Giardia in dogs


  • Giardia is a small parasite that attacks the lining of the intestines (guts) and causes severe, watery diarrhoea.
  • Giardia spreads in poo, dogs catch it when they are exposed to infected poo particles (in water, food or the environment).
  • It often takes more than one course of treatment to cure giardia.
  • Humans and other animals can catch giardia.

Giardia explained

Giardia is a tiny parasite that attacks the lining of the intestines and causes very watery, strong smelling diarrhoea.

Giardia spreads by infected poo, so can be caught anywhere infected poo particles lie i.e. infected water or food, infected dogs and the environment. Giardia germs can survive in the environment for months, even once the original poo particles have gone.

Humans can catch giardia so it’s important to wash your hands after cleaning up dog poo or meeting a dog with diarrhoea.


When to contact your vet

Contact your vet if you are concerned your dog has symptoms of a giardia infection, or if they’ve recently had contact with a dog suffering from giardia.

Your vet is likely to ask for a poo sample to help make a diagnosis, so it may be helpful to collect one before the appointment. Watch our video below on how to collect a poo sample from your dog.

Diarrhoea left for too long can lead to dehydration. Book an appointment ASAP if your dog has any of the following symptoms:

  • Diarrhoea for more than 2-3 days
  • Intermittent diarrhoea for 2 weeks or more
  • Young puppy or an elderly dog with diarrhoea
  • Diarrhoea and other health issues
  • Diarrhoea whilst taking medication.

How to collect a poo sample from your dog


To treat giardia, your vet may prescribe:

Many dogs need more than one course of treatment.

If your dog has become unwell because of severe diarrhoea, they may need intensive treatment (e.g. a drip to give fluids directly into their blood stream, injectable medications and careful feeding).


Your dog's diarrhoea should improve a couple of weeks after treatment; however, some dog's need more than one course to cure the infection. Once your dog has recovered from giardia, it’s uncommon for any ongoing problems to develop.

Published: July 2019

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Written by vets and vet nurses. This advice is for UK pets only.

Illustrations by Samantha Elmhurst