How the CDC figured out pet lizards were behind a multistate salmonella outbreak


A pet bearded dragon. (Gerry Melendez/The State/AP)

Since early 2012, more than 130 people in 31 states have been infected by a typically rare salmonella strain. In a recent report, the Centers for Disease Control and Prevention explained how it isolated the likely cause, a type of pet lizard native to Australia. We thought we’d share it since it shows how the CDC works with state health agencies to investigate outbreaks. Here’s how it played out: 

On Jan. 22, the Wisconsin Department of Health Services shared something odd with the CDC. It had noticed a high rate of people infected with salmonella recently who had also been exposed to pet reptiles. Of the 12 people infected in the state since 2012, 10 reported contact with an Australian native lizard known as the pet bearded dragon.

Spurred by Wisconsin’s notification, the CDC began investigating. On March 25, the CDC sent out a questionnaire to the states involved in its investigation to gather more detail from the infected.  Of 31 completed responses, all but four individuals (87 percent) reported contact with reptiles or reptile habitats. In the interviews, 21 people reported contact with a bearded dragon. (For context, about 5.6 percent of households report owning a pet reptile, according to the American Pet Products Association.)

An investigation by the Oregon State Public Health Laboratory confirmed the suspicions: The lab isolated the salmonella strain in samples from a pet bearded dragon and its habitat in the home of an infected individual. Other lab tests have found some of the strain to be antibiotic-resistant.

(CDC)
(CDC)

The particular type of salmonella reportedly behind the outbreak — Salmonella Cotham — is typically rare. On average, fewer than 25 Salmonella Cotham infections are reported nationwide in a given year. But between Feb. 21, 2012, and last Monday, 132 people had been infected in 31 states, represented in the chart to the right and the map below.

The CDC is still investigating, but it says the bearded dragon is the likely cause and it’s identified some breeders from whom the strain may have originated.

You can read more in the CDC’s report on its investigation.

(CDC)
(CDC)
Niraj Chokshi reports for GovBeat, The Post's state and local policy blog.
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