White paper: Clostridium difficile as a Risk Associated with Animal Sources

The white paper summarizes all historical data on C. difficile infections in humans; evaluates epidemiological data on animals, non-animal sources, and foods that have the potential to cause human infections and factors that affect transmission of C. difficile; evaluates hospital acquired C. difficile infections; evaluates worldwide understanding of C. difficile infections and their sources; and identifies the data gaps and discusses how these gaps influence the understanding of C. difficile and proposes tasks needed to close the gaps.

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Objectives

The objectives of the white paper were to:

• Summarize data on C. difficile infections in humans including nosocomial illness, community-acquired infections, and antibiotic resistance
• Summarize data on C. difficile infections in livestock and companion animals
• Evaluate epidemiological data on animals, non-animal sources, and foods that have the potential to cause human infections and factors that affect transmission of C. difficile
• Evaluate worldwide understanding of C. difficile infections
• Identify the data gaps and discuss tasks needed to close the gaps

Conclusions

C. difficile has been a recognized cause of human illness at least since the 1960s and is now the most common cause of diarrhea in health care facilities, contributing to the death of about 14,000 people annually. The normal habitat of C. difficile is the gastrointestinal tract of humans and other animals and large numbers of spores are present in feces. Therefore, transmission occurs by some version of the fecal-oral route. Traditionally most patients were old, taking antibiotics, and/or resident in a healthcare facility. But an increasing number of younger, healthy and non-hospitalized persons have recently become infected. The emergence of hypervirulent strains, newer wide-spectrum antibiotics, and increased exposure to C. difficile outside of healthcare facilities may all have played a role in this changing epidemiology.

To determine if C. difficile in food is a threat to human health, we need more information on:

(a) spore levels in different foods; (b) possibility of growth and toxin production in different foods; (c) stability of toxins at different temperatures or pH values in foods; (d) ability of spores to survive different processing conditions and antimicrobials; (e) C. difficile strains present in animals and food to determine if they are the same as those isolated from human cases

Deliverable

Clostridium difficile has been detected at low levels in meat from seven countries and has been detected in cattle, farmed deer, goats, horses, poultry, sheep, and swine worldwide. Although there has been no definitive evidence that humans have become infected with C. difficile from contaminated meat or exposure to animals infected with or carrying C. difficile, meat producers and processors should be aware that this is a possible route of infection. Sanitary precautions taken in slaughterhouses and meat processing plants to prevent contamination with Salmonella and E. coli will also aid in preventing contamination with C. difficile. However, C. difficile forms resistant spores, so cooking and many food processing methods, effective in killing Salmonella, may not destroy spores if they are present.

Most C. difficile infections in humans still occur in older people taking antibiotics in healthcare facilities. If meat has been a source of human infection, it is not likely a significant source since there have been no outbreaks or cases associated with meat or animals. However, epidemiology of C. difficile has been changing during the past decade. So the meat industry should remain alert for any evidence that C. difficile has become a foodborne infection or has been transmitted to those with occupational contact with animals or meat.