Giardia is a common NZ parasite. Kiwi Families has provided helpful articles on giardia and explains the signs and symptoms, treatment, risks & complications of the giardia stomach bug and how it is treated in children.

What is giardia?

Giardia are tiny parasites that live in infected water and cause abdominal pain and diarrhoea in humans. Once inside the human body the parasite adheres to the wall of the small intestine (the gut) where it feeds, multiplies millions of times, and causes damage and a bowel infection. Giardia is the most common intestinal parasite worldwide.

Giardia is now widespread in New Zealand in lakes, streams and rivers – which is why trampers are advised not to drink water from these places unless it has first been boiled or purified.

The Giardia parasites live in the small intestines of both humans and animals (cats, dogs, possums, cattle, sheep, rats) and are passed on in the faeces by way of small cysts. These cysts can live outside the human or animal body for months in the soil or water.

As well as being infected by drinking contaminated water, children can pick up giardia after patting an infected animal or through poor toilet hygiene. There are often outbreaks in daycare centres and schools, and the bug will spread quickly through a family group.

Sydney had a couple of major outbreaks of Giardia in the late nineties when people became infected from tap water. The parasite can also live in bore water, in rainwater tanks, in swimming pools, spas and wells. Travellers need to be especially aware of Giardia: in poorer countries it may be found in raw vegetables, salads, fruit salads, sandwiches, tap water and ice.

A Giardia infection can last for many months, though it normally runs for 4 – 6 weeks. The incubation period (from when first exposed to the parasite to when first symptoms appear) is 1 – 3 weeks. Without proper treatment, a person with Giardia will remain infectious for many months.

What are the signs and symptoms of giardia?

  • Foul smelling diarrhoea
  • Frequent loose pale bowel motions
  • Abdominal cramps
  • Wind and bloating
  • Nausea and vomiting
  • Fatigue
  • Headache
  • Slight Fever
  • Weight loss
  • In infants it can cause failure to thrive, as Giardia hinders the ability to absorb food

What is the treatment for giardia?

  • The doctor will want to send a sample of bowel motion to the laboratory for testing and definitive diagnosis
  • Treatment is with anti-protozoal drugs (not to be taken during pregnancy)
  • Sometimes a repeat dose of medication will be needed to fully clear the infection
  • If your child is particularly ill or takes a long time to get well, antibiotics may also be prescribed
  • Children and teachers can only return to school or day care centres once they have been symptom free for 2 days

Risks & complications of giardia infection

  • Dehydration – alert your doctor if you think your child is becoming dehydrated
  • Children who have suffered Giardia may fail to thrive or develop learning problems later
  • Some people have recurring intestinal problems for years after the infection
  • Some people may have Giardia without displaying any symptoms.

What can I do for my child at home with giardia?

  • Keep children home from school or daycare
  • Ensure they have plenty of fluids
  • Take care with nappies so you do not become infected
  • Teach children good hygiene – always washing hands after being in the toilet, after touching animals, before touching food and eating
  • Teach your children not to drink water from rivers, lakes, streams unless it has been treated
  • Teach your children to try and avoid swallowing when swimming in pools or lakes, rivers and streams
  • Carefully wash fruit and vegetables before eating
  • If you are pregnant and your child has Giardia, ensure the doctor is aware of this
This is an essential family health reference, covering over 100 common, important, potentially serious and often worrying symptoms and emergencies, such as headaches, chest pain, dizziness, fever, bleeding, tiredness or stress. This classic bestseller has now been completely revised and updated to include the latest information on how to care for your sick child.

Helpful Articles

For advice on when to call the doctor for a sick child see our Kiwi Families article Emergency Check List

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Kimberley Paterson is a writer and public relations expert living in Whangaparaoa. She had an initial career as a registered nurse and has spent the last 20 years writing about health and well-being.

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I have been diagnosed with having Gardia my husband is in the food processing business how does this impact him?

Sally @ Kiwi Families

Hi Tracy, how unfortunate that you’ve got Giardia! But actually it could be much worse for your husband – many other diseases would affect his work. Giardia is actually reasonably difficult to spread person-to-person; currently there is no requirement for him to be tested and cleared unless he specifically starts showing symptoms himself. He should be able to continue his business as usual, but with extra vigilance as to his own health. If he suspects he may need to be tested (and if he tests positive, there will be follow up from Public Health that will assist him with how… Read more »


Hi can anyone tell me if that gutter stuff that goes into tank water kills Giardia

Rochelle Gribble

Hi there, are you talking about Gutter Witch? I’ve consulted a water engineer who says that it’s unlikely to kill Giardia.



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