Giardiasis is an intestinal infection in dogs AND humans caused by a microscopic protozoan parasite.
It is not a worm, bacteria, or a virus.

There are seven genotypes, A through G, with dogs being most commonly infected by C and D, cats with F, and humans most commonly infected with A and B. Genotype E and F are rarely reported. Other examples of protozoan parasites that can cause enteric (intestinal) disease are Coccidia, Cryptosporidia and Toxoplasma. The majority of dogs infected with Giardia do not have diarrhea, vomiting, or any other signs of illness.

A dog becomes infected with Giardia when sniffing the cysts from contaminated ground, or by drinking contaminated water. In susceptible dogs, once the cyst passes into the dog's intestines, it goes through a transformation to the trophozoite, or feeding form, and attaches to the intestinal wall to feed. If sufficient numbers are present, clinical signs of damage to the intestinal wall will develop.

These microscopic parasites attach themselves to the intestinal wall and the damage causes an acute, sudden-onset of foul- smelling diarrhea. Giardia infection in dogs may lead to weight loss, chronic intermittent diarrhoea, and fatty stool. The stool may range from soft to watery, often has a greenish tinge to it, and occasionally contains blood. Infected dogs tend to have excess mucus in the faeces. Vomiting may occur in some cases. The signs may persist for several weeks and dogs will generally have noticeable weight loss.

The most common drugs used to kill Giardia is Metronidazole (Flagyl) and Fenbendazole. These drugs are normally given for three to ten days to treat giardiasis. Both drugs may be given in combination if necessary. This combination is usually administered to dogs with refractory diarrhoea (diarrhoea that hasn't responded to treatment). Supportive treatment with other drugs may be needed as supplemental therapy if dehydration or severe diarrhoea is present.

  • It is important to adhere to special hygiene measures if the dog has Giardia - these help to reduce the risk of reinfection.
  • Clean the food bowl and toys regularly and rinse the utensils with boiling water.
  • Ensure fresh drinking water is available every day and also clean the drinking bowl with boiling water.
  • If there are places to drink for the dog in the garden, make them available and refresh every day in a clean drinking bowl.
  • If there are places in the garden or outside on the dog circuit where stale water collects (e.g., in flowerpots, puddles etc), where the dog often likes to drink, this should be made impossible for the dog for the time being to prevent reinfection.
  • Collect the dog stools from the garden and dispose of them. Also, clean the trowel and rinse it with boiling water.
  • Bedding and blankets or all places where the dog stays for long periods of time should be cleaned regularly.
  • Wash your hands thoroughly after contact with the dog - this also applies to other family members and friends. Explain to children in particular why these hygiene measures are important so that they can understand them and adhere to them.

Food - Ideally avoid feeding grains or other high-carbohydrate ingredients. All dry foods require a proportion of carbohydrates, such as starch – it acts as a binding agent in its production and dry food should generally be avoided. It is very important to rebuild the structure of the dog’s gut, especially if the dog has been on chemical medication for Giardia. Depending on how badly the dog was affected by the Giardia, there are also various options for building up the intestinal flora, ie: natural pro biotics, like Protect, and Fortiflora, and a prescription diet - one I cannot recommend after using with a gastrointestinal upset is Hills Gastrointestinal Biome, which worked like a miracle!

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.