Protozoan Infections: Infections with unicellular organisms formerly members of the subkingdom Protozoa.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.Helminths: Commonly known as parasitic worms, this group includes the ACANTHOCEPHALA; NEMATODA; and PLATYHELMINTHS. Some authors consider certain species of LEECHES that can become temporarily parasitic as helminths.Helminthiasis: Infestation with parasitic worms of the helminth class.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.YemenAmoebozoa: A supergroup (some say phylum) of ameboid EUKARYOTES, comprising ARCHAMOEBAE; LOBOSEA; and MYCETOZOA.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.Entamoebiasis: Infection with amoebae of the genus ENTAMOEBA. Infection with E. histolytica causes DYSENTERY, AMEBIC and LIVER ABSCESS, AMEBIC.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.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.Feces: Excrement from the INTESTINES, containing unabsorbed solids, waste products, secretions, and BACTERIA of the DIGESTIVE SYSTEM.Cryptosporidiosis: Intestinal infection with organisms of the genus CRYPTOSPORIDIUM. It occurs in both animals and humans. Symptoms include severe DIARRHEA.Protozoan Infections, Animal: Infections with unicellular organisms formerly members of the subkingdom Protozoa. The infections may be experimental or veterinary.Prevalence: The total number of cases of a given disease in a specified population at a designated time. It is differentiated from INCIDENCE, which refers to the number of new cases in the population at a given time.Protozoan Proteins: Proteins found in any species of protozoan.DNA, Protozoan: Deoxyribonucleic acid that makes up the genetic material of protozoa.Ciliophora: A phylum of EUKARYOTES characterized by the presence of cilia at some time during the life cycle. It comprises three classes: KINETOFRAGMINOPHOREA; OLIGOHYMENOPHOREA; and POLYMENOPHOREA.Genes, Protozoan: The functional hereditary units of protozoa.RNA, Protozoan: Ribonucleic acid in protozoa having regulatory and catalytic roles as well as involvement in protein synthesis.Genome, Protozoan: The complete genetic complement contained in a set of CHROMOSOMES in a protozoan.