Hedgehog Salmonella update

I'm just back from vacation (luckily, with no infectious disease stories to write), but now I have to catch up on a few posts. One easy one that was waiting for me in my inbox was about Salmonella and hedgehogs.

I've written before about biohazardous hedgehogs, and more details about the US 2011-2013 multi-state Salmonella outbreak were reported in a recent edition of CDC's Morbidity and Mortality Weekly Reports. The outbreak was identified through recognition of a cluster of infections in people caused by the same, historically rare strain of Salmonella Typhimurium. Finding a cluster of the same strain, especially a rare one, suggests that there might be a common source, so an investigation ensued. Here are some highlights:

  • Twenty people from 8 states (Alabama, Illinois, Indiana, Michigan, Minnesota, Ohio, Oregon and Washington) were affected, although (as is typical) it's almost guaranteed that many more people were affected but not tested.
  • Young people were more often affected, with the average age being 13. The age range spanned from less than 1 year to 91 years of age.
  • Four people were hospitalized and one died.
  • 14/15 (93%) people interviewed reported direct or indirect contact with a hedgehog. That's a pretty strong indication that hedgehogs might be involved, since that number is wildly disproportionate to the percentage of people in the general population that have contact with hedgehogs.
  • Hedgehogs were obtained from various breeders, not from a single source.That's not uncommon since breeders often get animals from other breeders or suppliers and a point-source of infection further up the supply chain is likely.

For some reason, hedgehogs are high risk pets when it comes to Salmonella. High Salmonella shedding rates have been identified in studies of healthy hedgehogs and it's clear that contact with healthy carriers can lead to human infection. Hedgehogs should be considered alongside reptiles in terms of pets that should not be present in high risk households (households with kids less than 5 years of age, elderly individuals, pregnant women or people with compromised immune systems). Hedgehog owners should take care to avoid direct and indirect contact with feces and use good hygiene practices to reduce the risk of infection.

Biohazardous hedgehogs

When I give talks about pet therapy animals, I talk about appropriate and inappropriate animals. On one slide I have a picture of a hedgehog, and I use it as an example of an animal that sometimes makes its way into pet therapy programs, despite standard guidelines to the contrary.  This is a species that raises significant infectious disease concerns because hedgehogs can carry an impressive array of microorganisms that can be spread to humans. A big one is Salmonella.

So, it doesn't come as too much of a surprise that the CDC is reporting a multistate outbreak of salmonellosis associated with hedgehogs. Here are the highlights:

  • Fourteen infections have been reported between December 2011 and August 2012. There are probably many more because in most outbreaks, only a minority of affected people get tested.
  • People have been infected in six states (Alabama, Indiana, Michigan, Minnesota, Ohio and Washington), all with the same strain of Salmonella Typhimurium.
  • All 10 people that were interviewed reported contact with hedgehogs or their environments. Considering the rarity of hedgehogs as pets, that's a pretty good indicator that hedgehogs were the source. The outbreak strain of Salmonella was detected in two households, in areas where the hedgehogs lived or were bathed.
  • No one has died, but three people were hospitalized.
  • As it typical, a large percentage (50%) of affected individuals were children 10 years of age or under.

The fact that this outbreak appears to have occurred over a long period of time and a large geographic area strongly suggests that this might be ultimately traced back to a common breeder or intermediary source. Many small pets like these are mass produced by large breeders and shipped across the country, creating the potential for a problem at a single breeder to have far-reaching consequences in other breeder colonies and in households. This has been shown repeatedly with species like hamsters and mice.

This report doesn't mean that hedgehogs shouldn't be kept as pets. However, hedgehogs do seem to be a higher-risk species than average, and households that include high-risk individuals (e.g. young children, elderly persons, immunocompromised individuals, pregnant women) should probably avoid them. More importantly, the potential for transmission of Salmonella and other pathogens indicates the need for good basic, routine hygiene practices, such as washing hands after handling a hedgehog, keeping them out of the kitchen, not bathing them in kitchen or bathroom sinks, and supervising contact between hedgehogs and kids.