Salmonella Issue Raises Many Questions

A roundtable discussion on salmonella last year yielded three basic themes: * Diagnostic tools for on-farm evaluation of salmonella status need further refinement.* Science-based approaches, yet to be identified, will be needed for successful on-farm salmonella control.* Salmonella control will be a marketing issue domestically and internationally.An industry panel of experts spelled out those themes

A roundtable discussion on salmonella last year yielded three basic themes: * Diagnostic tools for on-farm evaluation of salmonella status need further refinement.

* Science-based approaches, yet to be identified, will be needed for successful on-farm salmonella control.

* Salmonella control will be a marketing issue domestically and internationally.

An industry panel of experts spelled out those themes following the 3rd International Symposium On The Epidemiology And Control Of Salmonella In Pork in Washington, DC.

As the level of understanding of salmonella risk factors increases at both the farm and processing level, management changes may become necessary to reflect this new knowledge.

The complexity of interactions between hogs, their environment and salmonella contamination suggests that multi-factorial and farm-specific controls will be needed.

On-Farm Tools Traditional on-farm diagnostic tools don't adequately detect salmonella carrier animals. This limits the ability to assess risk factors and to control them effectively.

Serologic tests have been used extensively in the Danish industry's salmonella control program. This extensive testing program has been successful in ranking Danish herds based on their potential salmonella loads. Other European Union countries are following the Danes' lead.

Serologic tests suffer from several shortcomings. Most importantly, they serve as herd screening tests and not individual animal tests. This weakens their use in evaluating control schemes.

Their use as herd evaluations is further weakened by the fact that salmonella infections have been shown to be sporadic and self-limiting, seasonal and farm-specific.

Fecal analysis has shown variable results depending on sample size, handling before testing and the testing methods used. These limitations have undermined the value of previous salmonella research as well.

Many times, it appears finishing hogs are infected late in production and that fecal shedding of salmonella from these hogs is the main source of packing plant contamination.

But it's not often that this exposure relates to the serologic status of the herd.

Without a dependable live animal test, it's difficult to tell if hogs testing clean on-farm are truly clean at slaughter or whether they are a possible source of pork contamination. That also makes it difficult to evaluate the effectiveness of on-farm management changes.

In short, serologic tests need to be further refined to be of value in analyzing herd risk factors and control measures, and identifying the link between on-farm salmonella status and meat contamination at processing plants and at retail.

The above examples point to the need for field research to explore a wide variety of diagnostic tools for individual and herd identification of salmonella. By improved tests, national and international programs can be weighed for their potential in reducing salmonella exposure in pork products.

On-Farm Control Internationally, focus has been to improve sanitation and management practices to reduce exposure to salmonella, particularly in grow-finish hogs. All-i n, all-out production, early weaning, sanitation of facilities, rodent control and enhanced biosecurity measures have been proposed as critical control points in a salmonella control program.

Research, however, reveals salmonella infections are the result of a complex interaction of factors including management, environment, hogs and exposure to other animals in the area.

When producers just relied on sanitation and management control practices alone, there were limited results in consistently controlling salmonella problems, according to evaluations.

Denmark leads the way in evaluations because of their intensive surveillance program. A major focus of Danish work centers on the role of feeds and feeding programs on the gut ecology for salmonella. Finely ground and pelleted feeds, warmer environments and poor pen sanitation have been linked to increased levels of salmonella shedding.

Acidification of feeds, coarse grinds and fermentation of liquid feeds have been investigated with some success in reducing excretion of salmonella organisms.

The mechanisms of action are not well understood, but offer opportunities for future reduction strategies.

But sometimes those Danish management strategies don't pan out. Pen sanitation hasn't always been predictive of salmonella status.

Additional management and sanitation strategies need to be identified and clarified as to their roles in successful control programs.

Salmonella In The Environment A better understanding of salmonella serotypes has begun to emerge. Most found in the pig are environmental contaminants and don't cause disease in the pig. They originate from a wide array of sources (dust, soil, rodents, other mammals, birds, etc.) that are not readily quantifiable. Thus, the opportunity for exposure throughout the breeding-finishing spectrum of a pig's life is diverse.

The finishing hog is currently the primary target of interest because it represents the most prominent pathway to the food supply. The status of nursery pigs and the breeding herd don't seem to be predictors of the salmonella status of market hogs. Therefore, their roles in control efforts will be secondary to those for finishing hogs.

As more is learned about environmental contaminants, it's clear their impact is sporadic, unpredictable, self-limiting and difficult to detect because they may only infect small numbers within a group. These exposures of food safety importance often occur late in the finishing period. Earlier exposures may be self-limiting and naturally eliminated in healthy hogs, but serologically detectable at slaughter.

This relationship further demonstrates that diagnostic limitations pose a major hurdle to progress in the understanding of on-farm salmonella ecology and epidemiology.

Marketing Efforts It's certain salmonella control programs will continue to be important for domestic and international marketing efforts.

In Denmark, Sweden and the Netherlands, control programs grew out of food-borne episodes in people.

These programs raise expectations in other countries. Germany recently mandated a program similar to the Danish salmonella reduction program.

While some controversy as to the role of pork in salmonella contamination of foods remains, it is generally recognized in many countries as a significant potential source of food-borne illnesses.

Control efforts by U.S. production and processing industries have been successful in reducing the impact of salmonella on human health.

But salmonella control programs will remain important for the future competitiveness of the pork industry in domestic and international markets.

The pressures for increased food safety will intensify as consumers expect suppliers to raise the quality of products offered.

Salmonella control programs represent one aspect of this increased quality cycle. Implementation will require research at the basic and applied levels to better understand the factors that influence salmonella status on the farm.

As research progress improves these control programs, it creates a win-win opportunity for consumers and producers alike as overall product quality is elevated.