Parasitic Diarrhea (Giardiasis) in Dogs

Giardiasis is an intestinal infection caused by a parasitic protozoan (single celled organism) called Giardia lamblia. These protozoans are found in the intestines of many animals, including dogs and humans. This microscopic parasite clings to the surface of the intestine, or floats free in the mucous lining the intestine.

Sometimes known as "beaver fever", the disease is caused by infection with these little protozoans (giardia) that live in the gastrointestinal (GI) tract of the animals.  

Giardia occur in two forms: a motile feeding stage that lives in the intestine, and a non-motile cyst stage that passes in the feces. Encystment occurs as the parasite travels to the large intestine. The cysts are fairly resistant and can survive for several months as long as sufficient moisture is provided. Mature cysts are usually found in the feces of infected animals.

Animals become infected by ingesting cysts. These cysts break open in the intestine to release the motile feeding stage (trophozoite). Giardia increase their numbers by each organism dividing in half repeatedly by a process called binary fission.

Symptoms can be sudden, (acute), temporary (transient), non-continous (intermittent) or ongoing (chronic) and are more obvious in younger dogs than older ones. 

The signs of infection begin about one week post-infection and range from none in asymptomatic carriers, to mild recurring diarrhea consisting of soft, light-colored stools, to acute explosive diarrhea in severe cases. Other signs associated with giardiasis are weight loss, listlessness, fatigue, mucus in the stool, and anorexia.  

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