Reptiles and Salmonella is about as far from a new story as anything on this blog, but talking about it is still worthwhile, because it’s still making people ill. I’ll package two similar stories into one post here.

A recently identified (and likely ongoing) Salmonella outbreak in Canada has been linked to pet snakes and/or feeder rodents. Feeder rodents are rodents (mainly mice and rats) that are purchased to feed pet snakes and other large reptiles. They are usually mass produced and sold frozen. Both feeder rodents and snakes are well known sources of Salmonella.

As of March 19, 70 infections in 8 provinces have been identified involving two different Salmonella types: Salmonella I 4,[5],12:i:- and Salmonella Typhimurium. Diagnosed cases typically represent the minority of actual infections, so I’d guess the real burden of disease is in the hundreds. Infections date back to February 2022, so this has been a long, drawn out outbreak that’s been going on under the radar. The graph below shows the epidemiological curve of the infections:

Ten people have been hospitalized and one has died; 19% of cases have been in kids five years of age or younger. Kids are more commonly affected in these outbreaks because of their increased susceptibility to severe disease, and maybe because of more exposure (e.g. touching the reptiles or their environment and then not washing their hands), and probably also because sick kids are more likely to be taken to a doctor and tested than adults. However, the percentage of young kids affected in this outbreak is actually on the low side compared to many reptile-associated Salmonella outbreaks.

A link to contact with snakes and feeder rodents was identified, but no point source (e.g. a particular vendor for the reptiles or feeder rodents) has been identified.

My guess is that feeder rodents are the problem, since they are mass produced in facilities where widespread Salmonella contamination can develop, and such facilities have been linked to similar outbreaks. The feeder rodents are more numerous than snakes, and are moved across the country more than snakes. It’s harder to see how a common source of snakes would result in an outbreak across so many provinces.

Snake owners that purchase feeder rodents should be aware of the ever-present risk of Salmonella, and Canadian feeder rodent purchasers should pay extra attention right now.

Control measures are pretty basic. Feeder rodents should be considered contaminated items and handled accordingly. Basic infection control measures include:

  • Storing frozen rodents in sealed containers
  • Preventing cross contamination of human food
  • Preventing contamination of general household surfaces, especially those where human food is prepared
  • Paying good attention to hand hygiene after touching feeder rodents (and the reptiles to which they’re fed!)

The other story is one that’s been on my “to-write” list for a while. It’s about a Salmonella Vitkin outbreak in Canada and the US that was linked to bearded dragons (Paphitis et al. 2024). The scale of this outbreak was smaller, but it highlighted some important points and the report describes a nice investigation.

Here are the highlights:

  • Two Salmonella infections were identified in Ontario in June of 2022. Both were in infants and bearded dragons were present in both households. Feeder mice were also present in one household.
  • The strain that was involved, S. Vitkin, hadn’t been seen in Ontario for at least 14 years, so a common source of infection was suspected.
  • This led to a broader investigation of S. Vitkin in Canada and the US. Twelve cases were found in the US between March 2021 and September 2022, across 10 states. Five of those (45%) were hospitalized and 67% were kids less than 1 year of age; 73% reported exposure to bearded dragons.
  • No single breeder of bearded dragons was identified across the US and Canadian cases, but bearded dragons from the two Ontario cases came from the same intermediary supplier.

Bearded dragons have (like most reptiles) been previously linked to human Salmonella infections, so that part is not overly surprising. They’re small, interesting, social reptiles, so they may pose more risk than many other reptile species because they might be handled and socialized more, especially by kids.

The total burden of infection in people from reptiles isn’t well known. Large outbreaks are detected more easily, as are infections with weird strains. Sporadic disease is less likely to be identified and investigated, and infections by more common Salmonella strains would be harder to definitively link to reptiles. So, we probably miss a substantial percentage of reptile-associated infections.

My line about reptiles is the same as it’s always been: They’re interesting critters but are clearly associated with a high risk of salmonellosis. There’s no way to eliminate that risk, so we focus on two things:

  1. Household practices to reduce the risk of exposure, and
  2. Keeping reptiles away from high-risk individuals. That includes kids less than five years of age, people over 65 years of age, pregnant women and immunocompromised individuals.

Saying “the reptile never leaves the cage” is not an adequate control measure when high risk people are in the house. While the reptile may actually never leave the cage, the Salmonella can, e.g. on people’s hands or when contaminated items like food bowls are removed. More information about Salmonella can be found on the Worms & Germs Resources – Pets page.