When it comes to control of salmonella in pork production systems, there is no silver bullet. Each farm presents its own unique problems.
Instead of one magic tool, farm-specific biosecurity and sanitation procedures need to be developed and implemented for every farm.
This is an ongoing process. Unlike common hog diseases such as pseudorabies, salmonella control has no end in sight.
On-farm salmonella control is likely to become a major part of permanent pork quality assurance programs throughout the industry.
The ultimate goal of such programs in the pork chain is not the elimination of salmonella organisms. The goal is to prevent them from being introduced into herds supplying the food chain.
Porcine Salmonellosis Vs. Pig Infections Not long ago, salmonella in pigs referred to an infectious disease of mainly grow-finish pigs. Porcine salmonellosis is caused by the salmonella species or serotype known as cholerasuis. It poses a serious risk to herd health efficiency, increased mortality and morbidity.
However, its impact is declining with efficient treatment and vaccination.
Currently, salmonella more commonly refers to salmonella-contaminated pork as one of the many sources of food-borne diseases in man. Zoonotic salmonella infections are transmissible from pig to man and cause human disease.
Until recently, human salmonellosis has been primarily a concern of poultry products and eggs. But documented salmonella outbreaks traced back to pork have led to concerns that it is a source of human salmonellosis as well.
Salmonella Infections In Humans The rate of food-borne illnesses in the U.S. continued their decline in 1999. But certain types of salmonella rose to their highest level since government started to track it some years ago.
Recent data published by the Centers for Disease Control and Prevention shows infection rate for the major, monitored food-borne agents has declined from 51.2 cases per 100,000 people in 1998 to 40.7 cases per 100,000 people in 1999.
In contrast, the salmonella infection rate rose from 12.3 cases per 100,000 people in 1998 to 14.8 cases per 100,000 people in 1999.
Most healthy individuals infected with a low dose of salmonella don't get sick. However, very young children, elderly people and immuno-compromised persons can develop serious, potentially fatal disease.
The concern is the trend toward increasingly drug-resistant salmonella strains may make treatment of human salmonellosis increasingly difficult.
Pork is not the leading cause of human salmonellosis. Pork ranks below poultry but above beef in rates of infection.
That fact alone is enough reason to do everything possible to decrease the bacterial load of salmonella in every load of slaughter hogs.
Control In Pork It's very important to tell the public that a "salmonella-infected pig" does not mean "salmonella-adulterated pork," per se.
The zoonotic salmonella organism ingested by pigs colonizes only in the tonsils, the gut and the intestinal lymph nodes. The meat remains free from salmonella.
It's through salmonella-containing saliva, tonsil, lymph node tissue and gut contents that infected slaughter hogs are the main means of introducing zoonotic salmonella into pork.
The potential contamination of hog carcasses and the environment at slaughter lead to an increased chance that equipment, personnel and the final product will be contaminated.
At present, from 30-70% of herds are infected with salmonella. This means that one or more of slaughter hogs carry salmonella in gut and lymph tissues.
Fortunately, only 5-10% of these infected herds pose a large risk of contaminating carcasses, tools, equipment and pork products.
As the packing industry gears up their Hazard Analysis and Critical Control Point (HACCP) programs, bacteriological and/or serological monitoring systems will be installed to identify these high-prevalence herds.
Ongoing monitoring of market hogs will lead to segregation of high-prevalence herds from low-prevalence herds at slaughter. The goal will be reduction of cross-contamination during processing.
Producers also need to limit the number of infected market hogs shipped to slaughter through effective, on-farm, salmonella intervention programs.
Farm Interventions Most zoonotic salmonella infections in pigs are subclinical. Traditional tools for detecting food-borne health risks (disease control in livestock and meat inspection at slaughter) fail to identify the risk.
Monitoring programs can detect high-prevalence herds. Salmonella-targeted biosecurity and sanitation programs can reduce the salmonella slaughter load.
Current on-farm epidemiology has shown each farm has a farm-specific pattern of how salmonella organisms are introduced and perpetuated in a herd.
Producers must start their on-farm control programs by analyzing the specific ports of entry (contaminated feed, birds and rodents, which are carriers of a wide variety of salmonella organisms) by which salmonella could enter their herds and the factors that maintain salmonella on the farm (animal flow, contaminated boots, tools, etc.).
These need to be addressed by stringent biosecurity measures. Introduce animals into your herd that come from herds with a salmonella control program.
Only use feed produced under salmonella-targeted good management practices, shower-in or use barn-specific coveralls and boots.
Rodent bait stations should be located around all barns. Rodent-proof all building perimeters, repair buildings to keep out rodents and bird-proof ventilation systems.
Birds defecate into spilled feed, which can infect your herd. Make sure to clean up all feed spills outside barns and in areas accessible to birds or rodents.
Daily management activities are crucial. Use foot baths for entrance to each barn. Restrict changing boots between barns to entry rooms. Follow all-in, all-out pig flow using proper cleaning and sanitation practices.
Use only one properly designed load-out chute per barn. Provide a separate entrance for introduction of new stock and for people.
When possible, don't use connecting hallways to prevent cross-contamination via fecal material.
If rodents inhabit hog buildings, ensure bait stations are placed in rodent-active areas and are maintained.
Use separate tools such as manure scrapers for each barn.
Provide for complete dust and dirt removal as both can be reservoirs of salmonella organisms.
Producers implementing these intervention measures on their farms will reap huge rewards in the marketplace if they partner with production chains that focus on salmonella reduction.