Here in California, many dogs, perhaps even a majority, have some giardia organisms in their digestive tracts. Those are the little critters depicted at right, parasites that can cause diarrhea and intestinal distress.
Those high numbers have probably always been present, but we didn't know it until recently. That's because we used to only look for it when the dog had diarrhea. And now we have all these great new tests that can examine the dog's stool and tell you whether or not any giardia critters have set up housekeeping in his innards.
Which means a whole lot of healthy, normal dogs are getting treated for a condition that wasn't causing them any problems.
Since there is no 100 percent effective treatment for giardia, and a dog may test positive for giardia months or even years after treatment, you can see the problem. What, exactly, are you treating here? And should you?
Many veterinarians seem to take a scorched earth approach to digestive health, which is a really good way to end up with resistant organisms and a dog with chronic diarrhea from the death and destruction of his natural intestinal flora. If a dog is doing perfectly fine, and it's probably impossible to really eradicated these little intestinal hitchhikers, why treat?
On the other hand, asymptomatic giardia can become symptomatic if a dog is stressed, has other digestive illnesses, or even is put on antibiotics for anything, with an accompanying die-off of giardia competitors.
Also, while dog-to-human giardia transmission is surprisingly uncommon, it's not impossible.
My personal approach is not to treat a positive test result, and only treat if the dog has symptoms. My treatment goal is to eliminate the diarrhea, and then do everything possible to restore and maintain digestive health, including probiotics (the product FortiFlora has shown some efficacy against giardia in lab mice; I'm not aware of any that has been tested in canines), herbs known to promote good digestion (I'm a fan of peppermint, chamomile, ginger, and the food herb slippery elm, but there are many others). And I also have found that many dogs with chronic diarrhea problems do much better on a grain-free diet.
When it comes to that first treatment step, however, I prefer to use a veterinary drug that has the best chance to work with the least chance to harm my dog. That would be the drug Panacur (fenbendazole), which is considered a particularly safe drug, with few listed side effects. It also clears up around 90 percent of all giardia cases.
For reasons I can't understand, however, a lot of vets still reach first for a less effective, much more dangerous drug, Flagyl (metronidazole). It's only effective in around 67 percent of cases, and carries some pretty scary side effect warnings, particularly at the fairly high giardia dose.
Some very resistant cases will need both drugs, but for a first line therapy, there's no reason I know of to use Flagyl, and plenty of reasons not to, including the risk of neurological side effects.
There's also a giardia vaccine... you can see what I think of that right here, but in short, the 2006 American Animal Hospital Association Guidelines don't recommend it and neither do I.
Photo: Stock 3-d rendered close up of isolated giardia parasites.