Giardiasis

 

Giardiasis.

Hill diarrhea, Beaver fever etc.

P.K. Ghatak, MD

Giardiasis consists of a number of gastrointestinal diseases caused by Giardia duodenalis. Giardia is a flagellated protozoan, present in the water of the lakes and small streams contaminated by human and certain animal feces.

Giardia exits in two forms - trophozoite and cyst forms. The cysts have a tough outer shell which protects and makes them survive a long time. The cysts are infective form, and humans are infected when they eat and drink contaminated food and water. The outer shell of the cysts dissolves in the small intestine and each cyst releases two giardia trophozoites The trophozoites live in the lumen of the intestine by attaching to the surface cells and also live in the crypts of intestinal villus processes. They extract food and nutrition from intestinal cells. Giardia multiply by binary fission.

The presence of giardia trophozoites inside the intestine provokes the body to react by activating CD4 cells and Interleukin-6 (IL-6) and other cytokines. The cytokines causes inflammation and giardia releases enzymes which breaks down proteins that binds surface cells of the intestine, This results in cell loss of enterocytes and destruction of villi. As a result of villus, atrophy and a reduction of the surface area of the small intestine occurs.

[Protozoa means “ The first animal “. It is a unicellular organism, having a central nucleus but lacks a well defined cell wall and organized mitochondria in the cytoplasm. Protozoa exhibits free movement and predation behavior and lives independent as a free agent and/or as a parasite.]

Diseases produced by Giardia.

A. Acute gastroenteritis. B. Chronic diarrhea. C. Malabsorption syndrome. D. Irritable bowl syndrome, lactose intolerance and other sequels.

Acute gastroenteritis.

Within 2 weeks following infection, patient develop acute explosive watery diarrhea of foul – fishy smelling stool, several times a day. The stool contains fakes of denuded intestinal epithelium and undigested fat, which floats on the surface. Campy abdominal pain is common, a low grade fever is seen in some cases. Weakness and debility follows. Diarrhea may last for weeks and can turn to a chronic condition.

Chronic diarrhea.

Without treatment, diarrhea in general does not subside. Frequency of liquid stool lessens. Nausea and anorexia develop.

Malabsorption syndrome.

Reduction in number and height of villi resembles changes seen in tropical sprue and gluten enteropathy. Loss of nutrients, vitamins and minerals results in general debility, loss of weight and patients become susceptible to frequent infections.

Sequels:

Intestinal bacterial overgrowth, specially the pathogenic group, results in increased IgA production. Immune reactions manifests as arthralgia, muscle pain and weakness, irritation and headaches. Some patients have aggravated immune disease like flair up of Cohn's disease.

Development of Irritable Bowl syndrome is thought to be an imbalanced growth of

beneficial / pathogenic bacterial colonies. Lactose intolerance is also common.

Diagnosis:

In acute diarrhea, the stool examination will detect Giardia trophozoites and few cysts. In chronic diarrhea in giardia trophozoites have time to change into cysts. Consequently, diagnosis depends on recognition of cysts in the stool. Fluorescence antibody testing increases detection of giardia.

In malabsorption, endoscopic small intestinal biopsy detects typical atrophic intestinal villi. Lymphocyte infiltration of crypts and giardia trophozoites.

Treatment:

In any stage of infection, Metronidazole and analogs of Metronidazole used to be very effective. But overuse and misuse resulted in drug resistance. In such cases, some are using Albendazole. The WHO recommends Quinacrine and related synthetic quinine tablets.

In pregnant women, Paromomycin is used. FDA recommends Nitozoxanid for children.

Prevention:

Because sheep, cattle, mask rates. beavers, dogs and other rodents are infected by giardia, it is difficult if not impossible to protects lakes and small streams that flow down the hills into the valley. Chlorination of water do not kill the cysts of giardia. Boiling water and microwave radiation will destroy giardia cysts. Basically, it is the task of Public health officials to educate people about waterborne diseases and how to protect themselves.

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