A variety of potential enteropathogens of both animals and humans were identified in the commercially available raw diets evaluated in this study. While adequate information regarding the health risks associated with feeding raw diets is currently lacking, scientific and anecdotal reports suggesting a risk are on the increase (12). Concerns regarding infectious disease associated with raw diets involve both animals and humans. For animals, the issue is exposure to enteropathogens with the possible development of disease, particularly salmonellosis and clostridial diarrhea. For humans, the risk of exposure to pathogens via direct or indirect contact with animal feces, or via contact with raw diets, must be considered, particularly with Salmonella spp., as fecal shedding of Salmonella spp. present in diets has been identified in dogs (6,11).
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Coliform numbers in food samples are used as an index of sanitation (16). The coliform level in all diets was in excess of the maximum allowable level of 1000 CFU/g for raw meat set by the Canadian Food Inspection Agency (17). The presence of E. coli and other coliforms in food samples most likely indicates fecal contamination (18,19); however, contaminated equipment or incorporation of meat from animals with E. coli bacteremia or septicemia could also be a cause. Enterohemorrhagic E. coli O157 is a cause of serious illness in humans, who can be infected with a dose of as few as 10 organisms (20). Specific culture for E. coli O157 was not performed in this study; however, the high E. coli levels identified here and identification of this organism in a homemade raw diet in a previous study (9) suggest that raw pet foods may present a risk to humans. The risk of disease in dogs and cats from exposure to E. coli in food is unclear; however certain strains of E. coli are recognized enteropathogens in these species (21).
Isolation of Salmonella spp. from 20% of raw diets was of concern, but it was not surprising, based on earlier reports. Salmonella sp. is a recognized pathogen of a variety of species, and salmonellosis has been reported in dogs and cats fed raw food contaminated with Salmonella spp. (7,11,12). Subclinical fecal shedding of Salmonella spp. by dogs fed raw diets has also been reported (6,11), creating the possibility of zoonotic transmission of disease via direct contact or through environmental contamination within households. Salmonella spp. can also be isolated from certain raw meat products intended for human consumption. In one study, Salmonella spp. were identified from 7.5% of ground beef, 44.6% of ground chicken, and 49.9% of ground turkey samples (4). The high prevalence of Salmonella spp.contamination of meat intended for human consumption should not be used as a reason to dismiss the significance of its prevalence in raw pet diets, because meat for humans is cooked prior to feeding.
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There is currently inadequate information regarding the safety of raw diets in terms of both animal and human disease. However, considering the variety of infectious and potentially zoonotic pathogens identified here and in other studies, the potential risks must be taken seriously. Given these safety concerns, the absence of any scientific data indicating beneficial health effects of raw diets, and nutritional deficiencies that have been reported with such diets, it is difficult to recommend their use at this point.