Infection with the protozoan parasite Giardia; Giardia lamblia may cause diarrhea, dyspepsia, and occasionally malabsorption in humans. Syn: lambliasis.
Alternative Names: Giardia; Traveler's diarrhea - giardiasis.
Giardiasis, an illness that affects the digestive tract, is caused by a microscopic parasite called Giardia lamblia. The parasite attaches itself to the lining of the small intestines in humans, where it sabotages the body's absorption of fats and carbohydrates from digested foods.
Giardia is one of the chief causes of diarrhea in the United States, and is transmitted through contaminated water. It can survive the normal amounts of chlorine used to purify community water supplies, and can live for more than 2 months in cold water. As few as 10 of the microscopic parasites in a glass of water can cause a severe case of giardiasis in a human being who drinks it.
Young kids are three times more likely to have giardiasis than adults, which leads some experts to believe that our bodies gradually develop some form of immunity to the parasite as we grow older. But it isn't unusual for an entire family to have giardiasis, with some family members having diarrhea, some just crampy abdominal pains, and others with few or no symptoms.
It's estimated that between 1% and 20% of the U.S. population has giardiasis, and this figure may be 20% or higher in developing countries, where giardiasis is a major cause of epidemic childhood diarrhea. But more than two thirds of people who are infected may have no signs or symptoms of illness, even though the parasite is living in their intestines.
People and animals (mainly dogs and beavers) who have giardiasis can pass the parasite in their stool. The stool can then contaminate public water supplies, community swimming pools, and "natural" water sources like mountain streams. Uncooked foods that have been rinsed in contaminated water may also spread the infection.
In child-care centers or any facility caring for a group of people, giardiasis can easily pass from person to person. At home, an infected family dog with diarrhea may pass the parasite to human family members who take care of the sick animal.
The incubation period for giardiasis is 1 to 3 weeks after exposure to the parasite. In most cases, treatment with 5 to 7 days of antiparasitic medication will help kids recover within a week's time. Medication also shortens the time that they're contagious. If giardiasis isn't treated, symptoms can last up to 6 weeks or longer.
The most common symptoms of giardia include:
Diarrhea, usually lasting 7 to 10 days. It can last longer but can also get better within 2 to 4 days. There first may be a large amount of watery diarrhea followed later by greasy, foul-smelling stools that may float. This is a sign that fat is not being digested properly and instead is being passed from the body in the stool.
- Abdominal cramps or tenderness.
- Nausea and loss of appetite.
- Passing more gas or having more bloating than usual.
Symptoms of chronic giardiasis include:
Loose, soft, greasy stools (not always watery or liquid). Sometimes the stools may be foul-smelling or foamy and are often passed in small amounts.
Causes and Risk factors:
- Discomfort in the abdomen or pit of the stomach that is often worse after a meal.
- Belly cramps, bloating, or pain.
- Passing more gas than usual.
- Persistent bad breath or belching that sometimes smells of sulfur.
- Occasional headaches.
- Weight loss.
- General feeling of discomfort or illness (malaise), weakness, or fatigue.
Giardia is caused by the parasite Giardia intestinalis (also called Giardia lamblia).You're likely to pick up the parasites in one of three ways:
Giardia cysts are spread via the fecal-oral route. Cysts may be ingested with contaminated food or water, or acquired from unwashed hands.
IN WATER: This is the main source of giardia infection. The parasites are found in lakes, ponds, rivers and streams worldwide, as well as in municipal water supplies, wells, cisterns, swimming pools, water parks and spas. Giardia parasites have even turned up in touch tanks in aquariums and museums. Ground and surface water can become contaminated from agricultural runoff and wastewater discharge. Because giardiasis affects beavers, muskrats, small rodents and a variety of birds, reptiles and fish, water can also become contaminated from animal feces. Children in diapers and people with diarrhea may accidentally contaminate pools and spas. You can become infected if you drink from streams or lakes that contain the parasites, drink contaminated tap water at home or abroad, or accidentally swallow water from a tainted pool or spa.
IN FOOD: Giardia parasites can be transmitted through food — either because food handlers with giardiasis don't wash their hands or because raw produce is irrigated or washed with contaminated water. Because cooking food kills giardia, food is a less common source of infection than water is, especially in industrialized countries. However, outbreaks can occur through ice and infected food service workers.
BY DIRECT CONTACT: You can get giardiasis if your hands become contaminated with fecal matter — parents changing a child's diapers are especially at risk. So are child care workers and children in child care centers. The giardia parasite can also spread through anal sex.
Anyone can get giardiasis, but some persons are at increased risk:
- Diaper-aged children who attend day-care centers.
- Persons who travel to countries where the water and food may be contaminated with Giardia.
- Hikers, campers, and others who drink unfiltered and untreated water from contaminated sources.
- Several community-wide outbreaks of giardiasis have been linked to drinking municipal water contaminated with Giardia.
Giardia infection is almost never fatal in industrialized countries, but it can cause lingering symptoms and serious complications, especially in infants and children under 5. The most common complications include:
Dehydration: Often a result of severe diarrhea, dehydration occurs when the body doesn't have enough water to carry out its normal functions.
- Failure to thrive: Chronic diarrhea from giardia infection can lead to malnutrition and harm children's physical and mental development.
- Lactose intolerance: Many people with giardia infection develop lactose intolerance — the inability to properly digest milk sugar. The problem may persist long after the infection has cleared, leading to malabsorption and weight loss in some.
- Skin rash: In rare cases, giardia infection may cause a skin rash or hives.
Diagnosis of giardiasis is usually based on:
Medical history and physical exam: If your history and physical exam strongly suggest the symptoms are due to giardiasis, some doctors may prescribe a single course of treatment before doing further tests.
- Stool analysis (also known as ova and parasite test).
- Antigen tests that detect proteins (antigens) from the Giardia parasite.
- String test, which may be used if the stool analysis is inconclusive. The string test collects a sample of the contents of the small intestine so it can be examined for the presence of parasites. This test is rarely done.
Fluid from the upper part of the small intestine (duodenal fluid) may also be examined under a microscope to look for the parasite or to do an antigen test. A duodenal fluid sample is collected by endoscopy.
Other tests to help detect giardiasis or similar conditions may sometimes be done if you are experiencing long-term symptoms, especially if problems with malabsorption are occurring. These tests are used to examine the small intestine (upper GI series) or to collect a sample (biopsy) of the upper small intestine to identify what is causing the infection.
Two therapies are approved by the FDA for the treatment of giardiasis:
Metronidazole is not indicated for use in giardiasis but is the drug most often used in the United States. Metronidazole and tinidazole belong to a class of drugs called the nitroimidazoles. Metronidazole is a first generation nitroimidazole, and tinidazole is a second generation nitroimidazole.
According to the 2007 Medical Letter, metronidazole is administered in doses of 250 mg 3 times a day for 5-7 days for adults, and 15 mg/kg 3 times a day for 5-7 days in children.1 Side effects associated with metronidazole include metallic taste, dark urine, and gastrointestinal symptoms. As previously mentioned, metronidazole is not approved by the FDA for the treatment of giardiasis.
Tinidazole is indicated for the treatment of giardiasis in adults with a single 2 g dose and with 50 mg/kg single dose in children over 3 years of age. In eight randomized comparative studies totalling 299 adult and pediatric patients, the average cure rate for tinidazole in giardiasis was 90%.2-8. Tinidazole has also demonstrated activity against the cyst stage of giardiasis in clinical use.
Nitazoxanide is indicated for giardiasis in adults with 500 mg every 12 hours with food for 3 days, and in children with 100-200 mg every 12 hours with food for 3 days. Nitazoxanide resolved the symptoms of giardiasis in 85% of 110. Peruvian children in one study Nitazoxanide has been shown to be more active in vitro against Giardia than metronidazole, and it is active against metronidazole-resistant Giardia
Medicine and medications:
Antibiotic therapy is standard in the treatment of giardiasis.
The following drugs and medications are in some way related to, or used in the treatment. This service should be used as a supplement to, and NOT a substitute for, the expertise, skill, knowledge and judgment of healthcare practitioners.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
- Albendazole (Albenza).
- Furazolidone (Furoxone).
- Nitazoxanide (Alinia).
- Tinidazole (Tindamax).