Transmission of giardiasis has also been documented in male homosexuals. Pets may also harbor Giardia. A person becomes infected with Giardia by swallowing cysts of the parasite. This can occur when an individual eats or drinks food or water contaminated with Giardia cysts, or through direct contact with an individual infected with Giardia who has poor personal hygiene. The most common symptoms of Giardiasis include diarrhea, abdominal cramps, pale and greasy stools, fatigue, bloating, and weight loss.
Fever is usually absent.
Many persons with Giardia have no symptoms at all. Symptoms may begin 3 to 25 days after swallowing Giardia cysts, but usually within 10 days. Giardiasis is typically diagnosed by finding Giardia lamblia cysts in a stool sample submitted to a laboratory. Since cysts are intermittently passed in the stool, more than one specimen may be necessary to make the diagnosis because the cysts may not be in every stool specimen. Some individuals recover from giardiasis without any treatment.