A Fort McMurray (Alberta) SPCA shelter has been closed because of a Giardia outbreak. Giardia is an intestinal parasite that can cause diarrhea in dogs (and other species, including people) but can also be found in about 7% of healthy dogs. Giardia infection was confirmed in four dogs in the shelter, which led to the rather aggressive measure of closing the shelter. Shelter personnel suspect that the infection started with one dog, who spread the parasite to some other dogs that were in close contact with it. Giardia is passed in stool and animals get infected by ingesting Giardia oocysts from stool contamination in their environment or water sources.   Shelter personnel speculated that "If [the first dog to be infected] went for a walk with the snow melting, of course there’s lots of little presents underneath the snow, so when she goes for a walk and she steps in, say another dog’s feces, and then licks her paws, she can get it."   It’s pretty unlikely that old feces revealed by thawing snow were the cause, since freezing is a pretty effective way to kill Giardia. More likely, the parasite was brought into the shelter by a healthy dog, considering that a reasonable percentage of dogs are shedding Giardia at any time. Why it spread to other dogs is a different question, as is whether the other animals were sick (with diarrhea) and whether Giardia was really the cause if they were. As with any organism that can be found in healthy animals, it’s hard to say for sure whether Giardia actually caused any disease or whether there was some other cause that wasn’t detected and the affected dogs just happened to be shedding Giardia at the same time.

Giardia usually causes pretty mild disease that gets better on its own or with treatment. Shelter personnel stated "We are in desperate need for help from the public as far as raising funds for medical, because obviously it costs a lot of money to treat the dogs. It’s a lot of money to treat an animal with giardia." It’s actually pretty cheap to treat individual cases, but this makes me wonder whether they are treating all dogs in the shelter. That’s not something I’d recommend because there’s little evidence that treatment of non-diarrheic animals is needed or useful. 

Presumably this outbreak (whether it was caused by Giardia or something else) will end soon, either because of or despite of what was done. You never know if you did something to control the outbreak or whether it just ran its natural course. If it truly was Giardia, I’d be surprised if there are more problems, but resolution of the outbreak won’t change the fact that many dogs that they bring in will be shedding the organism.

Giardia is a cause of diarrhea in people, but we now know that dogs probably play only a minor role in human disease. The type of Giardia that is most often found in dogs is a dog-specific type (Assemblage D) that cannot infect people. Unless these dogs were infected with a strain that can infect people (uncommon but not impossible), there’s no risk to people. Regardless, avoiding contact with stool, especially diarrhea, is still a good idea – for prevention of Giardia and other diseases.