Dog - Giardiasis

What are Giardia?

Giardia are microscopic one celled parasites (Protozoa) that live in the gastrointestinal tract and can cause diarrhoea. They are not worms and have been largely overlooked until relatively recently.

Most dogs infected with Giardia do not have diarrhoea or any other signs of illness. When the eggs (cysts) are found in the faeces of a dog without diarrhoea, they are generally considered a transient, insignificant finding. However, in puppies and debilitated adult dogs, they may cause severe, watery diarrhoea that may be fatal. In a recent survey in London approximately 15% of healthy adult dogs and 30% of puppies were found to be infected.

How did my dog get Giardia?

A dog becomes infected with Giardia when it swallows the immature (cyst) stage of the parasite. Once inside the dog's intestine, this egg (cyst) undergoes several stages of development. Eventually, the dog will pass cysts in the faeces. These cysts remain in the environment and can infect other dogs. They may also be transmitted through drinking infected water.

How is giardiasis diagnosed?

Giardiasis is diagnosed by performing microscopic examination of a sample of faeces. The cysts are tiny and require special techniques for their detection. Occasionally, the parasites may be seen on a direct smear of the faeces. A blood test is also available for detection of Giardia antigens (cell proteins) in the host’s blood. This test is more accurate than faeces examination, but it requires longer to get a result from the laboratory.

How is giardiasis treated?

The drug of choice used for treatment, metronidazole, is an antibiotic-type drug. It is given for 5-7 days. Other drugs are also used if diarrhoea and dehydration occur. If metronidazole is not effective, other treatments are available.

Can humans become infected with Giardia?

Giardia can also cause diarrhoea in people. Children and any adults with any problem with their immune systems are especially susceptible. Therefore, environmental disinfection is important. The use of chlorine bleach, approximately one cup (250 ml) in 5 litres of water, is effective if the surfaces and premises can be safely treated with it. If in doubt, please contact us. Other disinfectant agents are available.