Giardia is sometimes confused with worms because they invade the gastrointestinal tract and can cause diarrhoea. Giardia is a one-celled parasitic species classified as a protozoa.

Most dogs that are infected with Giardia do not have diarrhoea or any other signs of illness. When the eggs (cysts) are found in the stool 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.

Transmission

A dog becomes infected with Giardia when it swallows the cyst stage of the parasite. Once inside the dog's intestine, the cyst goes through several stages of maturation. Eventually, the dog passes infective cysts in the stool. These cysts lie in the environment and can infect other dogs. Giardia may also be transmitted through drinking infected water.

Diagnosis

Giardiasis or infection with Giardia spp. is diagnosed by performing a microscopic examination of a stool sample. The cysts are quite small and usually require a special floatation medium for detection, so they are not normally found on routine faecal examinations. Tests are also available for detection of antigens (cell proteins) of Giardia in the blood or faeces.

Treatment

Drugs are available to kill Giardia and are normally given for five to seven days to treat giardiasis. Other drugs are also used if diarrhoea and dehydration occur.

Can humans become infected with giardia?

Giardia can cause diarrhoea in humans. Symptoms include nausea, fatigue and loss of appetite but some people show no symptoms at all.

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