Giardiasis is a gastrointestinal (GI) syndrome caused by multiple species of a flagellated protozoan
                      parasite that infects many vertebrates including dogs, cats, and people.

                      The parasite is found worldwide and has a wide host range. Giardia exists in the GI tract as a
                      motile trophozoite or a nonmotile cyst. The trophozoites live in the upper small intestine of the dog
                      and are more common in diarrheic stools but are not environmentally resistant. The cysts, which
                      are found in the cecum of dogs, are common in both normal and diarrheic stools, and can survive in
                      the environment for days to weeks. The cysts are considered to be immediately infective.

                      Transmission occurs primarily from exposure to cysts from fecal-oral contact or exposure to cysts
                      on fomites (an object that is not in itself harmful, but is able to harbor pathogenic microorganisms
                      and thus may serve as an agent of transmission of an infection, such as food bowls, dog crates,
                      houses, even an article of clothing) or in contaminated water. Transmission can also occur from
                      ingestion of trophozoites in diarrheic stools.

                      After oral exposure to cysts, gastric and duodenal secretions trigger the release of trophozoites.
                      The parasites inhibit host enzymatic actions and cause rapid sloughing of microvilli cells that line
                      the intestinal tract. This causes a malabsorption syndrome. The hosts immune status may help
                      determine the development of clinical disease. Immunosuppressed animals develop clinical signs of
                      Giardiasis much more commonly than normal animals. Remember stress is immunosuppressive.
                      Stress occurs in many forms and can be environmental, pregnancy, etc. Animals housed in groups
                      are more likely to develop Giardia infections.

                      Subclinical (no clinical signs) infections are common and infection may also be self-limiting in
                      27-35 days. Acute diarrhea that is occasionally watery is common. Chronic diarrhea may also
                      occur and appears as greasy semiformed stools, weight loss or poor weight gain. Vomiting or fever
                      are uncommon.

                      Standard fecal flotation procedures are inadequate and special fecal examination procedures are
                      required for identification of the parasites.

                      The treatment of choice is Metronidazole at a dose of 15-30 mg/kg of body weight orally given once
                      or twice daily. I have heard many reports recently of Panacur being used with success but I have
                      no personal experience with this method of treatment.

                      Resolution of clinical signs usually occurs within 7 days of treatment. Prevention involves boiling or
                      filtering of water before drinking and disinfection of contaminated premises with quaternary
                      ammonium compounds.