Salmonella is a gram-negative bacteria that can cause the clinical disease salmonellosis in swine. Because Salmonella is often asymptomatic, it’s vital that swine producers mitigate the development and spread of Salmonella infection as early as possible. While pigs of all ages are susceptible to Salmonella, salmonellosis typically occurs in pigs past the weaning stage.
Salmonellosis can be caused by over 2,000 serotypes of Salmonella, only a few of which affect pigs. However, some of the serotypes that can make pigs ill are bacterial zoonoses — meaning bacteria that can also affect humans — such as Salmonella Typhimurium.
Salmonella can act as a foodborne illness and spread through pork products, a problem worldwide and especially in the United States. The CDC estimates 1.3 million Salmonella infections and 420 deaths in the U.S. annually, with an estimated economic burden of $3.7 billion. This makes Salmonella control in pigs a key part of food safety and public health.
This guide will discuss how Salmonella infection is transmitted and how to control the spread in slaughter pig populations while remaining cost-effective.
How does Salmonella spread among pigs?
Salmonella is mainly spread among pigs by fecal-oral transmission. Pigs begin shedding bacteria within minutes of their infection beginning and can continue to shed the bacteria in feces up to five months after their infection ends.
Another means of Salmonella spread is nose-to-nose transmission, as Salmonella can infect pigs’ tonsils and be shed in oral fluids.
How common is Salmonella in pigs?
Studies have found over 2,000 Salmonella serotypes. Although there are many Salmonella isolates, only a few cause salmonellosis in pigs. The most common are Salmonella Typhimurium (a monophasic variant), S. Heidelberg, S. Derby, and Salmonella Choleraesuis.
Salmonella infections are very common in swine. The National Animal Health Monitoring Service determined that more than half of swine herds in the USA had Salmonella in their populations as of 2009. The exact number of Salmonella infections is unclear.
Symptoms of Salmonella in pigs (Salmonellosis)
Salmonella enterica serovar typically occurs in pigs who are eight weeks of age or older. Clinical signs of Salmonella infection in sows, weaners, and growers include
- Pneumonia
- Fever
- Depression
- Decreased appetite
- Dehydration
- Coughing
- Septicemia (ears, nose, and tail congestion)
- Yellowish diarrhea with a foul odor, sometimes containing blood or mucus
- Intestinallesions
- Inflamed mesenteric lymph nodes
When salmonellosis is in its subclinical stage, pigs will appear asymptomatic. In rare instances, pigs might also exhibit nervous signs. Mortality can also occur in the acute stage, although it is rare. Typically, lactating pigs with piglets do not get salmonellosis due to the passive immunity of colostrum.
A pig’s first Salmonella infection does not typically last longer than a week. However, they may get re-infected within three to four weeks or become carriers for up to five months after recovery. The presence of Salmonella can be hard to detect for this reason.
Tips and strategies to manage the cost of Salmonella in pigs
Salmonella in pigs can be costly; treating pigs, containing infected members of the herd, and losing pigs to death adds up. Additionally, identifying the source of Salmonella can be difficult once it’s already present in your pig farm. Here are some strategies to manage the cost and spread of Salmonella in pigs.
Use probiotics in feed
Utilizing probiotics in your feed is one way to prevent an excessive proliferation of Salmonella serotypes. Probiotics target the gut microbiome of pigs, which can help optimize pig production, alleviate stress, and protect against pathogens. Because Salmonella spp. is enteric — meaning it lives in the digestive tract — probiotics can help create an environment that’s unwelcoming to pathogenic bacteria.
Engrain’s eMax feed technologies utilize probiotics to help reduce the occurrence of bacteria like Salmonella and E. coli in swine production.
Closely monitor feed quality
The quality of your swine’s feed can also impact the prevalence of Salmonella. When feed is contaminated with Salmonella, it can spread the bacteria to pigs. To limit Salmonella contamination in feed, pig producers should follow Good Manufacturing Practices (GMP) and the Hazard Analysis Critical Control Points (HAACP) principles.
Ensure you are monitoring the food chain of your feed sourcing. Where possible, use heat-treated feed to kill and/or damage any active Salmonella bacteria. Always store and transport feed hygienically and with as little potential for Salmonella contamination as possible. Additionally, ensure you store feed in a way that wild birds and rodents cannot access.
Ingredient processing plants and feed mills should manage their cooling systems and dust control to prevent contamination between different ingredients, including ingredients potentially contaminated with Salmonella.
Maintain strict biosecurity measures
Biosecurity is the practice of reducing or eliminating exposure to potentially hazardous infectious agents and toxins. Common biosecurity measures to protect the herd include training personnel on preventing Salmonella or other harmful microorganisms, maintaining records of pigs’ health, and controlling the access of persons and vehicles to the establishment.
Another biosecurity measure is the proper and immediate disposal of all pig carcasses, bedding, and feces that are potentially contaminated with Salmonella. All visitors and personnel should wash their hands and change into clean clothes before entering an area with farm animals. Additionally, you should have a biosecurity plan in place to control rodents and arthropods, including regular checks and prevention.
Vaccination is another key biosecurity measure in preventing Salmonella outbreaks. Strategies include vaccination of sows before farrowing, vaccination of piglets during nursing or weaning stages, and vaccination of pigs during the grower or finisher stage. Mothers seem to be capable of passing Salmonella antibodies to their piglets.
Keeping pig facilities sanitary is another important biosecurity measure.
Keep pig facilities sanitary
Ensuring your pig farms are sanitary is another important part of managing Salmonella in pigs. Pig producers should plan their facilities to limit the spread of Salmonella and continue to clean and sanitize these facilities during production.
To plan facilities in a sanitary manner, make sure to choose a location that is far away from wild and rodent populations. The entire grow-out facility should also have adequate drainage. If they don’t, make sure to build a drainage solution to account for wastewater. You’ll also want to use waterproof building materials that are easy to clean and disinfect.
Pens should have controlled entry points with signs indicating restricted entry to keep out unwanted guests – animals or people. Delivery and collection points should also be far from the pig housing and storage to avoid cross contamination.
Keeping pens dry, clean, and well-ventilated is also important in controlling and preventing the spread of Salmonella in pigs. Additionally, always clean and disinfect empty pens or buildings thoroughly before adding new pigs.
Immediately isolate ill pigs
If you closely monitor the health of your pigs, you may be able to detect salmonellosis cases in a timely manner. Look for warning signs such as weight loss and dehydration.
However, it’s important to remember that infected pigs may be asymptomatic.
Serological tests such as PCR and ELISA can analyze for markers of Salmonella in the blood. The serological ELISA test allows producers to differentiate between vaccinations and active infections.
Once you detect a case of salmonellosis, remove and isolate the infected pigs as quickly as possible. Keep all affected pigs in one area and healthy pigs in another, then eliminate traffic between the two areas. Disinfection of the water bowls and pens is critical.
Carefully introduce new pigs
It’s vital to take the necessary precautions when introducing new pigs to your herd to help prevent the spread of Salmonella. When sourcing rearing and replacement pigs, try to source from as few different places as possible. The fewer sources you have, the lesser your chance of farrowing piglets with Salmonella into your herd.
When introducing new pigs to your herd, keep them separate from the rest of the pigs for about four weeks before introducing them. This can give Salmonella a chance to run its course. You can also take fecal samples from pigs to assess for the presence of Salmonella.
Can you treat Salmonella in pigs?
It’s possible to treat Salmonella and nurse infected pigs back to health. However, care and treatment can be costly and time-consuming. Antimicrobials and antibiotics such as apramycin, ceftiofur, trimethoprim-sulfonamide, or gentamicin can be used to lessen the symptoms of the disease and prevent further propagation.
These drugs do not manage the disease in the long term. Additionally, many herds may exhibit antimicrobial resistance, making the drugs less useful. Hence, Salmonella control and prevention are the key factors in protecting your pig herds.
See how eMax Feed Technologies can keep your pigs healthy
As we’ve discussed, it is important to keep pigs healthy and to take measures to prevent contamination with Salmonella. Certain feed or water additives can become routine preventive measures to reduce the herd’s susceptibility to this pathogen.
Engrain’s eMax Feed Technologies can help protect your livestock from bacteria by promoting gut health. Our studies show significant reductions in pathogens such as E. coli and Salmonella with the use of eMax Feed Technologies.
The product is also more cost-effective than other additives, helping you save money and improve your bottom line. Mitigating the presence of Salmonella in your pig farm can also help protect and promote human health as well.
