What is giardiasis?

Giardiasis is an infection of the small intestine caused by a parasite called giardia. It can cause long-lasting symptoms and serious problems, especially in children. It is a common disease worldwide.

What are the symptoms of giardiasis?

The most common symptoms are:

• diarrhoea, which may be pale, greasy and smelly
• stomach cramps or bloating
• excessive gas or flatulence (wind)
• nausea
• fatigue
• weight loss

Symptoms of giardiasis start 3 to 25 days after infection with the parasite. They may last for months, especially if left untreated.

Some people do not develop symptoms, but they can still pass the disease on to others.

When should I see my doctor?

If you or your child has symptoms of giardiasis, see your doctor. This is especially important if you have diarrhoea that is severe or doesn't go away.

If your child is vomiting or has diarrhoea and is not drinking enough fluid, take them to a doctor immediately.

If you have been near someone with giardiasis, you only need to see a doctor if you develop symptoms.

What causes giardiasis?

Giardiasis is caused by the parasite giardia duodenalis, also known as giardia lamblia or giardia intestinalis.

The parasite lives in the faeces (poo) of infected people or animals. You can catch giardiasis if you eat contaminated food, or if you put your hands or other objects in your mouth after they have come in contact with infected faeces.

Outbreaks are common in childcare centres if carers practice poor hygiene after changing nappies. Read more on good hand hygiene.

You can also be infected from drinking or swimming in contaminated water.

Some countries have poor water quality and food hygiene practices, so you need to be careful when visiting these countries. You should not drink untreated water from rivers or lakes anywhere.

Read more on food safety.

How is giardiasis diagnosed?

If your doctor thinks you may have giardiasis, they may send a sample of your stool (poo) to the lab to be tested for giardia.

How is giardiasis treated?

Many people with giardiasis get better without treatment. If your symptoms don't get better on their own, you may need to take antibiotics or medicine to treat parasite infections (known as anti-parasitics).

People with diarrhoea, especially babies and young children, need to drink plenty of fluids to avoid dehydration. Your doctor may recommend rehydration therapy of glucose or an electrolyte solution. You can use diluted fruit juice for children who refuse to drink this solution.

Read more about avoiding dehydration in children.

What are the complications of giardiasis?

Having a giardia infection for a long time can cause long-term effects, such as weight loss or malnutrition, and possibly poor growth and development in children.

Some people develop lactose intolerance after having giardiasis. This usually goes away by itself.

Can giardiasis be prevented?

To help prevent the spread of giardia, always practice good personal hygiene — for example:

• Wash hands properly, especially after going to the toilet, before handling food and after every nappy change.
• Do not share linen, towels or eating utensils with other people who have symptoms.
• Boil water before drinking if you think it might be contaminated.
• Keep infected people from childcare, pre-school, school or work until they have not had any diarrhoea for at least 24 hours. If you work in the food industry, don't go back to work until you have had no diarrhoea or vomiting for 48 hours.
• Do not use swimming pools for at least 2 weeks after diarrhoea has completely stopped.

Treating infected people reduces the spread of the giardia parasite.

Resources and support

If you are worried about giardiasis, you can call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available 24 hours a day, 7 days a week.

If your baby or child has diarrhoea or is unwell, you can call Pregnancy, Birth and Baby to speak to a maternal child health nurse on 1800 882 436 or video call. Available from 7 am to midnight (AET), 7 days a week (including public holidays).

Read what to do if you get food poisoning at the Food Safety Information Council.

Looking for information for Aboriginal and/or Torres Strait Islander people?

The Food Safety Information Council has information on Aboriginal and Torres Strait Islander peoples and food safety.

Get tips to stay safe near water, including how to avoid flooded or contaminated water.

Read about the Aboriginal Communities Water and Sewerage Program in NSW.