Giardia: Intestinal Infection, Symptoms and Treatment

Giardia is a micro-organism that causes a disease called giardiasis in humans. Giardiasis is one of several diseases that might be lumped together under the term gastroenteritis.

Giardia causes a form of gastroenteritis. Chronic cases are much more common and are characterized by brief periods of diarrhea with occasional constipation between attacks. It is normally accompanied by wind of an unpleasant odor, and many include gastric cramps, nausea, weight loss and fatigue.

There is also a general feeling of not being well. In more acute cases the symptoms may include nausea, vomiting, chills, headache, belching and general weakness. In acute cases it can be quite debilitating and require medical attention.

The disease is caused by a protozoan organism, Giardia intestinalis (also known as Giardia lamblia, or Giardia duodenalis). It would take about 1000 of the oval-shaped organisms to cover a distance of a centimeter if they were laid end to end.

Giardia has two stages to its life cycle. Outside the body it is spread in the form of a cyst that has a tough wall to protect it. Once swallowed it passes safely through the acid stomach, and after it enters the alkaline intestine, it changes into its trophozoite phase.

This form can move around in the small intestine by the beating of hair like projections from the cell. It can also attach to the gut wall, and appears to feed on the gut wall rather than from the food passing by in the intestine.

It causes irritation to the small intestine which causes the symptoms. When the infection is severe this irritation creates problems with the absorption of food across the small intestine wall. In young children this interference can lead to weight loss and general illness.

The organism forms cysts again as it moves out of the body in the feces. Some trophozoites may escape with feces but they don’t live long, and do not reinfect people since they cannot survive in the acid stomach.

Many people carry this parasite in their gut and do not show any symptoms. Various studies have suggested that between 5 and 25 percent of the population carry Giardia, and excrete cysts, although they do not show the symptoms. It also appears the parasite can live in cats, dogs, horses, sheep and cattle, and these may well be a source of infection.

About one-third of the diagnoses are done on small children (toddlers between 1 and 7). The next biggest group are women in the 20- to 30-year age group. This strongly suggests a disease transmitted among toddlers at preschools by the fecal-oral route. Their mothers dealing with diapers also have a good chance of getting infected. The cysts are very infective.

This disease is prevalent in conditions where poor hygiene is common. Young children and people living with inadequate water supply are at risk. In a study, 46 percent of toddlers (1 to 2 years old) carried the parasite, and 21 percent of toddlers (2 to 3 years old).

The studies all point to personal hygiene as the way to stop the spread of this parasite. Washing hands after using the toilet is the key to this disease, like many other causes of diarrhea. Treatment of Giardia infection (giardiasis) is a one day course of antibiotics and the sufferer is usually better within a week or 10 days.

NOTE: It is important to discuss treatment options with a healthcare provider.

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