Giardia lamblia (PCR)

One of the most common intestinal infections caused by single-celled organisms worldwide. Giardia damages the brush border → lactase deficiency, fatty stools, sometimes chronic diarrhoea. PCR is considerably more sensitive than microscopic stool examination.

How Giardia lamblia lives in the small intestine

Giardia lamblia, also called Giardia duodenalis or intestinalis, is a flagellate. Its cysts survive for weeks in cold water, and just a few are enough for an infection. The trophozoites hatch from them in the duodenum. They do not penetrate the tissue but attach themselves to the surface of the small intestinal cells with an adhesive disc on their underside and multiply by binary fission. Further down the gut, under the influence of bile, they form cysts again, which are excreted in the stool. Many infections cause no complaints.

How Giardia affects the gut lining and the immune system

The suction and the enzymes released by Giardia shorten the microvilli, loosen the junctions between gut cells and cause more gut cells to die. With the reduced surface, the digestive enzymes located there, such as lactase, also decline; undigested milk sugar reaches the large intestine and is fermented there. At the same time, Giardia alters the bile acids needed for fat digestion, and the gut cells release more chloride and water. Defence relies mainly on secretory IgA and T cells. Giardia, however, can swap its surface proteins and so evade the antibodies – one reason for prolonged courses.

What happens when Giardia multiplies heavily?

If heavy colonisation persists for longer, nutrients are absorbed less well over the long term. In studies, deficiencies of fat-soluble vitamins, vitamin B12, iron and zinc were observed; in children in regions with frequent infections, delayed growth as well. After a large waterborne outbreak in Bergen, Norway, follow-up studies over several years found more irritable bowel complaints and persistent exhaustion among those affected than among comparison groups, even though the pathogen was no longer detectable. Persistent low-grade inflammation, an altered gut flora and heightened gut sensitivity are being investigated as explanations.

The interpretation is given in your report.