Giardia lamblia: A species of parasitic EUKARYOTES that attaches itself to the intestinal mucosa and feeds on mucous secretions. The organism is roughly pear-shaped and motility is somewhat erratic, with a slow oscillation about the long axis.Giardia: A genus of flagellate intestinal EUKARYOTES parasitic in various vertebrates, including humans. Characteristics include the presence of four pairs of flagella arising from a complicated system of axonemes and cysts that are ellipsoidal to ovoidal in shape.Giardiasis: An infection of the SMALL INTESTINE caused by the flagellated protozoan GIARDIA LAMBLIA. It is spread via contaminated food and water and by direct person-to-person contact.Trophozoites: Cells or feeding stage in the life cycle of sporozoan protozoa. In the malarial parasite, the trophozoite develops from the MEROZOITE and then splits into the SCHIZONT. Trophozoites that are left over from cell division can go on to form gametocytes.Intestinal Diseases, Parasitic: Infections of the INTESTINES with PARASITES, commonly involving PARASITIC WORMS. Infections with roundworms (NEMATODE INFECTIONS) and tapeworms (CESTODE INFECTIONS) are also known as HELMINTHIASIS.Feces: Excrement from the INTESTINES, containing unabsorbed solids, waste products, secretions, and BACTERIA of the DIGESTIVE SYSTEM.Protozoan Infections: Infections with unicellular organisms formerly members of the subkingdom Protozoa.Protozoan Proteins: Proteins found in any species of protozoan.Cryptosporidium parvum: A species of parasitic protozoa that infects humans and most domestic mammals. Its oocysts measure five microns in diameter. These organisms exhibit alternating cycles of sexual and asexual reproduction.Cryptosporidium: A genus of coccidian parasites of the family CRYPTOSPORIDIIDAE, found in the intestinal epithelium of many vertebrates including humans.Giardiavirus: A genus of RNA protozoan viruses of the family TOTIVIRIDAE. It infects many isolates of the flagellated protozoan human parasite G. lamblia, but does not seem to be associated with the virulence of the parasite. The type species is Giardia lamblia virus.Antiprotozoal Agents: Substances that are destructive to protozoans.Antigens, Protozoan: Any part or derivative of any protozoan that elicits immunity; malaria (Plasmodium) and trypanosome antigens are presently the most frequently encountered.DNA, Protozoan: Deoxyribonucleic acid that makes up the genetic material of protozoa.Cryptosporidiosis: Intestinal infection with organisms of the genus CRYPTOSPORIDIUM. It occurs in both animals and humans. Symptoms include severe DIARRHEA.Entamoeba histolytica: A species of parasitic protozoa causing ENTAMOEBIASIS and amebic dysentery (DYSENTERY, AMEBIC). Characteristics include a single nucleus containing a small central karyosome and peripheral chromatin that is finely and regularly beaded.Entamoeba: A genus of ameboid protozoa characterized by the presence of beaded chromatin on the inner surface of the nuclear membrane. Its organisms are parasitic in invertebrates and vertebrates, including humans.Genome, Protozoan: The complete genetic complement contained in a set of CHROMOSOMES in a protozoan.Gerbillinae: A subfamily of the Muridae consisting of several genera including Gerbillus, Rhombomys, Tatera, Meriones, and Psammomys.Metronidazole: A nitroimidazole used to treat AMEBIASIS; VAGINITIS; TRICHOMONAS INFECTIONS; GIARDIASIS; ANAEROBIC BACTERIA; and TREPONEMAL INFECTIONS. It has also been proposed as a radiation sensitizer for hypoxic cells. According to the Fourth Annual Report on Carcinogens (NTP 85-002, 1985, p133), this substance may reasonably be anticipated to be a carcinogen (Merck, 11th ed).Genes, Protozoan: The functional hereditary units of protozoa.Oocysts: Zygote-containing cysts of sporozoan protozoa. Further development in an oocyst produces small individual infective organisms called SPOROZOITES. Then, depending on the genus, the entire oocyst is called a sporocyst or the oocyst contains multiple sporocysts encapsulating the sporozoites.Spores, Protozoan: A vegetative stage in the life cycle of sporozoan protozoa. It is characteristic of members of the phyla APICOMPLEXA and MICROSPORIDIA.Triose-Phosphate Isomerase: An enzyme that catalyzes reversibly the conversion of D-glyceraldehyde 3-phosphate to dihydroxyacetone phosphate. A deficiency in humans causes nonspherocytic hemolytic disease (ANEMIA, HEMOLYTIC, CONGENITAL NONSPHEROCYTIC). EC 18.104.22.168.Dientamoeba: A genus of minute EUKARYOTES that are characterized by the preponderance of binucleate over uninucleate forms, the presence of several distinct granules in the karyosome, and the lack of a cystic stage. It is parasitic in the large intestine of humans and certain monkeys.Trichomonas vaginalis: A species of TRICHOMONAS that produces a refractory vaginal discharge in females, as well as bladder and urethral infections in males.Nitroreductases: Enzymes which reduce nitro groups (NITRO COMPOUNDS) and other nitrogenous compounds.Antigenic Variation: Change in the surface ANTIGEN of a microorganism. There are two different types. One is a phenomenon, especially associated with INFLUENZA VIRUSES, where they undergo spontaneous variation both as slow antigenic drift and sudden emergence of new strains (antigenic shift). The second type is when certain PARASITES, especially trypanosomes, PLASMODIUM, and BORRELIA, survive the immune response of the host by changing the surface coat (antigen switching). (From Herbert et al., The Dictionary of Immunology, 4th ed)Pyruvate Synthase: A ferredoxin-containing enzyme that catalyzes the COENZYME A-dependent oxidative decarboxylation of PYRUVATE to acetyl-COENZYME A and CARBON DIOXIDE.RNA, Protozoan: Ribonucleic acid in protozoa having regulatory and catalytic roles as well as involvement in protein synthesis.Entamoebiasis: Infection with amoebae of the genus ENTAMOEBA. Infection with E. histolytica causes DYSENTERY, AMEBIC and LIVER ABSCESS, AMEBIC.Dichlorophen: Nontoxic laxative vermicide effective for taenia infestation. It tends to produce colic and nausea. It is also used as a veterinary fungicide, anthelmintic, and antiprotozoan. (From Merck, 11th ed.)Diarrhea: An increased liquidity or decreased consistency of FECES, such as running stool. Fecal consistency is related to the ratio of water-holding capacity of insoluble solids to total water, rather than the amount of water present. Diarrhea is not hyperdefecation or increased fecal weight.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Parasitology: The study of parasites and PARASITIC DISEASES.Antibodies, Protozoan: Immunoglobulins produced in a response to PROTOZOAN ANTIGENS.Child Day Care Centers: Facilities which provide care for pre-school and school-age children.Dientamoebiasis: Gastrointestinal infection with organisms of the genus DIENTAMOEBA.Fluorescent Antibody Technique, Direct: A form of fluorescent antibody technique utilizing a fluorochrome conjugated to an antibody, which is added directly to a tissue or cell suspension for the detection of a specific antigen. (Bennington, Saunders Dictionary & Encyclopedia of Laboratory Medicine and Technology, 1984)Bithionol: Halogenated anti-infective agent that is used against trematode and cestode infestations.Diplomonadida: A group of flagellated, mostly symbiotic EUKARYOTES characterized by twofold symmetry associated with the presence of a pair of karyomastigont organellar systems. Two nuclei are attached by fibers to the flagella and there are no MITOCHONDRIA. Diplomonadida were formerly members of the class Zoomastigophora in the old five kingdom paradigm.Eukaryota: One of the three domains of life (the others being BACTERIA and ARCHAEA), also called Eukarya. These are organisms whose cells are enclosed in membranes and possess a nucleus. They comprise almost all multicellular and many unicellular organisms, and are traditionally divided into groups (sometimes called kingdoms) including ANIMALS; PLANTS; FUNGI; and various algae and other taxa that were previously part of the old kingdom Protista.