By: Heather Williams

Over and over we hear about how preventative antibiotics, while helpful to the animal at the moment in preventing bacterial infections, can actually have more harmful long-term effects.  The primary issue being antibiotic resistance in humans.  This can occur from a couple of different ways.  First, it could be carried over directly from consuming an animal that has some antibiotic resistant bacteria.   Or it could originate from antibiotics being washed downstream into irrigation or drinking waters from infected animal waste.  Antibiotic resistance is often caused by antibiotics not completely killing all of the bacteria resulting in mutated and resistant bacteria or bacteria mutated to be resistant after being exposed to an inappropriate antibiotic.

Thankfully, the trend is moving towards using prebiotics and probiotics to strengthen the immune system of these food animal in a more natural way and refraining from antibiotic use unless it is absolutely necessary.  This is in response to increased awareness of the risks associated with unnecessary antibiotics used in food animals.

So what options does that leave us with?  Large populations, like what is found in feed lots and large farms, often are at greater risk for spreading disease.  This in not unlike humans.  Schools, camps, cruise ships, and even prisons are known for rapid spread of disease because so many people are located in a small area.  Food animals also have their own sets of diseases in addition to those that can be transmitted to humans.  It’s when these diseases directly impact the consumer, often causing illness to those who eat the tainted food, that the general public pays attention.

One option for protecting both the animal population and the human population is making its way into mainstream.  It is a concept we use routinely to protect ourselves from disease but may not think so much about when the topic of foodborne illness comes up.  Vaccines.

Salmonella Vaccine

We vaccinate ourselves and our family to reduce the risk of communicable diseases like measles, mumps, and flu.  These vaccines generate an immune response so that our bodies can recognize the threat and remove it before it can cause any real harm.  What if we could vaccinate food animals for the pathogens that affect humans instead of using antibiotics.  Scientist at the Agricultural Research Service in Ames Iowa created a vaccine for the types of Salmonella that affects pigs and humans.

Vaccines in animals are fairly commonplace.  But these vaccines generally are focused on illnesses that only affect the animal of interest.  These vaccines reduce communicable diseases between animals, keeping them healthier.  There are already vaccines that protect against some strains of Salmonella in pigs, but they are often insufficient.  Many of the existing vaccines only protect against strains harmful to pigs and do not address the strains that cause foodborne illness in humans.

The new vaccine developed by Microbiologist Shawn Bearson of the Agricultural Research Services Food Safety and Enteric Pathogens Research Unit and Brad Bearson of the Agricultural Research Services Agroecosystems Management Research Unit have developed a vaccine that protects food animals against both animal disease-causing Salmonella infection and human disease-causing Salmonella infection.  Salmonella infection or salmonellosis is the most frequently reported foodborne illness in the United States.

So far, the vaccine is protecting pigs against Salmonella Typhimurium and Salmonella Choleraesuis.  The vaccine has also protected turkeys against Salmonella Typhimurium and the multi-drug resistant Salmonella Heidelberg, the infamous bacterium cited for the 2011 outbreak affecting ground turkey.

These two major strains of Salmonella this vaccine prevents have been responsible for many severe disease and deaths in both humans and animals.  In fact, the strain Salmonella Choleraesuis has been a major source of outbreaks across the globe in the 1980s and 1990s.  This vaccine will prevent a future outbreak from occurring, according to research scientists.  The foodborne strain Salmonella Typhimurium is a major player in human Salmonella infection.

Even though the vaccinated animals will have immunity to the protected strains of the vaccine, meaning the animal has antibodies against the pathogenic bacterium, routine tests to detect Salmonella infections can be performed.  The vaccine is built to be to have “Differentiation of Infected from Vaccinated Animals.”  This allows the produce to distinguish natural Salmonella infection exposure.

More work is being done to determine if the vaccine will protect against other strains of Salmonella.  Researchers believe the vaccine may provide additional protection.  The Agricultural Research Service has filed a patent application for this vaccine technology and continues work on this subject.

Salmonella Facts

Approximately one million foodborne illnesses in the United States can be attributed to Salmonella infection.  This illness is responsible for 19,000 hospitalizations and 380 deaths this year.  Typical symptoms of Salmonella infection include abdominal cramps, diarrhea, and fever.  These symptoms often occur around 12 to 72 hours after infection and can last 4 to 7 days.  While most will recover with only mild discomfort and without treatment, some may experience diarrhea so severe they need to be hospitalized for dehydration.  Others who may be of higher risk, such as the very young, the very old, and those with a compromised immune system could experience additional severe illness such as reactive arthritis or blood infections if the bacteria leaves the digestive tract and enters the blood stream

Salmonella often lives in the intestinal tracts of animals, including birds and people.  People can become infected with Salmonella by eating foods which have been contaminated in some way with animal feces.  Usually foods contaminated with Salmonella are animal products such as beef, eggs, poultry, and milk.  However, any food may become contaminated if it comes in contact with infected animal feces.  Infected food is generally unidentifiable because contamination rarely affects the appearance, smell, or the taste of food.

Salmonella comes in many forms.  In fact, there are over 2,300 serotypes or species of the bacteria.  Salmonella Typhimurium and Salmonella Enteritidis are the most common forms of Salmonella infection in the United States, accounting for half of all human infections.  Salmonella Typhimurium is generally associated with foods from animal origin, while Salmonella Enteritidis is often associated with eggs and poultry.

Additional research is being done by other groups for Salmonella vaccines in humans.  Perhaps one day foodborne illness will be a thing of the past.