Giardiasis

Overview

Giardiasis (say 'jee-ar-DYE-uh-sis') is an infection of the small bowel caused by a tiny parasite called Giardia. You can't see it without a microscope. When you swallow it — usually in contaminated water or food — it settles in your gut and can cause diarrhoea, stomach cramps and bloating. It is not caused by being dirty or by eating badly. It is a common infection that can affect anyone, and it can be treated.

Yes, giardiasis is one of the more common gut infections caused by a parasite worldwide. It is seen in every country, but it is more common where clean water and good sanitation are harder to access, and in places where people live or work closely together, such as childcare settings.

Anyone can get giardiasis. It is especially common in young children and in people who care for them, people who travel to areas with untreated water, campers, hikers and swimmers who swallow water from lakes, rivers or streams, and people with weakened immune systems. Some people carry the parasite without feeling ill at all, but they can still pass it on to others.

Symptoms

Common symptoms

• Watery diarrhoea that may come and go over several days or weeks
• Greasy, pale, floating stools that are bulky and smell strongly
• Stomach cramps and bloating
• Wind and burping
• Feeling sick or being sick
• Feeling very tired
• Losing weight without trying
• Loss of appetite

Symptoms in children

• Loose, smelly stools, sometimes with mucus
• Poor feeding and slow weight gain, or losing weight
• Tummy pain and lots of wind
• Being irritable or more clingy than usual
• Nappy rash caused by frequent loose stools
• Less energy and playing less than usual
• Signs of dehydration, such as fewer wet nappies, a dry mouth or sunken eyes

Symptoms in older adults

• Diarrhoea that lasts longer than expected
• Feeling very tired and weak
• Weight loss and poor appetite
• Dehydration, which can come on faster in older bodies
• Confusion or drowsiness, which can be a sign of dehydration and needs medical advice
• Symptoms that flare up again after seeming to settle

Causes

Main causes

• Swallowing the Giardia parasite, which lives in the gut of infected people and animals and is passed out in poo
• Drinking untreated or poorly treated water, such as water from a well, stream, lake or tap water in areas where treatment is limited
• Eating food that was prepared or washed with contaminated water, or handled by someone who has the infection
• Swallowing water while swimming in pools, lakes, rivers or ponds that contain the parasite
• Close contact with someone who has giardiasis, especially in childcare settings or at home — for example, when changing nappies or helping a child to use the toilet, then not washing hands thoroughly
• Contact with infected animals, such as farm animals, puppies or kittens with diarrhoea — this is a less common route

Risk factors

• Travelling to places where water and sanitation are less reliable
• Camping, hiking or drinking from streams and rivers without treating the water
• Working in or attending a childcare setting, or having a young child at home
• Being a man who has sex with men
• Having a weakened immune system
• Living in shared housing or crowded places where an infection can spread easily
• Having close contact with someone who has gut symptoms, such as a household member

When to see a doctor

See a doctor urgently if:

• Diarrhoea that has lasted more than 7 days
• Blood or mucus in your stool
• A high fever or severe tummy pain
• Signs of dehydration, such as dizziness, a dry mouth, very little urine or dark urine
• Ongoing weight loss
• Diarrhoea in a baby, young child, older adult or someone with a weakened immune system
• Symptoms that come back after treatment

Book a routine appointment if:

• Loose, greasy or smelly stools that have persisted for a few days
• Bloating, wind and tummy cramps that keep coming back
• Tiredness and poor appetite alongside gut symptoms
• You have travelled or been camping recently, or been in close contact with someone who has similar symptoms
• You are unsure whether you need treatment

Diagnosis

The doctor will ask about your symptoms, your recent travel, your water sources, and anyone at home or at work with similar symptoms. They will usually ask you to provide a stool (poo) sample to be checked in a laboratory. Sometimes the first sample doesn't show the parasite, so you may be asked for more than one sample on different days. Giardiasis can look like other gut problems, so your doctor may also consider other causes before deciding on treatment.

Tests that may be done

• A stool sample that is tested for the parasite — this is the main test
• Sometimes two or three stool samples taken on different days, because the parasite can be missed in a single sample
• A stool test that looks for tiny traces of the parasite (an antigen test) or its genetic material (a PCR test) — these are often used in laboratories
• A blood test to check for signs of other conditions, if needed
• Rarely, if symptoms continue and tests are unclear, a specialist may suggest looking inside the bowel or referring you to a gut specialist

What to expect at your appointment

You will usually be given a small container and asked to bring back a sample of your stool. You can do this at home and drop it in as arranged. Laboratory results often take a few days. If your sample is negative but your symptoms continue, your doctor may ask for another sample or consider other tests. The whole process is routine and nothing to worry about — your healthcare team does these tests regularly.

Treatment

Giardiasis is treatable. Many people with mild symptoms get better on their own, but treatment can shorten the illness and reduce the chance of passing the parasite on to others. Treatment usually means drinking enough fluids, resting, and keeping up good hygiene, plus a prescription medicine to clear the parasite if your doctor thinks you need one.

Self-care at home

• Drink plenty of fluids to replace what you lose through diarrhoea — plain water is fine, and an oral rehydration solution (a powder from the pharmacy mixed with water) can help replace salts as well
• Take small, frequent sips if your stomach feels unsettled
• Eat plain, easy foods as you feel able — for example, rice, pasta, bread, bananas and potatoes — and avoid very rich or spicy food until you feel better
• Wash your hands with soap and warm water after using the toilet, before preparing food and after changing nappies
• Do not share towels, flannels or drinks while you are unwell
• Avoid swimming in pools, lakes or rivers for at least two weeks after your diarrhoea has stopped
• If you are a food handler, a carer or a healthcare worker, ask your employer or healthcare provider when it is safe to return to work
• Stay off work or school until 48 hours after your last episode of diarrhoea, unless a healthcare professional advises otherwise

Medical treatments

If your symptoms are troublesome or lasting, a doctor may prescribe a course of medicine to clear the parasite from your gut. These are short courses of tablets or liquid taken exactly as prescribed. It is important to finish the full course, even if you feel better early. Your doctor or pharmacist will explain what is being prescribed and how to take it, and will check whether it is suitable for you — for example, if you are pregnant, breastfeeding, or taking other medicines. Do not use leftover medicines or someone else's medicine. If you are dehydrated, your doctor may also recommend an oral rehydration solution and may arrange fluids through a drip in rare, more serious cases.

When is surgery considered?

Surgery is not used to treat giardiasis. This infection is treated with fluids, self-care and, where needed, prescription medicine.

Living with this condition

Most people feel better within a week or so of starting treatment, though tiredness and loose stools can take a little longer to settle. Keep an eye on your fluid intake, rest when your body asks for it, and keep washing your hands well — this protects you, your family and anyone who handles food with you. If you look after young children, wash your hands after every nappy change.

Lifestyle tips

• Keep up regular handwashing — it is the single most useful habit during and after the infection
• Clean bathroom surfaces and the toilet after use, especially if someone at home is also unwell
• Avoid preparing food for others while you have symptoms
• Make sure drinking water is safe — boil it or use a trusted filter when travelling or camping
• Wash fruit and vegetables with safe water, and peel them if you are unsure
• Avoid sharing towels, cups, bottles or cutlery while unwell

Diet and exercise

While you have diarrhoea, focus on fluids and plain, gentle foods. After the infection clears, you can gradually return to your usual diet. Some people find they are more sensitive to milk and dairy foods for a few weeks after giardiasis — this usually settles, but if it doesn't, your doctor can advise. When it comes to exercise, gentle movement is fine once you feel up to it, but give yourself time to recover, especially if you were dehydrated or lost weight.

Mental health and emotional wellbeing

Gut infections can be tiring and disruptive. Being anxious about symptoms, missing work or school, and worrying about passing the infection on is completely understandable. Most people make a full recovery, and these worries usually settle as symptoms ease. If you feel low, anxious or overwhelmed, tell your doctor or talk to someone you trust — support is available and you do not have to manage it alone.

Prevention

You can reduce the risk, though no single step removes it completely. The most effective habits are washing your hands often, drinking water from a safe source, and avoiding swallowing water when swimming.

Vaccines

There is no vaccine for giardiasis. Prevention rests on safe water, good hand hygiene and careful food handling.

Screening programmes

There is no routine screening for giardiasis. Testing is done when someone has symptoms, has been in close contact with an infection, or when a doctor thinks it is needed — for example, after travel or a known outbreak.

Complications

If left untreated

• Dehydration, which can be serious, particularly for babies, young children and older adults
• Ongoing diarrhoea and poor absorption of nutrients from food
• Weight loss and tiredness
• Slower growth or weight gain in children
• A temporary sensitivity to milk and dairy foods (lactose intolerance) that usually improves over weeks
• Rarely, longer-lasting gut symptoms such as bloating and loose stools
• Passing the infection on to family, friends or people you work closely with

Long-term outlook

The outlook is good. Most people recover fully, especially when they get treatment. Some people feel tired and find their gut sensitivity lingers for a few weeks, but this usually settles with time. The important thing is to keep drinking fluids and to get advice if symptoms are not clearing — you and your healthcare team can solve this together.

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