Giardia

Recently, we discussed the topic of infection with parasitic worms. While some of these can reach impressive lengths (like a 55-foot tapeworm), most parasites that trouble humans are microscopic in nature. The most common of these in the U.S. is giardia. Over a million Americans are affected annually.

An infection with giardia is called “giardiasis.” The parasite lives all over the world in bodies of water. If ingested during a stage of its life cycle called a “cyst,” The Giardia cyst is a dormant stage that survives until it finds a host. It, then, colonizes the small intestine and, for lack of a better word, “hatches.” Giardia then feeds off the host’s dietary nutrients. Once it reproduces, the parasite reverts back to the cyst stage and exits in bowel movements.

Note: Giardia has also been known as giardia lambia, giardia intestinalis, and giardia duodenalis. They are essentially the same microbe.

Giardia especially thrives in poorly developed regions where public sanitation is questionable. It spreads easily from host to host, with children infected more often than adults; although it prefers bodies of water, childcare centers are a possible source of outbreaks in the U.S.

SYMPTOMS OF GIARDIASIS

Giardiasis can cause a variety of intestinal symptoms which can range from mild to severe. In about half the cases, there are no symptoms at all. If a person becomes ill, symptoms will occur in one or two weeks after infection. This is the time it takes the giardia cyst to “hatch.” Once that happens, common symptoms include:

Watery diarrhea.
Greasy-appearing bowel movements that float.
Abdominal pain, gas, and bloating.
Nausea and vomiting.
Loss of appetite.
Worsening fatigue
Weight loss
Dehydration

Less commonly, sufferers complain of itchiness, hives, swelling in the joints and around the eyes. Most people have symptoms for two to six weeks. Some people have longer-lasting symptoms. Fortunately, the infection usually resolves itself after a few weeks, but some people continue to have symptoms for weeks or months.

TRANSMISSION OF GIARDIA

Animals and humans can get giardiasis, passing it on to others through their excrement. Other common ways for giardia to enter a host include:

Eating or drinking contaminated food or unfiltered water.
Contact with contaminated surfaces.
Travel to regions with poor sanitation.
Swimming in contaminated water.
Contact with babies and toddlers or their diapers.
Having anal sex with an infected person.

COMPLICATIONS OF GIARDIASIS

Possible complications include:

Dehydration. Dehydration is the primary risk from giardiasis, as the nausea, vomiting, and diarrhea can cause a large amount of fluid loss.

GI problems. If giardiasis lasts a long time, it can damage the lining of your small intestine, which can damage its ability to absorb nutrients.

Autoimmune disease. In some people with severe chronic giardiasis, part of your immune response to the infection becomes hyperactive, continuing even after the infection is gone.

DIAGNOSIS OF GIARDIASIS

Giardiasis is diagnosed with certainty by identifying the organism in stool samples under the microscope. Most of the time, however, the specific set of symptoms mentioned earlier are the main clue that triggers treatment.

TREATMENT OF GIARDIASIS

There are various anti-parasitic drugs that are commonly used to treat significant illness caused by giardia. With treatment using the antibiotics below, you can expect recovery in about a week:

Metronidazole (Flagyl®).
Tinidazole (Tindamax®).
Nitazoxanide (Alinia®).
Paromomycin (Humatin®).

Of the above, metronidazole is the most commonly used but may cause complications during pregnancy. Until recently, it was available without prescription as a “fish antibiotic.”

PREVENTING INFECTION WITH GIARDIA

As giardia can live even in the clearest creek water in the backcountry, it might be hard to avoid off the grid. However, there are strategies that help prevent problems:

Wash hands frequently, especially before eating or having sex and after using the bathroom or contact with soil or animals.
If someone in your group has been sick, clean and disinfect everything they’ve touched, including work surfaces and bedding.
Wash fruit and vegetables in clean water before eating.
Avoid raw foods and unbottled water when traveling abroad.
Be wary when swimming in natural ponds, streams, and lakes. Even municipal swimming pools are risky if not well-maintained. Try not to swallow water in these areas.

Although animals can spread Giardia to people, you are unlikely to get a Giardia infection from dogs or cats. The type of Giardia that makes people sick is usually not the same type that affects pets.

JOE ALTON MD

Dr. Joe Alton