|
Harrison's Principles of Internal Medicine, 18e
| Part 8. Infectious Diseases > Section 18. Protozoal Infections > |
Chapter 215. Protozoal Intestinal Infections and Trichomoniasis
Sections: Protozoal Infections, Trichomoniasis, Further Readings.
Topics Discussed: gastrointestinal infections and enterotoxigenic poisonings; parasitic diseases; parasitology.
Excerpt:"Giardia intestinalis (also known as G. lamblia or G. duodenalis) is a cosmopolitan protozoal parasite that inhabits the small intestines of humans and other mammals. Giardiasis is one of the most common parasitic diseases in both developed and developing countries worldwide, causing both endemic and epidemic intestinal disease and diarrhea.(Fig. 215-1) Infection follows the ingestion of environmentally hardy cysts, which excyst in the small intestine, releasing flagellated trophozoites (Fig. 215-2) that multiply by binary fission. Giardia remains a pathogen of the proximal small bowel and does not disseminate hematogenously. Trophozoites remain free in the lumen or attach to the mucosal epithelium by means of a ventral sucking disk. As a trophozoite encounters altered conditions, it forms a morphologically distinct cyst, which is the stage of the parasite usually found in the feces. Trophozoites may be present and even predominate in loose or watery stools, but it is the resistant cyst that survives outside the body and is responsible for transmission. Cysts do not tolerate heating, desiccation, or continued exposure to feces but do remain viable for months in cold fresh water. The number of cysts excreted varies widely but can..."
The content above is only an excerpt.
For full access, log into an existing user account below,
purchase an annual subscription, or
purchase a short-term subscription to the complete website.
|
|
|
|
Or
|
|
|
|