Giardiasis

What is giardiasis?

Giardiasis is an intestinal infection caused by a microscopic parasite called Giardia. This parasite lives all over the worldespecially in bodies of water. If you accidentally swallow itit takes up residence in your small intestine and multipliesfeeding off the nutrients there. This can cause a variety of intestinal symptomsincluding foul-smelling diarrheabloating and gasstomach crampsnausea and fatigue.

Giardiasis symptoms can be mild to severeand some people never have symptoms. The infection typically clears by itself after a few weeksbut people with weaker immune systems may have a harder time clearing it. A healthcare provider can prescribe antiparasitic medications for giardiasis if you need them. Sometimespeople continue to have symptoms for weeks to months after the infection has gone.

How common is giardiasis?

Giardiasis is common throughout the world. It’s the most common parasite infection in the U.S.where it affects over a million people each year. In developed countries in generalit affects an estimated 10% of the population. In developing countriesgiardiasis affects an estimated one-third of the population.

Giardia thrives in regions and environments with less public sanitationespecially in natural bodies of water and inadequately sanitized public water supplies. Children are more often infected than adultsespecially those under the age of 4. In the U.S.childcare centers are a frequent source of outbreaks.

What are the symptoms of giardiasis?

About half of people never develop symptoms of giardiasis. Among those who docommon symptoms include:

• Watery diarrhea.
• Fatty or greasy poop that floats.
• Stomach pain and cramping.
• Intestinal gas and bloating.
• Nausea and loss of appetite.
• Increasing fatigue.

Less common symptoms can include:

• Itchy skin.
• Hives.
• Swelling around your eyes.
• Swollen joints.

Long-term effects

Most people have short-term symptoms during their infectionbut occasionallysome people have longer-lasting or recurring symptoms. They might develop dehydration and weight loss from the chronic diarrhea and nausea. Sometimesthey develop lasting digestive difficultieslike lactose intolerance.

What causes giardiasis?

Giardia infection happens when you accidentally ingest the microscopic parasite during the cyst stage of its life cycle. The Giardia cyst is sort of like an egg that can survive in the wild until it finds a body (host) to hatch in. After you swallow itthe cyst settles and “hatches” in your small intestine. The parasite feeds off your nutrients and multiplies. After thisit changes back into a cyst and passes out in your poop.

How is giardiasis transmitted to humans?

Animals and humans both get giardiasisand they can both pass it on to others through their poop. The Giardia cyst lives within microscopic traces of poop within your environment that are too small to see. These traces can linger on surfacesin bodies of water and on people’s hands if they don’t wash them well enough after using the bathroom. They can also transfer to people’s food and drinking water.

Some common ways you might get giardiasis include:

• Drinking or swimming in untreated or unfiltered water.
• Traveling abroadespecially in developing countries.
• Interacting with groups of babies and toddlers who wear diapers.
• Eating or drinking contaminated food or water.
• Touching a surface that an infected person touched.
• Having anal sex with an infected person.

How long does giardiasis take to kick inand how long does it last?

The incubation period for giardiasis is one to two weeks from infection. That’s how long it takes for the Giardia cyst to release the parasite and for the parasite to begin to multiplyalerting your immune system. When your immune system activates to remove itthat’s when you might begin to notice symptoms. Symptoms typically last between two and six weeksbut in some peoplethey can last longer.

What does giardiasis do to you?

Giardia infection doesn’t always cause noticeable symptomsbut it can. Some symptoms are due to the parasite itselfand others are due to your body activating to remove the parasite. For examplethe parasite feeding off your nutrients might sap your energymaking you feel increasingly tired. Diarrheaswelling and skin reactions are symptoms of inflammationpart of your immune system’s response.

These symptoms are short-lived for most people. They go away when the infection does. But if giardiasis lasts a long timeor keeps coming backit can do more long-term damage. This might happen if you have a weaker immune systempossibly from a preexisting health condition. In developing countriesmalnutrition and lower health status can make people more vulnerable to complications from giardiasis.

What are the possible complications of giardiasis?

Possible complications include:

• Dehydration. Dehydration is the primary short-term risk from giardiasisand it can also happen gradually over the long term. Anyone who’s having diarrhea and/or vomiting loses a lot of fluids. It can be hard to replace the fluids as fast as you’re losing them. Children and people over age 65 are especially vulnerable to dehydrationso it’s important for caretakers to stay alert.
• Gastrointestinal disease. If giardiasis lasts a long timeit can damage the lining of your small intestine. This can cause chronic gastrointestinal symptoms and trigger irritable bowel syndrome. It can also damage your intestine’s ability to absorb the nutrients in your food. You could develop nutritional deficiencies. This could affect growth and development in children.
• Autoimmune disease. In some people with severe and/or chronic giardiasislong-term inflammation triggers an autoimmune response. This means that part of your immune response to the infection becomes hyperactive and automaticcontinuing even after the infection is gone. Some people have developed reactive arthritis, chronic fatigue syndrome or new food allergies.

How is giardiasis diagnosed?

A healthcare provider can diagnose giardiasis by testing a sample of your poop for evidence of Giardia. This might take a few tries because you might pass the cysts in your poop one day but not the next. It’s not always necessary to identify giardiasis this waythough. Healthcare providers often prescribe medications to treat giardiasis based on your symptoms alonewithout needing to diagnose it first.

What medications or other treatments do healthcare providers prescribe for giardiasis?

Not everyone will need treatment for giardiasis. But if you have symptomsyour healthcare provider can prescribe antiparasitic medications to make the infection go away faster. With medicationsmost people feel better within a week. But underlying medical conditions can affect your response. If your condition is more severeyou might need additional supportlike rehydration or antidiarrheal medications.

Medications

Antibiotics for giardiasis include:

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

Different medications affect different people in different ways. If your first prescription doesn’t work or causes intolerable side effectsyour provider will offer an alternative. Your provider might recommend that everyone in your household take them to prevent the infection from spreading. If you’re pregnantthey might recommend delaying treatment because these drugs could potentially be toxic to the fetus.

Can Giardia go away on its own?

Yesgiardiasis often goes away on its ownand if your symptoms are mildyour provider might encourage you to let it do that. When populations use certain antibiotics against common infections too oftenthe infections can begin to become resistant to those antibiotics. This is starting to occur in certain places with giardiasis. If you can go without medicationyou can help prevent antibiotic resistance.

But giardiasis doesn’t always go away in everyone. And in some peopleit can be very persistent. If you continue to have symptoms for longer than six weeksvisit your healthcare provider. They can test you to find out if you’re still infectedor if your symptoms are due to the after-effects of the infection. They can offer treatment for either the infection itself or your symptoms and screen you for complications.

What happens if Giardia is left untreated?

Untreated Giardia infection often goes away by itself. But if it doesn’tit can cause long-term complications for your digestive systemand even your immune system. It’s important to see a healthcare provider if you have symptoms lasting longer than six weeks. If your provider prescribes antibioticsit’s important to take the full course to make sure the infection doesn’t rebound.

What happens if the treatment doesn’t work?

If you’ve taken antibiotics but testing later finds you’re still infectedit’s possible that:

• You didn’t take the full course or you need a stronger dose.
• You’ve been reinfected through your environment.
• You need a different medication or combination.
• You have a weakened immune system for some reason.

Your healthcare provider will investigate these possibilities. If you have an immune deficiencyyou might need separate treatment for that. If necessaryyour provider will consult an infectious disease specialist to devise an individualized treatment plan for you that combines different types of medications.

What can I expect if I get giardiasis?

About half of people who get giardiasis never have symptoms. For those who dothey’re usually mild and temporary. If your symptoms are noticeableyour healthcare provider can prescribe medications. With treatmentmost people feel better within a week. Without treatmentit might take two to six weeks.

Some people sometimes have a harder time with giardiasis. They might have more severe symptoms or might need extra help clearing the infection. If the parasite significantly damages your small intestineyou might continue to have gastrointestinal symptoms for a long timeeven after the infection has gone away.

How can I lower my risk of getting or spreading giardiasis?

It’s hard to avoid something in your environment that’s too small to see. But there are steps that individuals and communities can take to prevent infection and reduce transmission of Giardia to others. For example:

• Personal hygiene: Practice frequent hand washing to prevent germs from spreadingespecially before eating or having sex and after using the bathroom or interacting with soil or animals.
• Household hygiene: Clean and disinfect the bathrooms in your home regularly. If someone in your household has been sickclean and disinfect everything they’ve touchedincluding linens.
• Safe food practices: Wash fruit and vegetables in clean water before eating. Avoid raw foods and unbottled water when traveling abroadwhere the local water might be contaminated.
• Safe water use: Be wary when swimming in natural pondsstreamslakes and swimming holesand even public swimming pools if they don’t have a filtering system. Chlorine and iodine treatments aren’t always enough to kill Giardia. Try not to get any water in your mouth.

When should I see a healthcare provider about giardiasis?

Contact a healthcare provider if:

• Your symptoms aren’t improving fast enough and you’d like treatment.
• You or someone in your care has signs of dehydration.
• Your medications cause intolerable side effects.
• Your symptoms haven’t improved after taking medications.