The cysts can stay infectious for up to three months in cold water.Many people with Giardia infections have no or few symptoms. They may, however, still spread the disease. Pathophysiology
The life cycle of Giardia consists of a cyst form and a trophozoite form. The cyst form is infectious and once it has found a host, transforms into the trophozoite form. This trophozoite attaches to the intestinal wall and replicates within the gut. As trophozoites continue along the gastrointestinal tract, they convert back to their cyst form which is then excreted with feces. Ingestion of only a few of these cysts is needed to generate infection in another host.Infection with Giardia results in decreased expression of brush border enzymes, morphological changes to the microvillus, increased intestinal permeability, and programmed cell death of small intestinal epithelial cells. Both trophozoites and cysts are contained within the gastrointestinal tract and do not invade beyond it.The attachment of trophozoites causes villous flattening and inhibition of enzymes that break down disaccharide sugars in the intestines. Ultimately, the community of microorganisms that lives in the intestine may overgrow and may be the cause of further symptoms, though this idea has not been fully investigated. The alteration of the villi leads to an inability of nutrient and water absorption from the intestine, resulting in diarrhea, one of the predominant symptoms. In the case of asymptomatic giardiasis, there can be malabsorption with or without histological changes to the small intestine.
Giardiasis is a parasitic disease caused by Giardia duodenalis (also known as G. lamblia and G. intestinalis). Infected individuals who experience symptoms (about 10% have no symptoms) may have diarrhea, abdominal pain, and weight loss. Less common symptoms include vomiting and blood in the stool. Symptoms usually begin 1 to 3 weeks after exposure and, without treatment, may last two to six weeks or longer.Giardiasis usually spreads when Giardia duodenalis cysts within feces contaminate food or water that is later consumed orally. The disease can also spread between people and through other animals. Cysts may survive for nearly three months in cold water. Giardiasis is diagnosed via stool tests.Prevention may be improved through proper hygiene practices. Asymptomatic cases often do not need treatment. When symptoms are present, treatment is typically provided with either tinidazole or metronidazole. Infection may cause a person to become lactose intolerant, so it is recommended to temporarily avoid lactose following an infection. Resistance to treatment may occur in some patients.Giardiasis occurs worldwide. It is one of the most common parasitic human diseases. Infection rates are as high as 7% in the developed world and 30% in the developing world. In 2013, there were approximately 280 million people worldwide with symptomatic cases of giardiasis. The World Health Organization classifies giardiasis as a neglected disease. It is popularly known as beaver fever in North America. Signs and symptoms
Symptoms vary from none to severe diarrhea with poor absorption of nutrients.