Giardia in Dogs

Giardia is sometimes confused with worms because they invade the gastrointestinal tract and can cause diarrhea. Giardia is a one-celled parasitic species classified as protozoa. Giardia can infect dogs, cats, and sometimes can be passed to humans.

Signs & Symptoms of Giardia

Most healthy dogs infected with giardia will have mild diarrhea. When the eggs (cysts) are found in the stool of a dog without diarrhea, they are generally considered an insignificant finding. However, puppies and debilitated adult dogs that become infected with giardia may have more serious signs, such as watery diarrhea, which can lead to dehydration and death.

Causes of Giardia

Giardia usually live in different kinds of water sources, such as ponds or lakes. If your dog drinks from a contaminated water source, they can become infected with giardia. The parasite is in the cyst stage and once inside the intestine, the cyst goes through several stages of maturation. Eventually your dog will pass the infective cysts in their stool and these cysts lie in the environment and can infect other animals.

Diagnosis of Giardia

Giardia is diagnosed by performing a microscopic examination of a stool sample. The cysts are quite small and usually require a special flotation medium for detection, as they are not normally found on routine fecal exams. Occasionally, the parasites may be seen on a direct smear of the feces. Tests are available to detect the antigens of giardia in the blood or feces. These tests are more accurate than the stool exam, but may require several days to get lab results.

Treatment for Giardia

The typical drug used to kill giardia is metronidazole - a gastrointestinal antibiotic. It is normally given for five to seven days. Other drugs are also used if diarrhea and dehydration occur. If metronidazole is not effective, other medications may be recommended.

Prevention of Giardia

Giardia can cause diarrhea in humans too. If your dog is diagnosed with giardia, environmental disinfection is important. The use of diluted chlorine bleach at 1:32 or 1:16 dilutions (one cup in a gallon of water, or 500 ml in 4 liters of water) is effective in killing the cysts.
Giardia cysts are very susceptible to drying. We recommend thoroughly cleaning your dog’s living and sleeping areas, and then allowing the areas to dry out for several days before reintroducing dogs.