What is Giardia?

Giardia is a common zoonotic parasite of mammals, including people, as well as birds and other vertebrates. It lives and multiplies in the intestine and causes acute diarrhoea (think gastro or ‘Bali Belly’) or chronic nutritional disorders resulting in weight loss and tiredness. Giardia exists as a variety of different strains. Some strains are only found in certain species of hosts like dogs, cats and quendas. Strains that affect humans have a wider host range including pets and wildlife.


Giardia Profile

Giardia is a single-celled organism that lives in the small intestine and is found worldwide. The parasite produces resistant cysts that are responsible for disease transmission. The cysts release trophozoites, which are the active feeding stage of the parasite. These multiply and can be free in the bowel or attached by a sucking disc. The cysts are then passed out by infected animals, like dogs and cats, in the faeces.


How is Giardia spread?

Giardia cysts and are found on surfaces, or in soil, food, or water that has been contaminated with faeces. Cysts can survive in water for several months. Infection occurs when the cysts are accidentally swallowed.


Is this a problem for wildlife?

Giardia can be spread from humans, pets and livestock to unique native animals, making them sick. In Australia, studies have found that urban wildlife such as bandicoots (quenda) are commonly infected with Giardia and sometimes with the human strain. The human strain of Giardia has also been found in native freshwater and estuarine fishes.


Did you know:

  • Many people infected with Giardia parasites will not have any symptoms, but can still pass on the parasite.
  • Giardia is more common in quenda in urban areas than quenda in non-urban areas.
  • Giardia is the most common parasite in the gut of domestic dogs.


Download the factsheet ‘Giardia and Wildlife’.