
Poultry companies in this country are placed in a very difficult situation. They are required to use chemicals in the plants to lower Salmonella to acceptable levels for the USDA. They do an excellent job in this regard. However, because they use chemicals, they cannot export to Europe. Moreover, they cannot use cost effective measures such as CE to control Salmonella during growout because they are too expensive or are against the law due to FDA regulations. Even though they effectively lower Salmonella to 7.5% nationwide on post-chill carcasses, this is not acceptable to countries that have a "zero tolerance" for Salmonella regulation for imported poultry, which is based on an inaccurate testing method. To add to the difficulty, now the companies that are in Category 2 or 3 of the Salmonella performance standard must have their Salmonella data posted on the internet, which eliminates their exportation to "zero tolerance" countries.
An extremely important question that must be answered is, what are the Europeans getting for the incredible expenditure of effort and money trying to eliminate Salmonella from the breeders, hatchery, and growout operation? For example, what impact does this effort have on human salmonellosis? Cox et al. (2008) reported that the total number of people who have salmonellosis is far greater (42.8 per 100,000 people in Sweden versus the U.S. where it is 14.9 per 100,000 people) in a country where extraordinarily expensive measures are used to eliminate Salmonella from the flocks prior to processing. There should be an effort by leaders of these countries to use sound scientific principles to come together and agree on compatible methods for eliminating and testing for Salmonella. There is no logical reason why a method used in the field for many years in Europe to eliminate Salmonella from the flock (competitive exclusion) without any adverse effects, cannot be used in the U.S. This causes great confusion for companies that operate globally and for consumers who believe they are buying "Salmonella free" chicken.
Cox, N. A., L. J. Richardson, J. A. Cason, R. J. Buhr, D. P. Smith, P. F. Cray, and M. P. Doyle, 2008. Comparison of neck skin versus whole carcass rinse for prevalence of Salmonella and E. coli counts recovered from broiler carcasses. Presented at the U.S. Poultry and Egg Association Exposition, Atlanta, GA.
By Scott M. Russell, Ph.D., Extension Poultry Scientist Extension
Poultry Tips (March 2009)
The University of Georgia Cooperative Extension Service
College of Agricultural and Environmental Sciences / Athens