Giardia lamblia is a flagellate protozoan parasite that can be found in the intestinal tract of humans and most domestic animals. Giardia can cause protracted intermittent diarrhea in some individuals but can exist as a latent infection  (present but not causiong symptoms) in others.

Giardia can affect humans and most domestic animals. Younger animals may be more susceptible. Immunodeficient adults, young animals and animals confined in large groups are at increased risk. Giardia does not appear to be highly host specific; spread of infection from dogs and cats to people should be considered possible. Most infections produce no clinical signs. But if diarrhea results, it can be acute and short lived, intermittent or chronic. Fatty stools or weight loss may be observed. Vomiting, fever and anorexia may occur but are not typical. Signs consistent with either acute or chronic large bowel diarrhea occur in cats. A physical exam may show no significant abnormalities.

The giardia life cycle is direct. Cysts are ingested and excyst in the duodenum, each cyst producing two motile trophozites that replicate within the wall of the small intestine. Before being shed in feces, the trophozite encysts. On excretion, the cysts are infective to another host. Cysts can survive for days to weeks in a cool, moist environment. Trophozoites are thought to cause sloughing of intestinal epithelial cells, resulting in blunting of the intestinal villi and subsequent reduction in absorptive surface area causing malabsorption and diarrhea. Abnormalities in the immune system likely predispose individuals to clinical infection. Immunosuppressive drugs may predispose to clinical infection.

Giardia vaccination has not been shown to be an effective treatment of an infected individual. We use the vaccine to reduce the shedding of cysts, which in turn reduces the probability of contamination and passing it to other animals or people.. Many individuals may be cured with prompt diagnosis and appropriate treatment, but recurrent infections are well documented.  The most effective treatment at this time is the use of fenbendozole (Panacur) on a daily basis for 5-6 days in a row. It has recently been stated in the literature that the concurrent use of a probiotic, (Gastromate, Probiosin) may improve the effectiveness of the Fenbendozole treatment. It is also recommended to bath the affected animals to eleminate any cysts that are attached to the hair coat. Thoroughly drying any areas, like outside runs, where the animals are kept would also be beneficial.