Giardia Lamblia (giardiasis): symptoms and treatment

Giardiasis is a condition caused by infection with the parasite Giardia lamblia (see photo), a cosmopolitan parasite. An infection with Giardia lamblia is seasonal; it mainly occurs in the late summer months and in autumn. Giardiasis is mainly seen in children between the ages of 5 and 14. In principle, giardiasis goes away on its own. Nevertheless, the policy is to treat everyone in whom the infection has been proven by faecal examination (examination of your stool).

  • What is giardiasis?
  • Infection with a parasite
  • Self-limiting
  • Causes
  • Infection
  • Reinfection
  • Poor hygiene
  • Incubation period
  • Symptoms of giardiasis
  • Not always symptoms
  • Diarrhea and abdominal cramps
  • More serious complaints
  • Examination and diagnosis
  • Giardiasis treatment
  • Prognosis


What is giardiasis?

Infection with a parasite

Giardiasis is a condition caused by infection with the worldwide parasite Giardia lamblia, also known as Giardia intestinalis or Giardia duodenalis. Giardiasis can be caused by, among other things, eating or drinking contaminated food or swimming in contaminated water. Giardiasis can occur at any age, but it is most commonly seen in children between the ages of 5 and 14. In the Netherlands there are many cases of giardiasis in the months of August, September and October. The parasite is sometimes responsible for small epidemics at daycare centers.


Symptoms of giardiasis include (voluminous) diarrhea, flatulence (wind), abdominal cramps and nausea. In some people, the parasite causes no symptoms. Giardiasis is normally self-limiting. Complaints can be treated with the drug metronidazole. This relieves the discomfort and prevents the further spread of this culprit.



Infection can occur through contact with feces in which the cysts of the parasite are present. Infection occurs via the fecal-oral route, i.e. from the feces to the mouth and this is possible via:

  • drinking or swimming in contaminated water;
  • (rarely) eating or drinking contaminated food;
  • close contact with an infected person.



The cyst bursts in the small intestine, releasing the parasite. This multiplies itself and attaches to the intestinal wall, irritating and damaging it. This leads to diarrhea and intestinal complaints. Cysts are formed in the intestine, which are then excreted in the feces. Thus, another infection can occur.

Poor hygiene

The risk of contamination is high, especially under poor hygienic conditions. In the Netherlands, epidemics that occur on a small scale in kindergartens, crèches and daycare centers are notorious. This is mainly due to the poor hygiene of small children.

Incubation period

The incubation period, which is the period between infection and the first clinical symptoms of the disease, is approximately one to three weeks. A handful of cysts is enough for infection. The cysts can survive for up to about three months in an aqueous environment and at not too high temperatures.

Symptoms of giardiasis

Not always symptoms

Of those infected, 30-50% show symptoms. In less than 10% these symptoms persist for a long time (e.g. chronic diarrhea). In the other cases, the infection is asymptomatic, but these carriers can continue to secrete cysts for up to six months and thus become a source of infection for others.

Fatigue / Source:

Diarrhea and abdominal cramps

There is no characteristic pattern of complaints that could indicate an infection with Giardia lamblia. Continuous, intermittent or not, (slushy or watery) diarrhea (without blood) is the most common complaint. The diarrhea symptoms may be accompanied by nausea, gas, abdominal cramps, abdominal distension, flatulence and sometimes also fever and vomiting. Periods with complaints can alternate with periods in which few or no complaints occur. In infants and babies, loss of appetite, vomiting, diarrhea and failure to thrive are common. Toddlers and preschoolers often complain of stomach aches and fatigue. They can seem a bit lethargic and lethargic. School-age children suffer from varying degrees of diarrhea, abdominal pain and constipation.

More serious complaints

In some cases, more serious complaints such as malabsorption occur. Nutrients are not sufficiently absorbed into the blood from the gastrointestinal tract. This is often accompanied by smelly, greasy stools and weight loss.

Examination and diagnosis

Since there is no typical pattern of complaints that could indicate an infection with Giardia lamblia, the diagnosis is generally made by fecal examination for parasites.

Giardiasis treatment

In principle, giardiasis is self-limiting. However, it is often considered wise to treat an infection with medication. This, for example, is to prevent family members from becoming infected with this troublemaker. The GP will prescribe an antibiotic (for example ‘metronidazole’), which will eliminate the parasite. General hygiene measures, such as washing hands before eating and sanitary hygiene, are important to prevent further contamination. This should be taken into account, especially at nurseries and nurseries.


The prognosis for patients with giardiasis is generally excellent. Most patients are asymptomatic and most infections are self-limited. Giardiasis is not associated with mortality except in rare cases of extreme dehydration, mainly in infants or malnourished children.
Several antibiotic agents are available with good efficacy rates to shorten the disease course, although drug resistance has been observed in clinical practice. Untreated, giardiasis can last for weeks.

read more

  • Diarrhea: symptoms, causes & stopping watery stools
  • Acute infectious diarrhea: causes, symptoms & treatment
  • Stomach flu: symptoms, cause, treatment and prevention
  • Abdominal pain in the lower abdomen: left/right, causes in men and women
  • Intestinal parasite Giardia: symptoms, cause and treatment
Scroll to Top