Protozoan infections are parasitic diseases caused by organisms formerly classified in the kingdom Protozoa. They are usually contracted by either an insect vector or by contact with an infected substance or surface and include organisms that are now classified in the supergroups Excavata, Amoebozoa, SAR, and Archaeplastida.
Protozoan infections are responsible for diseases that affect many different types of organisms, including plants, animals, and some marine life. Many of the most prevalent and deadly human diseases are caused by a protozoan infection, including African sleeping sickness, amoebic dysentery, and malaria.
The species originally termed "protozoa" are not closely related to each other and only have superficial similarities (eukaryotic, unicellular, motile, though with exceptions). The terms "protozoa" (and protist) are usually discouraged in the modern biosciences. However, this terminology is still encountered in medicine. This is partially because of the conservative character of medical classification and partially due to the necessity of making identifications of organisms based upon morphology.
Within the taxonomic classification, the four protist supergroups (Amoebozoa, Excavata, SAR, and Archaeplastida) fall under the domain Eukarya. Protists are an artificial grouping of over 64,000 different single-celled life forms. This means that it is difficult to define protists due to their extreme differences and uniqueness. Protists are a polyphyletic [(of a group of organisms) derived from more than one common evolutionary ancestor or ancestral group and therefore not suitable for placing in the same taxon] a collection of organisms and they are unicellular, which means that they lack the level of tissue organization which is present in more complex eukaryotes. Protists grow in a wide variety of moist habitats and a majority of them are free-living organisms. In these moist environments, plankton and terrestrial forms can also be found.
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La toxoplasmose est une infection parasitaire dont l'agent est le protozoaire Toxoplasma gondii. Le parasite infecte le plus souvent des animaux à sang chaud, y compris l’être humain, mais son hôte définitif est un félidé (dont le chat fait partie). L'infection est asymptomatique dans la majorité des cas pour les sujets immunocompétents, ne présentant un risque sérieux que pour les femmes enceintes, les personnes séropositives au VIH et les sujets ayant un système de défense immunitaire affaibli.
Parasitic protozoa infecting humans have a staggering impact on public health, especially in the developing world. Furthermore, several protozoan species are major pathogens of domestic animals and have a considerable impact on food production. In many ins ...
2004
In this issue of Cell, Coppens and coworkers (Coppens et al., 2006) describe how Toxoplasma gondii, an obligate intracellular parasite, feeds on the host. Coppens et al. provide evidence that the parasite takes host cell endosomes and lysosomes hostage by ...
Elsevier2006
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Siderophores are iron chelators secreted by bacteria to scavenge iron(III) from their surrounding environment. They possess their own internalization pathway that is sufficiently unselective to be hijacked, making them suitable for Trojan Horse strategy ap ...