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.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.Cryptosporidiosis: Intestinal infection with organisms of the genus CRYPTOSPORIDIUM. It occurs in both animals and humans. Symptoms include severe DIARRHEA.Coccidia: A subclass of protozoans commonly parasitic in the epithelial cells of the intestinal tract but also found in the liver and other organs. Its organisms are found in both vertebrates and higher invertebrates and comprise two orders: EIMERIIDA and EUCOCCIDIIDA.Eimeria: A genus of protozoan parasites of the subclass COCCIDIA. Various species are parasitic in the epithelial cells of the liver and intestines of man and other animals.Coccidiosis: Protozoan infection found in animals and man. It is caused by several different genera of COCCIDIA.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.Isospora: A genus of protozoan parasites found in the intestines of birds, amphibians, reptiles, and mammals, including man. The oocysts produce two sporocysts, each with four sporozoites. Many species are parasitic in wild and domestic animals.Parasite Egg Count: Determination of parasite eggs in feces.Feces: Excrement from the INTESTINES, containing unabsorbed solids, waste products, secretions, and BACTERIA of the DIGESTIVE SYSTEM.Parasitology: The study of parasites and PARASITIC DISEASES.Cyclospora: A genus of coccidian parasites in the family EIMERIIDAE. Cyclospora cayetanensis is pathogenic in humans, probably transmitted via the fecal-oral route, and causes nausea and diarrhea.Eucoccidiida: An order of parasitic protozoa found in blood cells and epithelial cells of vertebrates and invertebrates. Life cycles involve both sexual and asexual phases.Water Supply: Means or process of supplying water (as for a community) usually including reservoirs, tunnels, and pipelines and often the watershed from which the water is ultimately drawn. (Webster, 3d ed)Water: A clear, odorless, tasteless liquid that is essential for most animal and plant life and is an excellent solvent for many substances. The chemical formula is hydrogen oxide (H2O). (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)DNA, Protozoan: Deoxyribonucleic acid that makes up the genetic material of protozoa.Water Purification: Any of several processes in which undesirable impurities in water are removed or neutralized; for example, chlorination, filtration, primary treatment, ion exchange, and distillation. It includes treatment of WASTE WATER to provide potable and hygienic water in a controlled or closed environment as well as provision of public drinking water supplies.Eimeriidae: A large family of parasites in the order EIMERIIDA. They cause COCCIDIOSIS in a number of vertebrates including humans.Filtration: A process of separating particulate matter from a fluid, such as air or a liquid, by passing the fluid carrier through a medium that will not pass the particulates. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Fresh Water: Water containing no significant amounts of salts, such as water from RIVERS and LAKES.Cyclosporiasis: Infection with parasitic protozoa of the genus CYCLOSPORA. It is distributed globally and causes a diarrheal illness. Transmission is waterborne.Eimeria tenella: A species of coccidian protozoa that mainly infects domestic poultry.Water Pollution: Contamination of bodies of water (such as LAKES; RIVERS; SEAS; and GROUNDWATER.)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.Disinfection: Rendering pathogens harmless through the use of heat, antiseptics, antibacterial agents, etc.Potassium Dichromate: Chromic acid (H2Cr2O7), dipotassium salt. A compound having bright orange-red crystals and used in dyeing, staining, tanning leather, as bleach, oxidizer, depolarizer for dry cells, etc. Medically it has been used externally as an astringent, antiseptic, and caustic. When taken internally, it is a corrosive poison.Toxoplasma: A genus of protozoa parasitic to birds and mammals. T. gondii is one of the most common infectious pathogenic animal parasites of man.Sporozoites: The product of meiotic division of zygotes in parasitic protozoa comprising haploid cells. These infective cells invade the host and undergo asexual reproduction producing MEROZOITES (or other forms) and ultimately gametocytes.Spores, Protozoan: A vegetative stage in the life cycle of sporozoan protozoa. It is characteristic of members of the phyla APICOMPLEXA and MICROSPORIDIA.Immunomagnetic Separation: A cell-separation technique where magnetizable microspheres or beads are first coated with monoclonal antibody, allowed to search and bind to target cells, and are then selectively removed when passed through a magnetic field. Among other applications, the technique is commonly used to remove tumor cells from the marrow (BONE MARROW PURGING) of patients who are to undergo autologous bone marrow transplantation.Isosporiasis: Infection with parasitic protozoa of the genus ISOSPORA, producing intestinal disease. It is caused by ingestion of oocysts and can produce tissue cysts.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)Anopheles: A genus of mosquitoes (CULICIDAE) that are known vectors of MALARIA.Cattle Diseases: Diseases of domestic cattle of the genus Bos. It includes diseases of cows, yaks, and zebus.Sewage: Refuse liquid or waste matter carried off by sewers.RNA, Ribosomal, 18S: Constituent of the 40S subunit of eukaryotic ribosomes. 18S rRNA is involved in the initiation of polypeptide synthesis in eukaryotes.Apicomplexa: A phylum of unicellular parasitic EUKARYOTES characterized by the presence of complex apical organelles generally consisting of a conoid that aids in penetrating host cells, rhoptries that possibly secrete a proteolytic enzyme, and subpellicular microtubules that may be related to motility.Mineral Waters: Water naturally or artificially infused with mineral salts or gases.Toxoplasmosis, Animal: Acquired infection of non-human animals by organisms of the genus TOXOPLASMA.Antibodies, Protozoan: Immunoglobulins produced in a response to PROTOZOAN ANTIGENS.Benzophenoneidum: An aniline dye used as a disinfectant and an antiseptic agent. It is weakly fluorescing and binds specifically to certain proteins.Cattle: Domesticated bovine animals of the genus Bos, usually kept on a farm or ranch and used for the production of meat or dairy products or for heavy labor.Chlorine Compounds: Inorganic compounds that contain chlorine as an integral part of the molecule.Rivers: Large natural streams of FRESH WATER formed by converging tributaries and which empty into a body of water (lake or ocean).Plasmodium berghei: A protozoan parasite of rodents transmitted by the mosquito Anopheles dureni.Unionidae: A family of freshwater mussels in the class BIVALVIA. They differ from ZEBRA MUSSELS in that they are larger and posses a larval stage called glochidia, which requires attachment to the GILLS or fins of particular species of FISHES.Propidium: Quaternary ammonium analog of ethidium; an intercalating dye with a specific affinity to certain forms of DNA and, used as diiodide, to separate them in density gradients; also forms fluorescent complexes with cholinesterase which it inhibits.Water Microbiology: The presence of bacteria, viruses, and fungi in water. This term is not restricted to pathogenic organisms.Antigens, Protozoan: Any part or derivative of any protozoan that elicits immunity; malaria (Plasmodium) and trypanosome antigens are presently the most frequently encountered.Staining and Labeling: The marking of biological material with a dye or other reagent for the purpose of identifying and quantitating components of tissues, cells or their extracts.