Volume 26-06
15 March 2000

[Table of Contents]

Preliminary Report

HUMAN HEALTH RISK FROM EXPOSURE TO NATURAL DOG TREATS

In August 1999, the province of Alberta reported an increase in Salmonella Infantis cases. The initial investigation conducted by the regional public-health authority of Calgary, Alberta, demonstrated that eight of 12 S. Infantis cases were dog owners, and that nine of 12 had had exposure to pig ear dog treats. A pig ear treat taken from the home of one of the cases was also found to be positive for S. Infantis with the same phage type and pulsed-field gel electrophoresis (PFGE) pattern as found in cases. Subsequent investigation of the implicated processing plant indicated the presence of a variety of Salmonella serotypes on finished product including pig ears, as well as other dried pet treats processed in the same manner in the plant.

Both provincial and federal public-health authorities became involved in the investigation with knowledge that the implicated plant distributed product across Canada and to the United States. A national survey of S. Infantis cases was conducted using a questionnaire requesting information on exposure to dog treats. The survey revealed that cases from other parts of Canada had also been exposed to pig ears. (PFGE) patterns from the isolates of many of these cases were the same patterns as detected in the Calgary cluster. A matched case-control study involving 21 cases and 40 controls demonstrated a statistically significant increase in the risk of salmonellosis with exposure to pig ear treats.

It is not clear from the investigation whether cases contacted S. Infantis directly from handling the pig ears, or as a result of the shedding of the organism into their home environments from their asymptomatic pet dogs. One case did not have contact with a dog, but had handled pig ear treats while in a pet store. Only five of 27 dogs owned by cases exposed to pig ears were reported to be ill; however, S. Infantis is not normally considered a canine pathogen. The human health risk posed by pets infected with human pathogens is well documented^(1,2), as is the risk from environmental exposures^(3,4).

The importance of this health risk to humans is underscored by the fact that, in Canada, the pet treat industry is self-regulated; hence, no government regulatory body is responsible for ensuring the safe practice of this industry. The risk is not restricted to the product of only one manufacturer nor to manufactures in Canada alone. Pig ear pet treat product from Canadian and American producers have, since this investigation, also tested positive for Salmonellae. Among the serotypes isolated from pig ear pet treats was a multiple antibiotic resistant strain of S. Typhimurium DT104.

The results of these investigations indicate that pet treats derived from animal parts should be considered a public-health risk if not appropriately processed. In response to the outbreak and because the risk of salmonellosis from exposure to these products was previously unknown, public warnings and health advisories were issued by some provinces and Health Canada. Furthermore, a number of plant investigations have led to as many as 10 voluntary recalls of natural pet products which have been facilitated by the Canadian Food Inspection Agency. Laboratory testing of pet treats is currently being carried out nationwide and similar studies are under way in the United States and Europe as a result of the Canadian investigation and findings.

The pet treat industry has met with federal, provincial, and territorial public-health officials to discuss the problem and is currently in the process of creating a venue for safe standards development and standards sharing.

References

1. Williams-Smith H. Salmonella food poisoning in human beings. The part played by domestic animals. Roy Soc Health J 1969;89:271-76.

2. Plaut M, Zimmerman EM, Goldstein RA. Health hazards to humans associated with domestic pets. Annu Rev Pub Hlth 1996;17:221-45.

3. Haddock RL, SanNicholas A. Infant salmonellosis: vacuum cleaners used to investigate an outbreak. J Environ Health 1989; 52:106-07.

4. Schutze GE, Sikes JD, Stefanova R et al. The home environment and salmonellosis in children. URL: http://www.pediatrics.org/cgi/content/full/1/e1. Date of access: February 2000

Source: The Laboratory Centre for Disease Control, Health Canada, on behalf of the federal, provincial, and regional investigation team; provincial public-health authorities and laboratories for the provinces of British Columbia, Alberta, Saskatchewan, Manitoba, Ontario, Quebec, Nova Scotia, Prince Edward Island and Newfoundland; Calgary Regional Public Health Authority; Food Directorate Guelph Laboratory; Canadian Food Inspection Agency.

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