The same outbreak, the same guinea pigs, seven years later

In December 2017, Colorado reported two Salmonella Enteritidis infections
in people exposed to pet guinea pigs, bought from two stores of one chain,
supplied by a common distributor in California.

The clinical isolates were indistinguishable — and the pattern was **previously
seen in a 2010 multistate outbreak linked to pet guinea pigs.**

Reconstructing seven years

The case definition looked backwards: the outbreak PFGE pattern, closely
related to a guinea pig isolate by sequencing, with **onset on or after 1
January 2015.** State health departments were asked to review recent records
for guinea pig exposure, and the **USDA's National Veterinary Services
Laboratories** was queried for matching isolates from the animals themselves.

One bacterial lineage, in the same animal supply chain, producing human cases
across eight states over two and a half years — and genetically continuous with
an outbreak from 2010.

The sentence the report turns on

**Following the 2010 outbreak, recommendations including environmental
testing were made to the wholesaler regarding Salmonella prevention;
however, the actions were not implemented. Failure to implement recommended
prevention measures might have contributed to recurrence of the outbreak.**

The investigation had already been done. The cause had already been found. The
remedy had already been written and handed over. Nothing in the system required
anyone to act on it, so nobody did, and seven years later the same strain
infected nine more people — median age twelve.

What was done differently

Knowing that recommendations alone had failed once, CDC **produced a document
of prevention measures for reducing Salmonella in guinea pig colonies,
aimed at the pet industry**, and posted consumer-facing content about the
risk.

The recommendations themselves are unchanged in substance:

• To pet owners: hand hygiene
• To distributors and wholesalers: routine diagnostic monitoring of
  guinea pigs for Salmonella, record-keeping to aid traceback, and
  evaluating the husbandry and sanitation practices of breeders

Which is the uncomfortable part. The measures that would have prevented this
are the measures that were recommended in 2010, restated — and still nothing
compels them.

Source: Centers for Disease Control and Prevention, MMWR.