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Taking Aim at Microbes on Farm Good Strategy for Food Safety

Just because you can’t see something with the naked eye doesn’t mean it isn’t there.

While that statement certainly doesn’t qualify as rocket science, it is, nevertheless, an important message to heed when it comes to microscopic beings such as harmful bacteria, viruses and parasites that can make animals and people sick.

In a report, “What if we could see germs?” Phil Durst, dairy and beef extension educator at Michigan State University, shares that message with livestock owners as he fine-tunes the focus on harmful microbes, among them E. coli O157:H7, Salmonella, Campylobacter, and Cryptosporidium — all of which can infect animals and people alike.

“Just because we can’t see them doesn’t mean we should manage our livestock as though they aren’t there,” he told Food Safety News. And, while his report focuses on animal health, Durst said it also pertains to food safety.

“Healthy animals are an important step toward food safety,” he said. “With healthy animals, you have limited spread and introduction of pathogens. Ultimately, that has to have an impact on food safety.”

In his report, Durst asks these questions: “What if we could see the invisible on farms? What if we could see pathogens that are shed by animals, get tracked by people, are transferred with other materials, take up residence in pens, and, ultimately, infect another animal? What would we do differently?”

These are important questions for livestock farmers to ask themselves, states the report, referring to the results of research conducted by a team at the University of Pennsylvania School of Veterinary Medicine. In this project (reported in the Journal of Dairy Science, Sept. 2013), a team of researchers, led by soil scientist J.D. Toth, selected 13 dairy farms, varying in size from 41 to 275 cows, in southeast and south-central Pennsylvania. They went in search of five animal-borne pathogens on these farms: E. coli O157:H7, Salmonella enterica, Campylobacter jejuni, Mycobacterium avium, ssp. paratuberculosis (MAP) and Cryptosporidium parvum — many of which can cause foodborne diseases in humans.

Looking for these pathogens in samples of fresh and stored manure, bedding, field soil, stream water and milk filters, they discovered that, on all but one dairy, they could isolate one of these pathogens, and, on 7 of the 13 dairies, they could isolate multiple pathogens.

Of special concern when it comes to food safety, E. coli O157:H7 was found in half of the positive samples and on six of the 13 farms.

And, while Salmonella, Campylobacter and Cryptosporidium were found on fewer farms, at least one of these pathogens was isolated from samples taken from six of the 13 farms.

The researchers also looked for, and found, positive samples of a bacterium that causes a serious cattle disease known as Johne’s Disease on 10 farms and from 20 of the 46 positive samples.

Bottom line, the results of this research project revealed that harmful pathogens on farms can be spread not only to other animals, but also potentially to people.

“This may have serious consequences as E. coli O157:H7 has caused fatalities among infected people,” states the report.

Dairy cows that have been culled from a herd are an important source of ground beef. According to the Cattlemen’s Beef Board, culled dairy cows make up approximately 18 percent, or about 2.1 billion pounds, of the ground beef (sometimes steaks) produced each year in the United States.

Referring to the research project, Durst warns that “to the extent that these farms are typical, it likely means that bacteria and viruses that cause disease are probably present on your farm” — even if you can’t see them.

Durst also warns that “not seeing pathogens” can lead livestock farmers to act as though they don’t exist. With that in mind, he makes it a point to warn farmers that “it makes more sense for us to assume that the pathogens are there.”

He said that even though the farms in the research project were small farms — “almost idyllic” — the researchers still found pathogens there.

“We portray small farms as being healthy, but there can always be a sick animal that can spread pathogens,” he said. “Ultimately, this will have an impact on food safety.”

Daniel Grooms, a professor at the College of Veterinary Medicine at Michigan State University, agreed with Durst that some food-safety problems do start on the farm.

Grooms also teaches classes in a food-safety master’s program, with one of his specialties being pre-harvest food safety.

“If we could see [the pathogens], it would make it easier to control them,” he said, referring to the pathogens that can cause food-safety problems when the animals are milked or butchered. “Any time you have something you can see, it’s easier to convince people about the need to control it.”

He compares the incentive to controlling something you can’t see to controlling something that you can see — an oil leak in your tractor, for example. You know you can’t very well ignore it, and you also know you need to fix what’s causing it. Yet something that you can’t see can be ignored — until, of course, an animal or person gets sick.

When it comes to the dangerous form of E. coli, Grooms said it can be in animals that are perfectly healthy and showing no overt signs of harboring the bacteria. And, he pointed out that that’s true in the case of some other zoonotic diseases as well.

According to the Centers for Disease Control and Prevention, zoonotic diseases are contagious diseases spread between animals and humans. They can be caused by bacteria, viruses, parasites and fungi that are carried by animals and insects. Some examples that have to do with food safety are E. coli and Salmonella, which can end up in an animal’s meat or milk.

Although pasteurization kills pathogens in milk, in the case of raw milk, which isn’t pasteurized, the pathogens can be present in the milk if it has been contaminated by fecal material. And, while the pathogens might be in a cow’s digestive tract and not its meat, those pathogens can contaminate the meat when the animal is butchered.

Grooms also pointed out that whenever you have to use antibiotics to treat a sick animal, a food-safety risk is introduced, both because of possible residues in the animal’s meat or milk and also because of the possibility of antibiotic resistance.

“When we reduce the need of having to treat animals with antibiotics, we reduce some of the food-safety risks,” he said. But he also pointed out that, even with good management systems, there will be times animals will get sick and need to be treated with antibiotics.

“But if we can prevent pathogens like Salmonella from coming onto the farm (from the introduction of sick animals from other farms), we’d never have to treat the animals for that,” he said.

Even so, Grooms emphasized that, while you can reduce pathogens on a farm, you’re never going to eliminate them altogether. “But you can manage them,” he said. “We can do things to help reduce the risk of pathogens being present on a farm that could be a food-safety risk.”

Toth, who led the University of Pennsylvania research team, said that, as a soil scientist, he had been researching pathogen survival on farms.

The research team found that Salmonella can survive for more than a year in field soil and that E. coli can survive at least three months in the soil. There’s always a risk of these being transported off or onto a farm when new animals are brought in or shipped off of a farm, he said.

He said that, even though there are more risks of pathogens spreading from animal to animal or from animal to people on large farms simply because more cows are congregated together, he also said that most large farms have veterinarians on board who serve as “another set of eyes.”

Taking a broader view, he said that farmers are typically good stewards of their animals because it’s in their interest to reduce pathogens on the farm.

Taking aim at pathogens

Durst’s report includes five ways that farmers can reduce the spread of pathogens, which he refers to as “what we cannot see.” The recommendations, developed by Michigan State University Extension, outline steps livestock farmers can take to reduce exposure of pathogens.

This approach — preventing instead of reacting to problems — is similar to the approach embodied in the Food Safety Modernization Act, which primarily covers produce. Another similarity is that one of the act’s proposed rules focuses on on-farm practices.

Here are the five recommendations:

  • Practice biosecurity between farms. Whether you visit another farm or someone comes on your farm after being on another farm, boots and coveralls should be clean and sanitized, tires should be free from manure and any materials (feed, for example) should be free of manure.

“Let’s face it,” states the report, “the carelessness of people, including professionals, leads to transfer of pathogens between farms.”

  • Practice biosecurity within your farm. Keeping different groups of animals separated is the best chance we have to keep pathogens from being transferred between groups. Protect calves from exposure to pathogens shed from cows. Clean boots and clothes, clean equipment and feed are key when working with calves. Isolation and separation from older animals need to be maintained.

Toth found a higher prevalence of pathogens in maternity pen bedding than in calf bedding, which leads to the conclusion that removing calves quickly from the maternity pen reduces the risk of infection.

  • Practice good hygiene on farms. In the University of Pennsylvania study, 73 percent of the stored manure samples were positive for at least one of the five target pathogens, and half of the fresh manure samples were positive. Cleanliness helps reduce exposure to pathogens.
  • Practice personal hygiene. Some of the diseases that cattle can carry can also infect people. It is important that you and your employees who work on the farm practice good personal hygiene. Healthy employees are critical to farm function. Consider providing employees with both training about biohazards and with tools (hand-washing stations, disposable gloves, coveralls, etc.) that actually make a difference in the spread of disease agents.
  • Protect your animals. Vaccination is an important tool that can boost  the protection of animals, but it is not a perfect tool. The vaccine must be handled well, administered to animals that will respond and, in some cases, boostered to strengthen the immune response. As important as vaccination is, it only covers specific pathogens. In addition, we need to feed four quarts of colostrum within two hours of birth, pasteurize milk for calves, reduce stresses, reduce overcrowding and isolate new arrivals.

But Durst emphasizes that these five steps, while extremely helpful, are not the silver bullet.

“We’d have to say that bacteria is not on the farm at all, which would be impossible, so these five steps are not enough in themselves,” he said. “But they are certainly good steps farmers could take to reduce pathogens on their farms.”

He concludes the report by warning livestock farmers that they consistently need to take steps to reduce risk by considering how diseases may be spread, and, by doing that, they’ll be protecting their cattle.

“This must be the concern of everyone working on and for the dairy,” he said. “Let’s open our eyes to the work that needs to be done.”

The whole picture

Durst said his report calls attention to research showing potential problems on farms. But he also said that while farmers do take many of these steps, it’s not always done on a consistent basis “because sometimes we rush.”

“In the rush to get there, we take shortcuts,” he said.

Referring specifically to the important part employees play, he said that some farms provide lunchrooms and places where the workers can clean up before eating, which lowers their risk to exposure through food, which could be contaminated if they don’t have resources such as this.

Some farms also provide work clothing and laundry services.

“The greatest benefit of this,” Durst said, “is that it helps the farm to have healthy employees who won’t spread the pathogens on the farm or somewhere else.”

He also said larger farms tend to have lunch rooms, lockers, and showers.

“It’s an investment that’s spread over more employees,” he said. “Healthy employees are an important part of managing pathogens on a farm.”

Grooms would agree, pointing out that practicing good pathogen control should be a culture throughout the operation — that it’s important for everyone to be ever diligent to reduce the concentration of pathogens anywhere they might be. Cleaning the maternal pens but not the calf pens, for example, leaves a hole in the overall goal of managing pathogens.

“We need to look at this holistically,” he said. “It should be a culture throughout the operation. It’s important for everyone, including the employees, to understand this.”

But when asked if he could foresee the day that dairies and beef operations would be required to take steps such as those recommended by Michigan State University,  he said that regulations, for the most part, are market-driven.

“But that may happen over time,” he said.

Toth, meanwhile, also gives a thumbs-up to the Michigan State University recommendations.

“Any way that you can break the transmission of pathogens is good for animal health and good for food safety,” he said.

© Food Safety News