Giardia

Giardia
Kingdom	Protista
Sub-kingdom	Biciliata
Phylum	Metamonada
Super-class	Eopharyngea
Class	Trepomonadea
Sub-class	Diplozoa
Order	Giardiida
Family	Diplomonadidae
Genus	Giardia

Giardia lamblia life cycle - Wikimedia Commons

Giardia lamblia - Janice Carr

Giardia - Joaquim Castellà Veterinary Parasitology Universitat Autònoma de Barcelona

Giardia cyst - Courtesy of the Laboratory of Parasitology, University of Pennsylvania School of Veterinary Medicine

Overview

These protozoan parasite are found in humans as well as wild and domestic animals. They are a common cause of severe diarrhoea as part of the clinical symptoms giardiasis.

Recognition

Giardia spp. are flagellate protozoa with 8 flagella, 6 of which emerge from the body and are used in motility. They are 15-20μm long, pear shaped with a flat ventral surface. The most unique feature of this protozoa is the presence of a large adhesive disk in the flat surface that is used for attaching to the intestinal mucosa.

Life Cycle

Simple and direct

Trophozoites attach to intestinal wall

Reproduce by binary fission

Form cysts of 10μm
- Multi-nucleate cysts formed intermittently
- Immediately infective when passed in faeces

Prepatent period of 5-6 days

Pathogenesis

Commonest cause of protozoal diarrhoea of man in the UK

Common in domesticated animals

Infections often asymptomatic in domestic animals
- Can cause villous atrophy leading to malabsorption
- Infection can persist for weeks to months if not treated

Epidemiology

Infection via direct oral-faecal route or through contaminated water source (water-borne)

Wild animals may act as a source of infection for humans
- E.g. Beavers

Divided into 7 species
- G. duodenalis most commonly infects humans
  - Some subspecies are zoonotic

Giardia Learning Resources
Vetstream To reach the Vetstream content, please select	Canis, Felis, Lapis or Equis
Flashcards Test your knowledge using flashcard type questions	Giardia Flashcards