Giardiasis

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Última revisión: 17 Aug 2025

Última actualización: 03 Jan 2025

Giardiasis symptoms vary from asymptomatic passage of cysts to acute self-limiting diarrhea or chronic diarrhea. It is associated with growth restriction in children.

Diagnosis is by detection of cysts or trophozoites in a stool sample or by molecular-based detection of antigens or parasite-specific nucleic acids.

Microscopy with direct fluorescent antibody testing is the gold standard for diagnosing giardiasis.

Tinidazole, metronidazole, or nitazoxanide is recommended as first-line treatment.

Transmission is via the fecal-oral route. Personal hygiene is key to prevention.

Definición

Giardiasis is an enteric infection caused by a eukaryotic, flagellated, binucleated protozoan parasite called Giardia duodenalis (formerly known as Giardia lamblia or Giardia intestinalis).[1] First described in 1681, it is a major cause of diarrheal disease in human beings and other mammals.[2][3] Children and immunocompromised people may present with weight loss and faltering growth, or other developmental impairments, due to gut dysfunction and nutritional deficiencies.[4]

Anamnesis y examen

Principales factores de diagnóstico

diarrhea
frequent belching

Todos los datos

Otros factores de diagnóstico

abdominal bloating and discomfort
malaise
weight loss
nausea and vomiting

Todos los datos

Factores de riesgo

contaminated water/food
domestic animals living in or around the house
hypogammaglobulinemia
young age
male sex
day-care center attendance
oral-anal sexual contact
recent antibiotic use

Todos los datos

Pruebas diagnósticas

Primeras pruebas diagnósticas para solicitar

direct fluorescence antibody (DFA) test
enzyme-linked immunosorbent assay
nucleic acid amplification test, polymerase chain reaction of stool sample
stool microscopy
CBC

Todos los datos

Pruebas diagnósticas que deben considerarse

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

Todos los datos

Algoritmo de tratamiento

Agudo

nonpregnant adult or child

pregnant; first trimester

pregnant; second or third trimester

En curso

treatment failure or resistance

Colaboradores

Autores

Luther A. Bartelt, MD

Assistant Professor of Medicine

University of North Carolina School of Medicine

Division of Infectious Diseases

Chapel Hill

Divulgaciones

LAB is reimbursed by UpToDate for authorship. LAB has received funding from the National Institutes of Health. LAB is the author of two articles cited in this topic.

Agradecimientos

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.

Peer reviewer acknowledgements

BMJ Best Practice topics are updated on a rolling basis in line with developments in evidence and guidance. The peer reviewers listed here have reviewed the content at least once during the history of the topic.

Disclosures

Peer reviewer affiliations and disclosures pertain to the time of the review.

References

Our in-house evidence and editorial teams collaborate with international expert contributors and peer reviewers to ensure that we provide access to the most clinically relevant information possible.

Key articles

Center for Disease Control and Prevention. CDC Yellow Book 2024: health information for international travel. Section 5: travel-associated infections & diseases - giardiasis. May 2023 [internet publication].Full text

Centers for Disease Control and Prevention. Giardia: about Giardia infections. May 2024 [internet publication].Full text

Shane AL, Mody RK, Crump JA, et al. 2017 Infectious Diseases Society of America clinical practice guidelines for the diagnosis and management of infectious diarrhea. Clin Infect Dis. 2017 Nov 29;65(12):e45-80.Full text Abstract

Reference articles

A full list of sources referenced in this topic is available to users with access to all of BMJ Best Practice.

Differentials
- Rotavirus or other viral gastroenteritis
- Functional diarrhea
- Celiac disease
More Differentials
Guidelines
- CDC Yellow Book: health information for international travel - giardiasis
- Infectious diarrhea: guideline for investigation
More Guidelines
Patient information
Diarrhea in adults
More Patient information
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Giardiasis

Resumen

Definición

Anamnesis y examen

Principales factores de diagnóstico

Otros factores de diagnóstico

Factores de riesgo

Pruebas diagnósticas

Primeras pruebas diagnósticas para solicitar

Pruebas diagnósticas que deben considerarse

Algoritmo de tratamiento

nonpregnant adult or child

pregnant; first trimester

pregnant; second or third trimester

treatment failure or resistance

Colaboradores

Autores

Luther A. Bartelt, MD

Divulgaciones

Agradecimientos

Disclosures

Peer reviewers

Zana Nikolla, MD

Disclosures

Rodney Adam, MD

Disclosures

Peer reviewer acknowledgements

Disclosures

References

Key articles

Reference articles

A full list of sources referenced in this topic is available to users with access to all of BMJ Best Practice.

Differentials

Guidelines

Patient information

Log in or subscribe to access all of BMJ Best Practice

Log in or subscribe to access all of BMJ Best Practice

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