Did you know that Giardia is the most common intestinal parasite found in humans? It’s true! Giardia can also affect dogs, causing diarrhea, vomiting, weight loss, and loss of appetite. Giardia can also infect dogs that show no signs at all.

Giardia is a parasite that must be ingested to be transmitted. It is most often found in moist environments. Giaridia lives in lakes, rivers, streams, and ponds, and can also be lurking in poop from an infected animal.

If giardia is suspected, your veterinarian will want to test your dog. Giardia is diagnosed by checking a fecal sample: different life stages of the parasite can be seen in a fecal smear on the microscope. There are other tests available, but a simple fecal exam is the best test.  Sometimes, a giardia infection can be considered ‘occult’ or ‘hidden’. These are infections where the parasite is not found in a fecal sample, but the dog (or person!) is still infected with the parasite.

When giardia is diagnosed or suspected, the treatment is an antibiotic called metronidazole, trade name Flagyl. Unless a dog is very sick and dehydrated, which can happen in very young or very old dogs, the treatment is outpatient, meaning that your dog can be treated at home. Sometimes, a veterinarian will also prescribe a bland diet and a probiotic to help the gut heal more quickly.

Your veterinarian may want to run a second or third fecal exam on your dog to confirm that giardia has been eradicated from his system. If this in the case, be prepared to collect a couple of fecal samples after your pet is feeling better.

Giardia is very contagious, and can be passed from dog to human and vice versa. If you dog has been diagnosed with giardia, it is very important to clean up all feces in the yard, use gloves when cleaning up feces, and wash your hands after. If a dog becomes repeatedly infected with giardia, then a source of reinfection (such as wildlife) in the yard should be investigated. If dogs in a kennel are being reinfected, the whole kennel should be evacuated and sprayed down with a dilute bleach solution.

In the past, a giardia vaccine was available, but this vaccine did not seem to be effective in preventing the disease, and is generally not recommended today.

If you suspect that your dog has giardia, schedule an appointment with your veterinarian right away, as this article is no substitute for appropriate veterinary care.