Giardiasis

Last reviewed: 23 Aug 2023

Last updated: 29 Dec 2022

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.

Definition

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.[1][2] Children and immunocompromised hosts may present with weight loss and failure to thrive due to malabsorption.

History and exam

Key diagnostic factors

diarrhea
frequent belching

More key diagnostic factors

Other diagnostic factors

abdominal bloating and discomfort
malaise
weight loss
nausea and vomiting

Other diagnostic factors

Risk factors

contaminated water/food
domestic animals living in or around the house
hypogammaglobulinemia
young age
male sex
day-care center attendance
men having sex with men
recent antibiotic use

More risk factors

Diagnostic investigations

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
CBC

More 1st investigations to order

Investigations to consider

Lateral flow immunoassay (e.g., ImmunoCard STAT!)
string test (EnteroTest)
duodenal aspirates and biopsies

More investigations to consider

Treatment algorithm

ACUTE

nonpregnant adult or child

pregnant; first trimester

pregnant; second or third trimester

ONGOING

treatment failure or resistance

Contributors

Authors

Luther A. Bartelt, MD

Assistant Professor of Medicine

University of North Carolina School of Medicine

Division of Infectious Diseases

Chapel Hill

Disclosures

LAB has received funding support from the National Institutes of Health to support giardiasis research and royalties from text authorships (Wolters Kluwer) for chapters about Giardia. LAB is the author of two articles cited in this topic.

Acknowledgements

Dr Luther Bartelt would like to gratefully acknowledge Dr Fida Khan and Dr Musaddiq Waheed, previous contributors to this topic.

Disclosures

FK and MW declared that they had no competing interests.

Peer reviewers

Zana Nikolla, MD

Faculty of Medicine

University of Tirana

Tirana

Albania

Disclosures

ZN declares that she has no competing interests.

Rodney Adam, MD

Professor of Medicine and Immunobiology

University of Arizona

Tucson

Disclosures

RA declares that he has no competing interests.

Differentials
- Rotavirus gastroenteritis
- Functional diarrhea
- Celiac disease
More Differentials
Guidelines
- Adverse events associated with EGD and EGD-related techniques
- CDC yellow book: chapter 4 - travel-related infectious diseases: giardiasis
More Guidelines
Patient leaflets
Diarrhea in adults
More Patient leaflets
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Giardiasis

Summary

Definition

History and exam

Key diagnostic factors

Other diagnostic factors

Risk factors

Diagnostic investigations

1st investigations to order

Investigations to consider

Treatment algorithm

nonpregnant adult or child

pregnant; first trimester

pregnant; second or third trimester

treatment failure or resistance

Contributors

Authors

Luther A. Bartelt, MD

Disclosures

Acknowledgements

Disclosures

Peer reviewers

Zana Nikolla, MD

Disclosures

Rodney Adam, MD

Disclosures

Differentials

Guidelines

Patient leaflets

Log in or subscribe to access all of BMJ Best Practice

Log in or subscribe to access all of BMJ Best Practice

Log in to access all of BMJ Best Practice