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.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.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.DNA, Protozoan: Deoxyribonucleic acid that makes up the genetic material of protozoa.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.Feces: Excrement from the INTESTINES, containing unabsorbed solids, waste products, secretions, and BACTERIA of the DIGESTIVE SYSTEM.RNA, Ribosomal, 18S: Constituent of the 40S subunit of eukaryotic ribosomes. 18S rRNA is involved in the initiation of polypeptide synthesis in eukaryotes.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.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.Parasitology: The study of parasites and PARASITIC DISEASES.Coccidiostats: Agents useful in the treatment or prevention of COCCIDIOSIS in man or animals.Parasite Egg Count: Determination of parasite eggs in feces.RNA, Protozoan: Ribonucleic acid in protozoa having regulatory and catalytic roles as well as involvement in protein synthesis.Protozoan Infections: Infections with unicellular organisms formerly members of the subkingdom Protozoa.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)Paromomycin: An oligosaccharide antibiotic produced by various STREPTOMYCES.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.Antibodies, Protozoan: Immunoglobulins produced in a response to PROTOZOAN ANTIGENS.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.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.Protozoan Proteins: Proteins found in any species of protozoan.Cattle Diseases: Diseases of domestic cattle of the genus Bos. It includes diseases of cows, yaks, and zebus.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.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)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.Propionibacterium acnes: A bacteria isolated from normal skin, intestinal contents, wounds, blood, pus, and soft tissue abscesses. It is a common contaminant of clinical specimens, presumably from the skin of patients or attendants.Antigens, Protozoan: Any part or derivative of any protozoan that elicits immunity; malaria (Plasmodium) and trypanosome antigens are presently the most frequently encountered.Disinfection: Rendering pathogens harmless through the use of heat, antiseptics, antibacterial agents, etc.Polymerase Chain Reaction: In vitro method for producing large amounts of specific DNA or RNA fragments of defined length and sequence from small amounts of short oligonucleotide flanking sequences (primers). The essential steps include thermal denaturation of the double-stranded target molecules, annealing of the primers to their complementary sequences, and extension of the annealed primers by enzymatic synthesis with DNA polymerase. The reaction is efficient, specific, and extremely sensitive. Uses for the reaction include disease diagnosis, detection of difficult-to-isolate pathogens, mutation analysis, genetic testing, DNA sequencing, and analyzing evolutionary relationships.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)Genes, Protozoan: The functional hereditary units of protozoa.Antiprotozoal Agents: Substances that are destructive to protozoans.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.Amebicides: Agents which are destructive to amebae, especially the parasitic species causing AMEBIASIS in man and animal.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.Antiparasitic Agents: Drugs used to treat or prevent parasitic infections.Genome, Protozoan: The complete genetic complement contained in a set of CHROMOSOMES in a protozoan.Host-Parasite Interactions: The relationship between an invertebrate and another organism (the host), one of which lives at the expense of the other. Traditionally excluded from definition of parasites are pathogenic BACTERIA; FUNGI; VIRUSES; and PLANTS; though they may live parasitically.Water Microbiology: The presence of bacteria, viruses, and fungi in water. This term is not restricted to pathogenic organisms.Polymorphism, Restriction Fragment Length: Variation occurring within a species in the presence or length of DNA fragment generated by a specific endonuclease at a specific site in the genome. Such variations are generated by mutations that create or abolish recognition sites for these enzymes or change the length of the fragment.IMP Dehydrogenase: An enzyme that catalyzes the dehydrogenation of inosine 5'-phosphate to xanthosine 5'-phosphate in the presence of NAD. EC 184.108.40.206.Water Pollution: Contamination of bodies of water (such as LAKES; RIVERS; SEAS; and GROUNDWATER.)Fresh Water: Water containing no significant amounts of salts, such as water from RIVERS and LAKES.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.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.Food Parasitology: The presence of parasites in food and food products. For the presence of bacteria, viruses, and fungi in food, FOOD MICROBIOLOGY is available.Sewage: Refuse liquid or waste matter carried off by sewers.Zoonoses: Diseases of non-human animals that may be transmitted to HUMANS or may be transmitted from humans to non-human animals.Chlorine Compounds: Inorganic compounds that contain chlorine as an integral part of the molecule.Genotype: The genetic constitution of the individual, comprising the ALLELES present at each GENETIC LOCUS.