What is Giardia?

Giardiasis is an infectious diarrhoeal disease caused by a protozoan parasite, Giardia lamblia. The parasite lives in the digestive tract of people and animals and is spread through faecal matter.  The parasite is able to survive outside the body by forming a cyst which protects it from the environment.  Giardia affects three times more children than adults, possibly because many individuals seem to have a lasting immunity after infection, and also because children do not have well developed personal hygiene.

What are the symptoms?

The usual interval between infection and the onset of acute symptoms ranges from several days to two weeks - usually 7 to 10 days. In most instances, the individual will experience:

  • Sudden explosive, watery, foul-smelling diarrhoea
  • Excessive gas
  • Abdominal pain
  • Bloating
  • Nausea
  • Tiredness
  • Loss of appetite
  • Occasionally fever and vomiting.

The symptoms usually last 7-10 days but approximately 50% of infected people have very mild symptoms or no symptoms at all. 


How are people infected?

 The parasite is transmitted from person to person through contact with infected faeces, either directly (such as between children) or indirectly via contaminated food, water and inanimate objects.

People become infected when they swallow the cysts which have been shed in an infected person's or animal's faeces. Common causes include:

  • Eating food prepared by infected people
  • Drinking from a poor quality water supply e.g. roof or stream water
  • Contact with pets, especially puppies and kittens with diarrhoea
  • Contact with manure from farm animals
  • Contact with infected people, including children and babies.


How is it treated?

Rest and extra fluid are recommended. Your doctor can prescribe a treatment for giardia.

Without treatment individuals with weakened immune systems may have the illness for months, or even years, causing recurrent mild or moderate symptoms such as impaired digestion, lactose intolerance, intermittent diarrhoea, tiredness, weakness, and significant weight loss.

How do I protect myself and others?

  • Make sure your house is connected to a Council water supply of good quality. If this is not possible use a treatment system that is rated to protect against Giardia.
  • If you have had Giardia you must stay out of swimming pools and spa pools until you have been free from all symptoms for two weeks.
  • Avoid contact with infants, very elderly or ill people while you have diarrhoea.
  • Use sodium hypochlorite (chlorine bleach) to clean your toilet and bathroom fixtures.  Remember that the Giardia cysts are resistant to most cleaning products. 

Wash your hands:

  • After going to the toilet or changing nappies
  • After playing or working with animals
  • Before handling food.


Do I need to take time off work, school or preschool?

  • Stay away from work, school or preschool when you have diarrhoea. 
  • Staff and children of early childhood centres should not return until they have been free from all symptoms for 48 hours.
  • People who work with food or in healthcare should not return until they have been free from all symptoms for 48 hours.


For more information about this illness contact a Health Protection Officer on 0800 221 555.