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Learn about the life cycle, transmission, and symptoms of Giardia duodenalis, a protozoan flagellate that causes giardiasis. The cysts are resistant and infectious, and can be transmitted by water, food, or fecal-oral route.
- General Characteristics
- Life Cycle of Giardia lamblia
- Pathogenesis
- Clinical Findings
- Laboratory Diagnosis
Geographical distribution: worldwide; found in the soil, water, or surfaces contaminated with feces of infected human/animal.Habitat: Duodenum andupper part of jejunum of humans.Infection occurs by the ingestion of cysts in contaminated water, food, or by the fecal-oral route (hands or fomites)In the small intestine, excystation releases trophozoites (each cyst produces two trophozoites).Trophozoites multiply by longitudinal binary fission remaining in the lumen of the proximal small bowel where they can be free or attached to the mucosa by a ventral sucking disk.Encystation occurs as the parasites transit toward the colon.Many species of mammals, as well as humans, act as reservoirs.Risk groups:The trophozoite causes inflammation of the duodenal mucosa, leading to the malabsorption of protein and fat.Approximately half of those infected are asymptomatic carriers who continue to excrete the cyst for years.Giardiainfection can cause a variety of intestinal symptoms, which include; 1. Anorexia 2. Flatulence (gas) 3. Upset stomach or nausea/vomiting 4. Stomach or abdominal cramps 5. Watery (non-bloody), foul-smelling diarrhea 6. Greasy stools that tend to float 7. Dehydration (loss of fluids) Giardiasis can cause weight loss and failure to absorb fat, ...
Fecal specimens containing Giardia lambliamay have an offensive odor and are pale-colored, fatty, and float in water. 1. Ova and parasite (O+P) examination 1.1. Giardia cysts can be excreted intermittently, so many cases (>50%) of giardiasis will be missed with a single O+P examination, resulting in underdiagnosis. 1.2. Multiple stool collections (...
G. lamblia has two life stages: a motile, replicative trophozoite stage, in which the parasite survives in the small intestines of the host, and a nonreplicative cyst stage, in which the parasite survives in the environment.
- The Editors of Encyclopaedia Britannica
Feb 16, 2024 · Giardia has one of the simplest life cycles of all human parasites. The life cycle is composed of two stages: (1) the trophozoite (see the first image below), which exists freely in the...
Aug 11, 2021 · The life cycle of G. duodenalis consists of two stages, the trophozoite and cyst. The trophozoite is the vegetative form and replicates in the small intestine of the host. The eight flagella provide motility, and the ventral disk mediates attachment to the intestinal wall, where it gains its nutrients.
- Rodney D Adam
- 10.1128/CMR.00024-19
- 2021
- 2021/10
Giardia species have two major stages in the life cycle. Infection of a host is initiated when the cyst is ingested with contaminated water or, less commonly, food or through direct fecal-oral contact.
Jun 29, 2018 · The life cycle of Giardia species is simple and it is included of two active trophozoite and cystic forms. This parasite transmits via fecal-oral route through direct or indirect ingestion of infectious cysts. The incubation period varies from 9 to 15 days after ingestion of cysts.
