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A Giardia trophozoite, drawn by Vilém Lambl and published in 1859 Drawings of a Giardia trophozoite and cyst by Charles E. Simon in 1921. The first likely description of Giardia was in 1681 by Antonie van Leeuwenhoek, who in a letter to Robert Hooke, described "animalcules" resembling Giardia trophozoites in his stool.
A trophozoite (G. trope, nourishment + zoon, animal) is the activated, feeding stage in the life cycle of certain protozoa such as malaria-causing Plasmodium falciparum and those of the Giardia group. [1] The complementary form of the trophozoite state is the thick-walled cyst form. They are often different from the cyst stage, which is a ...
Infection with Giardia results in decreased expression of brush border enzymes, morphological changes to the microvillus, increased intestinal permeability, and programmed cell death of small intestinal epithelial cells. [22] Both trophozoites and cysts are contained within the gastrointestinal tract and do not invade beyond it. [23]
About 40 species have been described, but most of them are probably synonyms. [11] Currently, five to six morphologically distinct species are recognised. [12] Giardia duodenalis (=G. intestinalis, =G. lamblia) infect humans and other mammals, G. microti infects voles, G. muris is found in other mammals, G. ardeae and G. psittaci in birds, and G. agilis in amphibians. [4]
stool (diarrhea=ciliated trophozoite; solid stool=large cyst with horseshoe shaped nucleus) ingestion of cyst, zoonotic infection acquired from pigs (feces) Blastocystosis: Blastocystis spp. intestinal direct microscopy of stool (PCR, antibody) • worldwide: one of the most common human parasites [1] [2]
Due to the hard outer shell of the cyst, Cryptosporidium and Giardia are resistant to common disinfectants used by water treatment facilities such as chlorine. [15] In some protozoans, the unicellular organism multiplies during or after encystment and releases multiple trophozoites upon excystation.
Giardia intestinalis is a human pathogen, which is transmitted by cyst-contaminated water. It causes epidemic diarrhea from contaminated water. One can tell one may be infected by the observation of cysts or trophozoites in stools and ELISA (enzyme-linked immunosorbent assay) test. To prevent contamination, avoid any possibly contaminated water ...
The infectious dose of giardia, however, is very low, with about 2% chance of infection from a single cyst. [41] Also, very few studies have addressed the issue of transient contamination. According to one researcher, the likely model for the risk of Giardia from wilderness water is pulse contamination, that is, a brief period of high cyst ...