Gastroenteritis Giardiasis

Overview

Giardiasis (say: gee-ar-DYE-uh-sis) is an infection of the small intestine caused by a tiny parasite called Giardia. It is a common cause of gastroenteritis — inflammation of the stomach and intestines that leads to diarrhea, cramps, and feeling sick. Giardia can spread through water, food, hands, surfaces, and close contact with someone who is infected.

Giardiasis is one of the more common parasitic causes of diarrhea worldwide. It is more common in places with limited clean water and sanitation, but cases happen everywhere.

Anyone can get giardiasis. It is seen more often in young children, people in childcare settings, travelers, hikers and campers, people who drink untreated water, and people with a weakened immune system (the body's germ-fighting system).

Symptoms

Common symptoms

• Watery diarrhea that may come and go
• Greasy, floating, or bad-smelling stools
• Gas and bloating
• Stomach cramps
• Feeling sick (nausea) or vomiting
• Tiredness
• Weight loss
• Dry mouth, dark urine, or dizziness from dehydration (losing too much water)

Symptoms in children

• Diarrhea, sometimes with poor appetite
• Irritability or unusual sleepiness
• Fewer wet diapers or less urine than usual
• Belly pain
• Slow weight gain
• Vomiting

Symptoms in older adults

• Dehydration can come on faster
• Weakness or dizziness
• Confusion or new drowsiness if dehydration is severe
• Worsening of heart, kidney, or other long-term conditions

Causes

Main causes

• Swallowing Giardia cysts — tiny, tough forms of the parasite that can survive in water and on surfaces.
• Drinking water or eating food that is contaminated with the parasite.
• Putting hands, toys, or objects in the mouth after touching contaminated surfaces or stool.
• Close contact with an infected person, such as in a household or childcare setting.
• Contact with infected animals or their stool.

Risk factors

• Drinking untreated water from lakes, streams, wells, or taps in areas with poor sanitation
• Swimming or swallowing water in pools, lakes, rivers, or streams
• Close contact with someone who has giardiasis, especially in childcare or a household
• Handling infected animals or cleaning up their stool
• Sexual contact that may bring stool near the mouth
• Having a weakened immune system
• Travel to areas where giardiasis is common

When to see a doctor

See a doctor urgently if:

• You have signs of dehydration that are getting worse
• You cannot keep fluids down
• You have blood in your stool
• You have a high fever or severe belly pain
• You feel very weak, dizzy, or confused

Book a routine appointment if:

• Mild diarrhea that lasts more than 1 to 2 weeks
• Symptoms that keep coming back
• Weight loss or poor appetite
• You live with or care for someone who has giardiasis
• You drank untreated water and then became unwell

Diagnosis

Your healthcare provider will ask about your symptoms, travel, water exposure, and contacts, and may examine you. They may ask for stool samples to look for the Giardia parasite. Giardia can be missed in a single sample, so more than one sample may be needed.

Tests that may be done

• Stool sample tests to look for the parasite
• Antigen tests that detect parts of the parasite in stool
• PCR tests that look for the parasite's genetic material
• Sometimes repeat stool tests if symptoms continue

What to expect at your appointment

You may collect stool samples at home and return them as instructed. Results can take a few days. If tests are negative but symptoms continue, your provider may repeat tests or look for other causes.

Treatment

Most people with giardiasis need plenty of fluids and rest. A healthcare provider may also prescribe medicine to clear the parasite. Treatment helps reduce symptoms and lowers the chance of spreading the infection to others.

Self-care at home

• Drink fluids often. Oral rehydration drinks can help replace salts and sugar lost through diarrhea.
• Eat small, simple meals as you feel able.
• Rest until you feel stronger.
• Wash your hands often with soap and water.
• Avoid preparing food for others while you have diarrhea, if possible.
• Do not swim in pools, lakes, or rivers until a healthcare provider says it is safe — often at least 2 weeks after diarrhea stops.

Medical treatments

A healthcare provider may prescribe a medicine that targets the Giardia parasite. They will decide whether you need it based on your symptoms, health, pregnancy status, and local guidance. Take it exactly as instructed and finish the course. Do not use leftover medicines or someone else's medicine. Some mild infections may settle with fluids and rest, but treatment is often recommended to clear the infection and reduce spread.

When is surgery considered?

Surgery is not used to treat giardiasis. If you have another bowel problem, your provider will discuss any needed tests or procedures.

Living with this condition

You may feel tired and have loose stools for a while. Keep up fluids and hand hygiene, and return to normal activities when you feel ready and your provider says it is safe.

Lifestyle tips

• Wash hands with soap and water after using the toilet, changing diapers, and before preparing food.
• Avoid sharing towels, cups, or utensils while you are ill.
• Clean bathroom surfaces regularly.
• Stay off work or school until advised — many workplaces and childcare settings ask for at least 48 hours after the last diarrhea.
• Avoid swimming for at least 2 weeks after your last episode of diarrhea.

Diet and exercise

Eat simple foods as tolerated. There is no special diet that cures Giardia. Avoid alcohol and very fatty or spicy foods if they make symptoms worse. Return to exercise gently when you feel able and are drinking well.

Mental health and emotional wellbeing

Diarrhea and feeling unwell can be tiring and isolating. It is normal to feel worried about spreading the infection or about symptoms lasting. If you feel very low, anxious, or overwhelmed, talk to your healthcare provider. If you are in crisis, contact your local crisis support service or emergency number.

Prevention

Yes. You can lower the risk by washing your hands well, drinking safe water, washing fruit and vegetables, and avoiding swallowing water from lakes, rivers, streams, or pools.

Vaccines

There is no vaccine for giardiasis.

Screening programmes

Routine screening is not recommended. Testing is done if you have symptoms or a known exposure.

Complications

If left untreated

• Dehydration, especially in young children and older adults
• Long-lasting diarrhea and tiredness
• Weight loss and poor absorption of nutrients
• Lactose intolerance (trouble digesting milk sugars) that may last for a while
• Poor growth in children if the infection continues

Long-term outlook

The outlook is good for most people. Giardiasis can usually be cleared with fluids, rest, and medicine when needed. Some people feel tired or have loose stools for a while after treatment. If symptoms continue, go back to your provider.

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