Toxoplasma: A genus of protozoa parasitic to birds and mammals. T. gondii is one of the most common infectious pathogenic animal parasites of man.Toxoplasmosis: The acquired form of infection by Toxoplasma gondii in animals and man.Toxoplasmosis, Animal: Acquired infection of non-human animals by organisms of the genus TOXOPLASMA.Toxoplasmosis, Cerebral: Infections of the BRAIN caused by the protozoan TOXOPLASMA gondii that primarily arise in individuals with IMMUNOLOGIC DEFICIENCY SYNDROMES (see also AIDS-RELATED OPPORTUNISTIC INFECTIONS). The infection may involve the brain diffusely or form discrete abscesses. Clinical manifestations include SEIZURES, altered mentation, headache, focal neurologic deficits, and INTRACRANIAL HYPERTENSION. (From Joynt, Clinical Neurology, 1998, Ch27, pp41-3)Toxoplasmosis, Congenital: Prenatal protozoal infection with TOXOPLASMA gondii which is associated with injury to the developing fetal nervous system. The severity of this condition is related to the stage of pregnancy during which the infection occurs; first trimester infections are associated with a greater degree of neurologic dysfunction. Clinical features include HYDROCEPHALUS; MICROCEPHALY; deafness; cerebral calcifications; SEIZURES; and psychomotor retardation. Signs of a systemic infection may also be present at birth, including fever, rash, and hepatosplenomegaly. (From Adams et al., Principles of Neurology, 6th ed, p735)Antibodies, Protozoan: Immunoglobulins produced in a response to PROTOZOAN ANTIGENS.Protozoan Proteins: Proteins found in any species of protozoan.Toxoplasmosis, Ocular: Infection caused by the protozoan parasite TOXOPLASMA in which there is extensive connective tissue proliferation, the retina surrounding the lesions remains normal, and the ocular media remain clear. Chorioretinitis may be associated with all forms of toxoplasmosis, but is usually a late sequel of congenital toxoplasmosis. The severe ocular lesions in infants may lead to blindness.Antigens, Protozoan: Any part or derivative of any protozoan that elicits immunity; malaria (Plasmodium) and trypanosome antigens are presently the most frequently encountered.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.Sulfadiazine: One of the short-acting SULFONAMIDES used in combination with PYRIMETHAMINE to treat toxoplasmosis in patients with acquired immunodeficiency syndrome and in newborns with congenital infections.DNA, Protozoan: Deoxyribonucleic acid that makes up the genetic material of protozoa.Protozoan Vaccines: Suspensions of attenuated or killed protozoa administered for the prevention or treatment of infectious protozoan disease.Neospora: A genus of protozoan parasites of the subclass COCCIDIA. Its species are parasitic in dogs, cattle, goats, and sheep, among others. N. caninum, a species that mainly infects dogs, is intracellular in neural and other cells of the body, multiplies by endodyogeny, has no parasitophorous vacuole, and has numerous rhoptries. It is known to cause lesions in many tissues, especially the brain and spinal cord as well as abortion in the expectant mother.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.Chorioretinitis: Inflammation of the choroid in which the sensory retina becomes edematous and opaque. The inflammatory cells and exudate may burst through the sensory retina to cloud the vitreous body.Coccidiostats: Agents useful in the treatment or prevention of COCCIDIOSIS in man or animals.Pregnancy Complications, Parasitic: The co-occurrence of pregnancy and parasitic diseases. The parasitic infection may precede or follow FERTILIZATION.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.Spiramycin: A macrolide antibiotic produced by Streptomyces ambofaciens. The drug is effective against gram-positive aerobic pathogens, N. gonorrhoeae, and staphylococci. It is used to treat infections caused by bacteria and Toxoplasma gondii.Antiprotozoal Agents: Substances that are destructive to protozoans.Genes, Protozoan: The functional hereditary units of protozoa.Seroepidemiologic Studies: EPIDEMIOLOGIC STUDIES based on the detection through serological testing of characteristic change in the serum level of specific ANTIBODIES. Latent subclinical infections and carrier states can thus be detected in addition to clinically overt cases.Immunoglobulin M: A class of immunoglobulin bearing mu chains (IMMUNOGLOBULIN MU-CHAINS). IgM can fix COMPLEMENT. The name comes from its high molecular weight and originally being called a macroglobulin.Immunoglobulin G: The major immunoglobulin isotype class in normal human serum. There are several isotype subclasses of IgG, for example, IgG1, IgG2A, and IgG2B.Organelles: Specific particles of membrane-bound organized living substances present in eukaryotic cells, such as the MITOCHONDRIA; the GOLGI APPARATUS; ENDOPLASMIC RETICULUM; LYSOSOMES; PLASTIDS; and VACUOLES.Life Cycle Stages: The continuous sequence of changes undergone by living organisms during the post-embryonic developmental process, such as metamorphosis in insects and amphibians. This includes the developmental stages of apicomplexans such as the malarial parasite, PLASMODIUM FALCIPARUM.Enzyme-Linked Immunosorbent Assay: An immunoassay utilizing an antibody labeled with an enzyme marker such as horseradish peroxidase. While either the enzyme or the antibody is bound to an immunosorbent substrate, they both retain their biologic activity; the change in enzyme activity as a result of the enzyme-antibody-antigen reaction is proportional to the concentration of the antigen and can be measured spectrophotometrically or with the naked eye. Many variations of the method have been developed.Interferon-gamma: The major interferon produced by mitogenically or antigenically stimulated LYMPHOCYTES. It is structurally different from TYPE I INTERFERON and its major activity is immunoregulation. It has been implicated in the expression of CLASS II HISTOCOMPATIBILITY ANTIGENS in cells that do not normally produce them, leading to AUTOIMMUNE DISEASES.Vacuoles: Any spaces or cavities within a cell. They may function in digestion, storage, secretion, or excretion.Parasites: Invertebrate organisms that live on or in another organism (the host), and benefit at the expense of the other. Traditionally excluded from definition of parasites are pathogenic BACTERIA; FUNGI; VIRUSES; and PLANTS; though they may live parasitically.Coccidiosis: Protozoan infection found in animals and man. It is caused by several different genera of COCCIDIA.Cat Diseases: Diseases of the domestic cat (Felis catus or F. domesticus). This term does not include diseases of the so-called big cats such as CHEETAHS; LIONS; tigers, cougars, panthers, leopards, and other Felidae for which the heading CARNIVORA is used.Encephalitis: Inflammation of the BRAIN due to infection, autoimmune processes, toxins, and other conditions. Viral infections (see ENCEPHALITIS, VIRAL) are a relatively frequent cause of this condition.Sarcocystis: A genus of protozoa found in reptiles, birds, and mammals, including humans. This heteroxenous parasite produces muscle cysts in intermediate hosts such as domestic herbivores (cattle, sheep, pigs) and rodents. Final hosts are predators such as dogs, cats, and man.