Giardiasis is a diarrheal disease caused by the microscopic parasite Giardia duodenalis (or “Giardia” for short). Once a person or animal has been infected with Giardia, the parasite lives in the intestines and is passed in stool (poop).

Protozoa

The flagellate protozoan Giardia intestinalis (previously known as G lamblia or G duodenalis), its causative agent, is the most commonly identified intestinal parasite in the United States [1, 2] and the most common protozoal intestinal parasite isolated worldwide. Infection is more common in children than in adults.

The best single test for diagnosing giardiasis is antigen testing of the stool. For antigen testing, a small sample of stool is tested for the presence of Giardial proteins. The antigen test will identify more than 90% of people infected with Giardia.

For those who do get sick, signs and symptoms usually appear one to three weeks after exposure and may include: Watery, sometimes foul-smelling diarrhea that may alternate with soft, greasy stools.

Giardiasis treatment Mild infections can go away on their own in a few weeks. If symptoms are severe or aren’t going away, medicine can be used. Infected people who work at a daycare or nursing home may also be treated with medicine. This can help prevent the illness from spreading.

Complications. Without treatment, giardia can become chronic, but this is rare. It can last for years, with repeated bouts of diarrhea, vitamin deficiencies, and tiredness. A person who recovers without treatment may continue to have and to shed the parasite, although this does not always happen.

lamblia causes giardiasis. N. fowleri is a water-borne amoeba that enters the brain through the nasal passage, causing a type of brain damage known as primary amoebic meningoencephalitis (PAM).