Giardia are tiny, one-celled protozoal parasites found in the gastrointestinal tract of most domestic and wild mammals, including people. They also infect domestic and wild birds. Giardiasis, sometimes called “beaver fever”, is the disease caused by an infection from these parasites. Giardia are found throughout the United States and in many other parts of the world. Infection with Giardia is common, but disease from them is not. Some dogs carry Giardia in their gastrointestinal tracts without showing any clinical signs of discomfort. This is called a “latent” or subclinical infection. However, very young puppies, and dogs with compromised immune systems, can have severe reactions to these parasites, including loss of appetite, malnutrition, diarrhea, weight loss, tiredness, weakness, bloody or pale-colored, greasy, strong-smelling stools and even death. Giardia also pose a risk to human health, especially in immunocompromised people such as the elderly, newborns, pregnant women and people suffering from cancer, AIDS or other serious diseases.
Giardia are found world-wide. They have what is known as a direct life cycle. Dogs become infected when they ingest the cyst (interchangeably called the “oocyst”) form of this parasite by drinking contaminated water, eating contaminated food, licking contaminated fur or otherwise coming into contact with contaminated feces in the environment. The cysts lodge in the upper part of the dog’s small intestine, called the duodenum. There, each cyst produces several motile larvae, known as
Many dogs infected with Giardia have a latent or subclinical infection, which means that they really don’t show any noticeable symptoms of illness. However, the parasites eventually damage the lining of the intestines of the animals that they infect, disrupting digestion and using up nutrients that the animals need for normal health. The effects of Giardia are most pronounced in young dogs, old dogs and those with impaired immune systems. The profuse diarrhea that frequently
The disease caused by infection with Giardia is not difficult for veterinarians to diagnose. Examination of a dog’s feces can reveal the trophozoite and/or cyst forms of the organism. Giardia can also be identified through more advanced, specialized tests. Most veterinarians evaluating a dog with diarrhea, abdominal pain and other signs of gastrointestinal upset will take a blood sample and perform a complete blood count and a serum biochemistry panel. They will also probably take
Giardia is treatable, usually on an outpatient basis. Unfortunately, the effectiveness of treatment is evaluated based on the presence or absence of cysts in the affected dog’s feces, which does not necessarily equate with whether the parasites are present inside of the dog. A dog can remain internally infected, without shedding the cyst form of the organism at the time the fecal sample is taken. In addition, infection can recur after the parasite is initially