Spring appears to have finally sprung in earnest in Southern Ontario (although we may still get one more frost on the weekend, so I hear) and people are getting back out into the garden.  An increasingly  popular trend in recent years, particularly this year now that the Obama’s are doing it too, is vegetable gardening.  Lots of people like the idea of growing their own veggies in their own backyard, or perhaps in a community garden plot for city dwellers who still want to get their hands dirty – it’s economical, good for the environment, and the plants can be grown "organically" without the use of chemicals or pesticides.  However, pesticides and garden bugs aren’t always the only things to worry about having on your fresh veggies.  We received the following comment from a Worms&Germs reader:

"…What if veggies get infected with raccoon stool[?] Can eggs be killed after [the] veggie is grown and ready to eat?"

Great question.  The concern in the case of raccoon stool is the eggs of the roundworm Baylisascaris procyonis, which can be passed in huge numbers by a relatively high percentage of raccoons in many regions.  If swallowed, the eggs release larvae which can migrate through the tissues of the body, rarely causing visceral, ocular or neural larval migrans.

The good news:

  • Raccoons like to defecate in the same areas most of the time, usually on a relatively flat, elevated surface (e.g. woodpile).  These areas become raccoon "latrines", and the soil in the area can become very heavily contaminated with roundworm eggs.  The good part is that most raccoons therefore not defecate in your garden.
  • Vegetables cannot become "infected" by the parasite – the eggs cannot be absorbed or otherwise get inside a vegetable, they can only contaminate the parts of the plant that are directly in contact with soil.

The bad news:

  • Even though raccoons may not poop in your garden, they can still track roundworm eggs into the soil on their fur or paws when they come by to explore your crop, so you should always consider soil outside as potentially contaminated.
  • Baylisascaris eggs are highly resistant to disinfectants and chemicals, so they can’t be killed this way.
  • Raccoon roundworms aren’t the only parasites that may be found in garden soil.  Dogs and cats can carry other roundworms (Toxocara spp.) which are also capable of causing larval migrans if swallowed (although infection with these worms in dogs and cats is not nearly as common as infection with Baylisascaris in raccoons).  Cats in particular, unfortunately, do sometimes like digging in gardens and may sometimes use a garden as a litterbox.
  • Soil, particularly if it’s contaminated by the stool of any animal, can also contain many different kinds of bacteria such as Salmonella.  Even if you can somehow protect your garden plot from animals, purchased garden soil and fertilizers may contain or may have come in contact with animal stool somewhere along the way.

So how do you make your garden veggies safe to eat?

  • Wash wash wash: Because Baylisascaris eggs are so difficult to kill, the best thing to do is physically remove them from all surfaces of your vegetables by washing thoroughly to remove all visible dirt before doing anything else.  If you cut into a vegetable before washing it, the soil on the outside can contaminate the inside.
  • Peel peel: Peeling vegetables ensures that all dirt (including any dirt stuck in tiny crevices on the vegetable’s surface, or dirt you may not be able to see with the naked eye) is removed prior to consumption, but it’s still crucial to wash the veggie first (and your hands) before peeling.
  • Cook: From an infection control perspective, it’s best to cook vegetables before eating them.  This actually won’t do anything to Baylisascaris eggs – these have to be removed by washing and peeling – but it does help kill bacteria that either contaminated the veggies out in the garden or that contaminated the veggies during their preparation in the kitchen.  For those of us who like our nice crunchy vegetables, obviously cooking them won’t do, therefore washing and peeling become that much more important.

And, of course, always wash your hands thoroughly with soap and water after you’ve been working in the garden, even if you wear gloves.

In a lot of urban areas, it’s hard to prevent raccoons and other animals from getting into yards and gardens.  There are things you can do to discourage raccoons from hanging around your house, and if raccoons establish a latrine on your property it must be very carefully cleaned up.  For more information on Baylisacsaris, raccoons and cleaning up raccoon latrines, please see our archives.