Bearded dragon leads to gravy Salmonella contamination

No, not gravy made from bearded dragons (a type of reptile), but foodborne Salmonella with a link to the reptile.

Reptiles are an important source of Salmonella, which is why standard guidelines recommend that high-risk people (e.g. children less than 5 years of age, elderly individuals, people with compromised immune systems, pregnant women) not have contact with reptiles or have them in the house. A report in Zoonoses and Public Health (Lowther et al 2011) highlights another possible risk.

The report describes a Salmonella outbreak that was traced back to a potluck dinner. Nineteen cases were identified, 17 primary cases (people that attended the dinner) and two secondary cases (household members of people that attended the dinner). Overall, 29% of people that attended the dinner got sick. A further 18 people had some intestinal disease but strictly speaking didn't fit the definition for a case (however it is suspected that they were part of the outbreak). Salmonella subspecies IV (a type mainly associated with reptiles) was isolated from the stool of five people, confirming the occurrence of an outbreak.

As is typical, food consumption history was evaluated. Sixteen of the 17 primary cases reported consuming turkey gravy, which was a statistically higher proportion than that of people who did not get sick. The gravy was made at the private home of a person who didn't attend the dinner. This was the only home of the people involved where reptiles were kept. Two healthy bearded dragons lived in the house, in a terrarium in the living room.

The investigation focused on the reptiles, since the Salmonella strain found is typically associated with reptiles, and the turkey (the source of the gravy) had no evidence of Salmonella contamination based on testing. Samples from the environment of the household where the gravy was made were collected, and two types of Salmonella were identified. One of these Salmonella types (Salmonella Labadi, which was different from the outbreak strain) was isolated from one of the bearded dragons, as well as the inside and outside of the terrarium glass, other terrarium surfaces, surfaces around the terrarium, the bathroom sink drain and kitchen sink drain.

A common question that comes up when people have reptiles and high risk people in the house is "If I don't take the critter out of the cage, I should be ok, right?" Unfortunately, that's not true. Human Salmonella infections have been clearly identified in situations where reptiles don't leave the terrarium because (as was the case here), while the reptile may not leave the terrarium, Salmonella often does.

The person who made the gravy said that the bearded dragons had not been out of the terrarium when food was being prepared. A child was responsible for feeding the reptiles and cleaning the terrarium, and was supposed to use the bathroom for terrarium cleaning. However, it was reported that the reptiles' dishes "might have" been cleaned in the kitchen sink during the the day period when food was being prepared for the party.

The overall conclusion was that this outbreak "probably resulted from environmental contamination from bearded dragon faeces." It's a reasonable conclusion. Even though the same Salmonella strain wasn't found in the reptile, it makes sense because the reptiles were the most likely source of environmental contamination in the household, and that was the most likely source of the foodborne contamination. Reptiles can shed various Salmonella strains and they can shed intermittently. It takes multiple samples over time to get a real idea of the scope of Salmonella shedding, and I assume that one or both of these reptiles were shedding the outbreak strain at some point.

How can something like this be prevented, since the standard recommendation of having high risk people avoid contact with reptiles doesn't apply to this type of situation?

  • Good hygiene practices should be used when handling reptiles and their environments. In particular, there should be proper attention to hand hygiene after contact with reptiles or their cages.
  • Reptiles should not be allowed in the kitchen. Ever.
  • Food and water bowls should not be cleaned in kitchen sinks. Terrariums should not be cleaned in kitchen sinks. Ideally, they shouldn't be cleaned in bathroom sinks either. (If possible they should be cleaned outdoors with a hose.)
  • Good food handling practices are critical. Here, gravy wasn't re-heated to a high enough temperature to kill the contaminating Salmonella. Adequate re-heating would have prevented this outbreak.
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