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Molecular-based detection tools offer new power to trace and cut off animal-to-human disease pathways.

It has all the elements of a plot from Crime Scene Investigation (CSI) or similar television detective dramas.

But in this case the focus is not a criminal. Rather, it's Campylobacter – a group of bacteria found in cattle intestines and shed in cattle feces.

"You could call what we're doing 'CSI: Feedlot," jokes Dr. Doug Inglis of Agriculture and Agri-Food Canada (AAFC), who leads a multi-institutional, four-year project to track the movement of Campylobacter from feedlot cattle.

Campylobacter species, particularly Campylobacter jejuni and Campylobacter coli, are one of the most common causes of acute diarrheal disease (campylobacteriosis) in humans throughout the world. But the connection between Campylobacter species originating in cattle and those infecting humans is unclear.

By tracing the movement of Campylobacter species (collectively referred to as "campylobacters") from the feedlot, Inglis and colleagues will generate information that can be used to assess the threat to humans and to develop strategies for reducing that threat.

"Currently, poultry are thought to be the primary reservoir of Campylobacter species infecting humans," says Inglis. "However there are strong indications that cattle are a major source as well. We feel that campylobacters from beef cattle is an emerging issue that we have the opportunity to address in a proactive manner."

For Meristem Land and Science, Inglis took time from the busy study schedule to discuss the project, the issue of cattle-to-human disease threats and the potential of molecular-based tracing tools to help strengthen the bio-security of Canada's beef industry.

Q: Why pursue this major-scale project?
A: We believe campylobacters from beef cattle is an issue we need to get ahead of to ensure the sustainability of the beef industry.

At a global scale, poultry have been viewed as the major reservoir of campylobacters infecting humans, but there's a good chance cattle may also play a role.

For example, here in Southern Alberta, we see a high prevalence of campylobacteriosis in the Chinook Health Region, and it's no secret there is a high density of cattle in this region.

The bottom line is studies of campylobacters from cattle have been relatively limited, so it's difficult to talk with any certainty about the risk posed to humans.

One thing we do know is ignoring the contamination of food and water by Campylobacter and other human-pathogenic bacteria from cattle could in all likelihood severely damage public confidence in the safety of Canadian beef.

The goal of our research is to track the movement of campylobacters from the feedlot, so we can assess the risk and develop ways to reduce that risk. The projects include components to assess bacteria at the feedlot level, including in various areas of the feedlot environment, in the surrounding environment, at the abattoir and even in meat at the retail level. There is also a human health component that includes assessing stool samples from patients suffering from gastroenteritis.

Q: Describe the role and importance of molecular technology
A: The biggest challenge for this type of research is developing effective methods to identify, quantify and track the bacteria.

Campylobacter species are fastidious in their growth requirements, and some species are very difficult, if not impossible, to culture. That makes things difficult, because most of the literature on analyzing bacteria relies on the ability to culture. So for this research, we recognized a new, more sophisticated approach was needed.

In one of our previous studies, funded by the Canada Alberta Beef Industry Development Fund (CABIDF), we developed a series of tools based on Polymerase Chain Reaction (PCR). (For more information on this study, click here.)

Essentially, PCR is a molecular-based method, and it offers a lot of advantages over traditional approaches. It's far more advanced than traditional approaches. This technology is commonly used in forensics to catch criminals, and it holds a lot of potential for investigating many types of human-pathogenic bacteria associated with cattle.

For example, PCR allows us to make exact copies of specific DNA present in cattle feces, and allows us to determine the presence of Campylobacter species.

The PCR method is very sensitive and allows us to detect DNA of campylobacters even if they are present in relatively small numbers. Logistically, it's a great tool for us.

Q: What is the capacity of the PCR tool used in this project?
A: Science is a progression based on new knowledge, and technology is just a series of tools to gain more knowledge.

While traditional PCR tells us a particular bacterium is present, it doesn't tell us how many cells there are, a big thing we needed to know to develop control strategies. With the latest PCR technology we've developed, we've achieved that goal. It not only tells us a particular bacterium is there, but it also tells us how much DNA is present, and thus how many bacterial cells are present in a sample.

That knowledge is critical to developing management strategies. For example, if you're reducing the population of C. jejuni in fecal material from 1000 cells to a few cells, that's a very effective management strategy. However, a PCR tool based on qualitative detection alone would not be able to distinguish those two population densities.

The tool we've developed can potentially be used for detecting any type of bacteria. The process involves developing what are called "primers" – small fragments of specific DNA that allow the tool to amplify DNA of specific bacterial species.

Besides campylobacters, we've expanded our research to incorporate tracking of other bacterial species that may be of significance such as Arcobacter species, which cause diarrhea in humans, and Helicobacter species, which can cause gastric and duodenal ulcers as well as diarrhea.

Q: What are we learning about mitigation approaches?
A: Our current project has become quite broad, to the point that we're examining the transmission of Campylobacter species throughout the beef production continuum. As mentioned, this even includes a study in the Chinook Health Region, where we're using our PCR detection tool to determine the degree to which the bacteria we're investigating are present in stool samples from humans suffering from gastroenteritis. Also, we've just started another big study to develop effective methods of on-farm management. For example, we are studying deactivition of campylobacters in manure and whole animal compost.

We're not only generating data on the degree to which bacterial survive in the environment, but also where and how they are transferred to humans. This information allows us to pinpoint areas where we can cut off that transfer. We're just mid-way through the main, four-year project, so we'll know a lot more over the next couple years.

Currently, most municipalities rely on water treatment as the only step to ensure that campylobacters are killed. When that step fails, a scenario such as what happened in Walkerton, Ont. in 2000 may result; hundreds of people were infected by Campylobacter jejuni and E. coli O157:H7. The campylobacters infecting these people came from cattle manure that a farmer had recently spread on a field. Unfortunately, soon after the manure was applied, a severe rainfall event occurred which caused runoff of the manure containing C. jejuni which contaminated a well from which the town obtained its water supply. The results of this event were devastating.

Obviously it is essential that we prevent occurrences such as what happened at Walkerton, a major focus of our research.

We're currently investigating methods to killing harmful bacteria in the manure before they're spread on to soil, thereby providing a sort of a safety net. Composting works well for killing E. coli cells, and may work for campylobacters as well.

Also, there is the possibility of developing a product that precludes the colonization of the intestinal tract of cattle by these bacteria. We've got a large effort underway on doing just that. Our production continuum research is also aimed at identifying many intervention steps along the line that could be effective in management of the bacteria, whether those steps be on-farm or in the abattoir, etc.

Of course, a major question we attempting to answer is, to what degree are cattle-derived bacteria impacting on human health?

An important aspect of our research is tracking the development and movement of bacteria that possess resistance to antibiotics, which is obviously another essential issue to the beef industry. Over the next several years, there's potential to make a lot of progress in understanding key issues such as how antibiotic resistant bacteria are transmitted to humans, and how we can implement management approaches to help prevent this.

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