Additionally, peristalsis and the renewal of enterocytes provide further protection against parasites. Nitric oxide production
Nitric oxide does not kill the parasite, but it inhibits the growth of trophozoites as well as excystation and encystation. Innate immune system
Lectin pathway of complement
The lectin pathway of complement is activated by mannose-binding lectin (MBL) which binds to N-acetylglucosamine. N-acetylglucosamine is a ligand for MBL and is present on the surface of Giardia. The classical pathway of complement
The classical pathway of complement is activated by antibodies specific against Giardia. Adaptive immune system
Antibodies
Antibodies inhibit parasite replication and also induce parasite death via the classical pathway of complement.Infection with Giardia typically results in a strong antibody response against the parasite. While IgG is made in significant amounts, IgA is believed to be more important in parasite control. IgA is the most abundant isotype in intestinal secretions, and it is also the dominant isotype in mothers milk. Antibodies in mothers milk protect children against giardiasis (passive immunization). T cells
The major aspect of adaptive immune responses is the T cell response. Giardia is an extracellular pathogen. Therefore CD4+ helper T cells are primarily responsible for this protective effect.One role of helper T cells is to promote antibody production and isotype switching. Other roles include cytokine production (Il-4,IL-9) to help recruit other effector cells of the immune response. Diagnosis
According to the CDC, detection of antigens on the surface of organisms in stool specimens is the current test of choice for diagnosis of giardiasis and provides increased sensitivity over more common microscopy techniques.
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.