Giardia infection is an infection of the bowel caused by the parasite Giardia duodenalis, also known as Giardia lamblia or Giardia intestinalis. It is a single-celled organism found worldwide.
Although Giardia infection occurs in many animals including dogs, cats, sheep and cattle, there is still some uncertainty about the extent of disease transmission between people and animals.
Spread takes place when hands, objects or food become contaminated with faeces of infected people or animals, or by drinking contaminated water. The parasites must be taken in by mouth to cause infection. In institutions and preschool centres, person-to-person transmission may be a significant means of spreading the illness. Transmission can occur with some sexual practices where there is contact with faecal matter. Re-infection can occur.
While some people have no symptoms, the most common symptoms include:
Giardia infections do not usually cause fever or bloody diarrhoea.
The infection is diagnosed by examining the faeces by a microscope or using a PCR (polymerase chain reaction) test in a pathology laboratory.
(time between becoming infected and developing symptoms)
3 to 25 days or longer (usually 7 to 10 days).
(time during which an infected person can infect others)
For as long as the organism is present in the faeces (often months), whether or not the person is ill. A person with diarrhoea is more likely to spread infection, but an infected person without symptoms can still spread the parasite to others.
Treatment of an ill person with appropriate antibiotic medication relieves symptoms and usually makes the person non-infectious within a few days.
