Giardiasis symptoms vary from asymptomatic passage of cysts to acute self-limiting diarrhea or chronic diarrhea. Association with growth restriction in children has been well described.
Diagnosis is by detection of cysts or trophozoites in a stool sample.
Tinidazole or metronidazole is recommended as first-line treatment.
Transmission is via the fecal-oral route. Personal hygiene is key to prevention.
Giardiasis is an enteric infection caused by a eukaryotic, flagellated, binucleated protozoan parasite called Giardia lamblia. First described in 1681, it is a major cause of diarrheal disease in human beings and other mammals. Children and immunocompromised hosts may present with weight loss and failure to thrive due to malabsorption.
History and exam
Key diagnostic factors
- frequent belching
Other diagnostic factors
- abdominal bloating and discomfort
- weight loss
- nausea and vomiting
- contaminated water/food
- domestic animals living in or around the house
- young age
- male sex
- day-care center attendance
- men having sex with men
- recent antibiotic use
1st investigations to order
- direct fluorescence antibody (DFA) test or enzyme-linked immunosorbent assay
- nucleic acid amplification test, polymerase chain reaction of stool sample
- stool microscopy
Investigations to consider
- Lateral flow immunoassay (e.g., ImmunoCard STAT!)
- string test (EnteroTest)
- duodenal aspirates and biopsies
pregnant; first trimester
pregnant; second or third trimester
treatment failure or resistance
Luther A. Bartelt, MD
Assistant Professor of Medicine
University of North Carolina School of Medicine
Division of Infectious Diseases
LAB declares that he has no competing interests. LAB is the author of two articles cited in this topic.
Dr Luther Bartelt would like to gratefully acknowledge Dr Fida Khan and Dr Musaddiq Waheed, previous contributors to this topic.
FK and MW declared that they had no competing interests.
Zana Nikolla, MD
Faculty of Medicine
University of Tirana
ZN declares that she has no competing interests.
Rodney Adam, MD
Professor of Medicine and Immunobiology
University of Arizona
RA declares that he has no competing interests.
- Rotavirus gastroenteritis
- Functional diarrhea
- Celiac disease
- CDC yellow book: chapter 4 - travel-related infectious diseases: giardiasis
- Practical guidance for clinical microbiology laboratories: laboratory diagnosis of parasites from the gastrointestinal tract
Diarrhea in adultsMore Patient leaflets
- Log in or subscribe to access all of BMJ Best Practice
Use of this content is subject to our disclaimer